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Detergent

Detergent

A detergent is a compound, or a mixture of compounds, intended to assist cleaning. Such a substance, especially those made for use with water, may include any of various components having several properties:
- surfactants to 'cut' grease and to wet surfaces
- abrasives to scour
- substances to modify pH, either to affect performance or stability of other ingredients, or as caustics to destroy dirt
- water "softeners" to counteract the effect of "hardness" ions on other ingredients
- oxidants (oxidizers) for bleaching and destruction of dirt
- materials other than surfactants to keep dirt in suspension
- enzymes to digest proteins, fats, or carbohydrates in dirt or to modify fabric feel
- ingredients, surfactant or otherwise, modifying the foaming properties of the cleaning surfactants, to either stabilize or counteract foam plus ingredients having other properties to go along with detergency, such as optical brighteners, softeners, etc., and colors, perfumes, etc. Not only the material to be cleaned, but also the apparatus to be used, and type of and tolerance for dirt, dictate vast differences in the compositions of detergents. For instance, the following are all examples of glass-cleaning agents; however, they demonstrate the importance of context in the selection of an appropriate glass-cleaning agent:
- a chromic acid solution - to get glass very clean for certain precision-demanding purposes, namely in analytical chemistry,
- a high foaming mixture of surfactants with low skin irritation - for hand washing of drink glasses in a sink or dishpan,
- any of various non-foaming compositions - for glasses in a dishwashing machine,
- an ammonia-containing solution - for cleaning windows with no rinsing,
- windshield washer fluid - for a vehicle in motion. Sometimes the word "detergent" is used in distinction to "soap". For a while during the infancy of other surfactants as commercial detergent products, the term "syndet", short for "synthetic detergent" was promoted to indicate this, but never caught on too well, and is incorrect in any event because soap is itself synthesized via saponification of glycerides. The term "soapless soap" also saw a brief vogue. Unfortunately there is no accurate term for detergents not made of soap other than "soapless detergent" or "non-soap detergent". Also, the term "detergent" is sometimes used for surfactants in general, even when they are not used for cleaning. As can be seen above, this too is terminology that should be avoided as long as the term "surfactant" itself is available. Technically plain water, if used for cleaning, is a detergent. Probably the most widely used detergents other than water are soaps or mixtures composed chiefly of soaps. However, not all soaps have significant detergency. Often the word "soap" is used to indicate any detergent, especially those that have characteristics similar to those of soap; it's hard to beat a 4-letter word for popularity, even at the cost of precision.

Surfactant

: This article is about surfactants in general. For the compound produced by alveolar cells, see pulmonary surfactant. Surfactants, also known as wetting agents, lower the surface tension of a liquid, allowing easier spreading, and the interfacial tension between two liquids. The term surfactant is a contraction of "Surface active agent". Surfactants are usually organic compounds that are amphipathic, meaning they contain both hydrophobic groups (their "tails") and hydrophilic groups (their "heads"). Therefore, they are typically sparingly soluble in both organic solvents and water. Surfactants reduce the surface tension of water by adsorbing at the air-water interface. They also reduce the interfacial tension between oil and water by adsorbing at the liquid-liquid interface. Many surfactants can also assemble in the bulk solution into aggregates that are known as micelles. The concentration at which surfactants begin to form micelles is known as the critical micelle concentration or CMC. When micelles form in water, their tails form a core that is like an oil droplet, and their heads form an outer shell, or corona, that maintains favorable contact with water. When surfactants assemble in oil, the aggregate is referred to as a reverse micelle. In a reverse micelle, the heads are in the core and the tails maintain favorable contact with oil. In Index Medicus and the National Library of Medicine (NLM, USA Dept. of Health and Human Services), "surfactant" is reserved for the meaning pulmonary surfactant (see "alveoli" link below). For the more general meaning, "surface active agent" is the heading. Surfactants play an important role in many practical applications and products, including:
- detergents
- emulsifiers
- paints
- adhesives
- inks
- alveoli
- wetting
- foaming
- defoaming
- laxatives
- some herbicides A surfactant can be classified by the presence of formally charged groups in its head. A nonionic surfactant has no charge groups in its head. The head of an ionic surfactant carries a net charge. If the charge is negative, the surfactant is more specifically called anionic; if the charge is positive, it is called cationic. If a surfactant contains a head with two oppositely charged groups, it is termed zwitterionic. Some commonly encountered surfactants of each type include:
- Ionic
- Anionic (based on sulfonate anions or carboxylate anions)
- Soaps, or fatty acid salts (see acid salts)
- Sodium dodecyl sulfate (SDS), ammonium lauryl sulfate, and other alkyl sulfate salts
- Sodium laureth sulfate
- Cationic (based on quaternary ammonium cations)
- Cetyl trimethylammonium bromide (CTAB) and other alkyltrimethylammonium salts
- Cetyl pyridinium chloride
- polyethoxylated tallow amine (POEA)
- benzalkonium chloride
- Zwitterionic (amphoteric)
- Dodecyl betaine
- Dodecyl dimethylamine oxide
- Cocamidopropyl betaine
- Cocamide MEA, cocamide DEA, cocamide TEA
- Nonionic
- Alkyl poly(ethylene oxide)
- Alkyl polyglucosides, including:
- Octyl glucoside
- Decyl maltoside
- fatty alcohols
- cetyl alcohol
- oleyl alcohol Category:Colloidal chemistry Category:Cleaning product components Category:Surfactants ja:界面活性剤

Abrasive

An abrasive is usually a material that is used to smooth or to machine another softer material through extensive rubbing. Some common examples of abrasive objects are: :
- Borazon or Cubic Boron Nitride (CBN) :
- Carborundum :
- Coated abrasives :
- Diamond dust :
- Emery (mineral) (impure corundum) :
- Grinding wheel :
- Powdered glass :
- Pumice dust :
- Sand :
- Sandpaper Category:Manufacturing Category:Metalworking

PH

pH is a measure of the activity of hydrogen ions (H⁺) in a solution and, therefore, its acidity or alkalinity. In aqueous systems, the hydrogen ion activity is dictated by the dissociation constant of water (K_w) = 1.011 × 10⁻¹⁴ at 25 °C) and interactions with other ions in solution. Due to this dissociation constant a neutral solution (hydrogen ion activity equals hydroxide ion activity) has a pH of approximately 7. Aqueous solutions with pH values lower than 7 are considered acidic, while pH values higher than 7 are considered alkaline. The concept was introduced by S.P.L. Sørensen in 1909.

Definition

Though a pH value has no unit, it is not an arbitrary scale; the number arises from a definition based on the activity of hydrogen ions in the solution. The formula for calculating pH is: :

\mbox = -\log_ \left[ \mbox^+ \right]

[H⁺] denotes the activity of H⁺ ions (or more accurately written, [H₃O⁺], the equivalent hydronium ions), measured in moles per litre (also known as molarity). In dilute solutions (like river or tap water) the activity is approximately equal to the concentration of the H⁺ ion. Log₁₀ denotes the base-10 logarithm, and pH therefore defines a logarithmic scale of acidity. For example, a solution with pH=8.2 will have an [H⁺] activity (concentration) of 10^−8.2 mol/L, or about 6.31 × 10⁻⁹ mol/L; a solution with an [H⁺] activity of 4.5 × 10⁻⁴ mol/L will have a pH value of −log₁₀(4.5 × 10⁻⁴), or about 3.35. In aqueous solution at standard temperature and pressure (STP), a pH of 7 indicates neutrality (i.e. pure water) because water naturally dissociates into H⁺ and OH⁻ ions with equal concentrations of 1×10⁻⁷ mol/L. A lower pH value (for example pH 3) indicates increasing strength of acidity, and a higher pH value (for example pH 11) indicates increasing strength of alkalinity. Neutral pH is not exactly 7; this would imply that the H⁺ ion concentration is exactly 1×10⁻⁷ mol/L, which is not the case. The value is close enough, however, for neutral pH to be 7.00 to three significant figures, which is near enough for most people to assume it is exactly 7. In nonaqueous solutions or non-STP conditions, the pH of neutrality may not even be close to 7. Instead it is related to the dissociation constant for the specific solvent used. (Note also that pure water, when exposed to the atmosphere, will take in carbon dioxide, some of which reacts with water to form carbonic acid and H⁺, thereby lowering the pH to about 5.7.) Most substances have a pH in the range 0 to 14, although extremely acidic or basic substances may have pH < 0, or pH > 14.

Measuring

pH can be measured:

- by addition of a pH indicator into the studying solution. The indicator color varies depending on the pH of the solution. Using indicators, qualitative determinations can be made with universal indicators that have broad color variablity over a wide pH range and quantitative determinations can be made using indicators that have strong color variablitiy over a small pH range. Extremely precise measurements can be made over a wide pH range using indicators that have multiple equilibriums (ie H₂I) in conjunction with spectrophotometric methods to determine the relative abundance of each ph dependant component that make up the color of solution.
- by using a pH meter together with pH-selective electrodes (pH glass electrode, hydrogen electrode, quinhydrone electrode and other).

pOH

There is also pOH, in a sense the opposite of pH, which measures the concentration of OH⁻ ions. Since water self ionizes, and notating [OH⁻] as the concentration of hydroxide ions, we have :

K_ = \left[ \mbox^+ \right] \left[ \mbox^- \right] = 10^

(
- ) where K_w is the ionization constant of water. Now, since :

\log_K_ = \log_ \left[ \mbox^+ \right] + \log_ \left[ \mbox^- \right]

by logarithmic identities, we then have the relationship. :

-14 = \log_ \left[ \mbox^+ \right] + \log_ \left[ \mbox^- \right]

(
- ) and thus :

\mbox = -\log_ \left[ \mbox^- \right] = 14 + \log_ \left[ \mbox^+ \right] = 14 - \mbox

(
- ) (
- ) Valid exactly for temperature = 298.15 K (25 °C) only, acceptable for most lab calculations.

Calculation of pH for weak and strong acids

Values of pH for weak and strong acids can be approximated using certain assumptions. Under the Brønsted-Lowry theory, stronger or weaker acids are a relative concept. But here we define a strong acid as a species which is a much stronger acid than the hydronium (H₃O⁺) ion. In that case the dissociation reaction (strictly HX+H₂O↔H₃O⁺+X⁻ but simplified as HX↔H⁺+X⁻) goes to completion, i.e. no unreacted acid remains in solution. Dissolving the strong acid HCl in water can therefore be expressed: :HCl(aq) → H⁺ + Cl⁻ This means that in a 0.01 mol/L solution of HCl it is approximated that there is a concentration of 0.01 mol/L dissolved hydrogen ions. From above, the pH is: pH = −log₁₀ [H⁺]: :pH = −log (0.01) which equals 2. For weak acids, the dissociation reaction does not go to completion. An equilibrium is reached between the hydrogen ions and the conjugate base. The following shows the equilibrium reaction between methanoic acid and its ions: :HCOOH(aq) ↔ H⁺ + HCOO⁻ It is necessary to know the value of the equilibrium constant of the reaction for each acid in order to calculate its pH. In the context of pH, this is termed the acidity constant of the acid but is worked out in the same way (see chemical equilibrium): :K_a = [hydrogen ions][acid ions] / [acid] For HCOOH, K_a = 1.6 × 10⁻⁴ ([http://www.chembuddy.com/?left=BATE&right=dissociation_constants some other Ka values]) When calculating the pH of a weak acid, it is usually assumed that the water does not provide any hydrogen ions. This simplifies the calculation, and the concentration provided by water, 1×10⁻⁷ mol, is usually insignificant. With a 0.1 mol/L solution of methanoic acid (HCOOH), the acidity constant is equal to: :K_a = [H⁺][HCOO⁻] / [HCOOH] Given that an unknown amount of the acid has dissociated, [HCOOH] will be reduced by this amount, while [H⁺] and [HCOO⁻] will each be increased by this amount. Therefore, [HCOOH] may be replaced by 0.1 − x, and [H⁺] and [HCOO⁻] may each be replaced by x, giving us the following equation: :

1.6\times 10^ = \frac

Solving this for x yields 3.9×10⁻³, which is the concentration of hydrogen ions after dissociation. Therefore the pH is −log(3.9×10⁻³), or about 2.4.

Indicators

chemical equilibrium or blue, depending on soil pH. In acid soils the flowers will be blue, in alkaline soils the flowers will be pink [http://hgic.clemson.edu/factsheets/HGIC1067.htm] ]] An indicator is used to measure the pH of a substance. Common indicators are litmus paper, phenolphthalein, methyl orange, and bromothymol blue

References

- D. K. Nordstrom, C. N. Alpers, C. J. Ptacek, D. W. Blowes (2000). "Negative pH and Extremely Acidic Mine Waters from Iron Mountain, California." Environmental Science & Technology 34 (2), 254–258. (Available online: [http://dx.doi.org/10.1021/es990646v DOI] | [http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2000/34/i02/abs/es990646v.html Abstract] | [http://pubs.acs.org/cgi-bin/article.cgi/esthag/2000/34/i02/html/es990646v.html Full text (HTML)] | [http://pubs.acs.org/cgi-bin/article.cgi/esthag/2000/34/i02/pdf/es990646v.pdf Full text (PDF)]) Category:Acid-bases Category:Units of measure ko:수소 이온 농도 ja:水素イオン指数 simple:PH

Caustic

The word caustics has several meanings depending upon the context in which it is used:
- In Greek language, from which this word originates, caustics means "to burn" or "burning".
- In chemistry a caustic substance is one that 'eats away' or chemically burns other materials by process of attacking it basically (rather than acidically). Concentrated solutions of strong bases, such as the hydroxides of alkali metals and alkaline earth metals, are usually caustic. Caustic substances, such as drain cleaners, are harmful to living tissue.
- Caustic is also used as an abbreviation for "caustic soda", a common name for chemical compound sodium hydroxide (NaOH).
- In optics, a caustic is a bundle of light rays. For example a caustic effect may be seen when light refracts or reflects through some refractive or reflective material, to create a more focused, stronger light on the final location. Such amplification, especially of sunlight, can burn -- hence the name. A common situation when caustics are visible is when some light points on glass. There is a shadow behind the glass, but also there is a stronger light spot. Nowadays, almost every advanced rendering system supports caustics. Some of them even support volumetric caustics. This is accomplished by raytracing the possible paths of the light beam through the glass, accounting for the refraction, reflection, etc. Reference: Max Born and Emil Wolf, Optics.
- In differential geometry a caustic is the envelope of rays either reflected or refracted by a manifold. It is related to the optical concept of caustics.

Bleach

In chemistry, to bleach something generally means to whiten it or oxidize it. A bleach is a chemical that can produce these effects. Common chemical bleaches include sodium hypochlorite, or "chlorine bleach," and "oxygen bleach," which contains hydrogen peroxide or a peroxide-releasing compound (eg. sodium perborate, or sodium percarbonate). "Bleaching powder" is calcium hypochlorite. Bleaching can be a preliminary step in the process of dyeing. A bleaching agent, or bleach, is any compound that bleaches the colour out of fabrics, paper, or other materials. Household bleach or sodium hypochlorite is used in the home for whitening clothes, removing stains, and disinfecting. This is because sodium hypochlorite yields chlorine radicals—oxidizing agents readily reacting with many substances. Hair bleach contains H₂O₂ (hydrogen peroxide), which gives off oxygen radicals as it decomposes. Oxygen and chlorine radicals both have comparable bleaching effects. Chlorine bleach is often used with laundry detergent and is also commonly used as a disinfectant by homemakers and janitors. Mixing bleach and cleaners containing ammonia can create toxic chloramine gases and an explosive called nitrogen trichloride. Not all bleaches have to be of oxidizing nature. Sodium dithionite is used as a powerful reducing agent in some bleaching formulas. Chlorine dioxide is used for the bleaching of wood pulp, fats and oils, cellulose, flour, textiles, beeswax, and in a number of other industries. In the food industry, some organic peroxides (acetone peroxide, benzoyl peroxide, etc.) and other agents (e.g. bromates) are used as flour bleaching and maturing agents.

Photography

In most color negative processes, the silver halide crystals present in the emulsion are removed using chemical bleaches (unlike black and white negatives, which contain silver in all the dark areas). Photographic bleach is usually potassium ferricyanide.

Hazards

A problem with chlorine is that it reacts with organic material to form trihalomethanes like chloroform, which is a well known carcinogen. But the benefit of using chlorine to kill the germs in drinking water far outweighs any risk from the tiny trace of chloroform in treated drinking water. Chlorine is a respiratory irritant. It also attacks mucus membranes and burns the skin. As little as 3.5 ppm can be detected as an odor, and 1000 ppm is likely to be fatal after a few deep breaths. Exposure to chlorine should not exceed 0.5 ppm (8-hour time-weighted average - 40 hour week). Chlorine from typical CFCs like trichlorofluoromethane, which is stable, but reaches the ozone layer, is one of the two radicals formed there: the highly reactive chlorine atom, much more than the dichloromethyl radical, initiates the ozone degradation chain reaction. Category:Disinfectants ja:漂白剤

Enzyme

An enzyme is a protein that catalyzes, or speeds up, a chemical reaction. The word comes from the Greek ένζυμο, énsymo, which comes from én ("at" or "in") and simo ("leaven" or "yeast.") Enzymes are essential to sustain life because most chemical reactions in biological cells would occur too slowly, or would lead to different products, without enzymes. A malfunction (mutation, overproduction, underproduction or deletion) of a single critical enzyme can lead to a severe disease. For example, phenylketonuria is caused by a single amino acid mutation in the enzyme phenylalanine hydroxylase, which catalyses the first step in the degradation of phenylalanine. The resulting build-up of phenylalanine can lead to mental retardation, if the disease is untreated. Like all catalysts, enzymes work by lowering the activation energy of a reaction, thus allowing the reaction to proceed much faster. Enzymes may speed up reactions by a factor of many millions. An enzyme, like any catalyst, remains unaltered by the completed reaction and can therefore continue to function. Because enzymes, like all catalysts, do not affect the relative energy between the products and reagents, they do not affect equilibrium of a reaction. However, the advantage of enzymes compared to most other catalysts is their sterio-, regio- and chemoselectivity and specificity. Enzyme activity can be affected by other molecules. Inhibitors are naturally occuring or synthetic molecules that decrease or abolish enzyme activity; activators are molecules that increase the activity. Suicide inhibitors bind enzymes very tightly, effectively deactivating them. Many drugs and poisons act by inhibiting enzymes. Aspirin inhibits the COX-1 and COX-2 enzymes that produce the inflammation messenger prostaglandin, thus suppressing pain and inflammation. The poison cyanide inhibits cytochrome c oxidase, which effectively blocks cellular respiration. While all enzymes have a biological role, some enzymes are used commerically for other purposes. Many household cleaners use enzymes to speed up chemical reactions ( i.e., breaking down protein or starch stains in clothes). More than 5,000 enzymes are known. Typically the suffix -ase is added to the name of the substrate (e.g., lactase is the enzyme that catalyzes the cleavage of lactose) or the type of reaction (e.g., DNA polymerase catalyzes the formation of DNA polymers). However, this is not always the case, especially when enzymes modify multiple substrates. For this reason Enzyme Commission or EC numbers are used to classify enzymes based on the reactions they catalyze. Even this is not a perfect solution, as enzymes from different species or even very similiar enzymes in the same species may have identical EC numbers.

Etymology and history

EC numbers] The word enzyme comes from Greek: "in leaven". As early as the late 1700s and early 1800s, the digestion of meat by stomach secretions and the conversion of starch to sugars by plant extracts and saliva were observed. Studying the fermentation of sugar to alcohol by yeast, Louis Pasteur came to the conclusion that this fermentation was catalyzed by "ferments" in the yeast, which were thought to function only in the presence of living organisms. In 1897, Hans and Eduard Buchner inadvertently used yeast extracts to ferment sugar, despite the absence of living yeast cells. They were interested in making extracts of yeast cells for medical purposes, and, as one possible way of preserving them, they added large amounts of sucrose to the extract. To their surprise, they found that the sugar was fermented, even though there were no living yeast cells in the mixture. The term "enzyme" was used to describe the substance(s) in yeast extract that brought about the fermentation of sucrose.

3D-Structure

In enzymes, as with other proteins, function is determined by structure. An enzyme can be:
- A monomeric protein, i.e., containing only one polypeptide chain, typically one hundred or more amino acids; or
- an oligomeric protein consisting of several polypeptide chains, different or identical, that act together as a unit. As with any protein, each monomer is actually produced as a long, linear chain of amino acids, which folds in a particular fashion to produce a three-dimensional product. Individual monomers may then combine via non-covalent interactions to form a multimeric protein. amino acid Most enzymes are far larger molecules than the substrates they act on and that only a very small portion of the enzyme, around 10 amino acids, come into direct contact with the substrate(s). This region, where binding of the substrate(s) and then the reaction occurs, is known as the active site of the enzyme. Some enzymes contain sites thst bind cofactors, which are needed for catalysis. Certain enzymes have binding sites for small molecules, which are often direct or indirect products or substrates of the reaction catalyzed. This binding can serve to increase or decrease the enzyme's activity (depending on the molecule and enzyme), providing a means for feedback regulation.

Specificity

Enzymes are usually specific as to the reactions they catalyze and the substrates that are involved in these reactions. Shape, charge complementarity, and hydrophillic/hydrophobic character of enzyme and substrate are responsible for this specificity.

"Lock and key" hypothesis

substrate Enzymes are very specific and it was suggested by Emil Fischer in 1890 that this was because the enzyme had a particular shape into which the substrate(s) fit exactly. This is often referred to as "the lock and key" hypothesis. An enzyme combines with its substrate(s) to form a short-lived enzyme-substrate complex. Emil Fischer

Induced fit hypothesis

In 1958 Daniel Koshland suggested a modification to the "lock and key" hypothesis. Enzymes are rather flexible structures. The active site of an enzyme could be modified as the substrate interacts with the enzyme. The amino acids sidechains which make up the active site are molded into a precise shape which enables the enzyme to perform its catalytic function. In some cases the substrate molecule changes shape slightly as it enters the active site. A suitable analogy would be that of a hand changing the shape of a glove as the glove is put on.

Modifications

Many enzymes contain not only a protein part but need additionally various modifications. These modifications are made posttranslational, i.e., after the polypeptide chain was synthesized. Additional groups can be synthesized onto the polypeptide chain, e.g. phosphorylation or glycosylation of the enzyme. Another kind of posttranslational modification is the cleavage and splicing of the polypeptide chain. Chymotrypsin, a digestive protease, is produced in inactive form as chymotrypsinogen in the pancreas and transported in this form to the stomach where it is activated. This prevents the enzyme from harmful digestion of the pancreas or other tissue. This type of inactive precursor to an enzyme is known as a zymogen.

Enzyme cofactors

Some enzymes do not need any additional components to exhibit full activities. However, others require non-protein molecules to be bound for activity. Cofactors can be either inorganic (e.g., metal ions and Iron-sulfur clusters) or organic compounds, which are also known as coenzymes. Enzymes that require a cofactor, but do not have one bound are called apoenzymes. An apoenzyme together with its cofactor(s) constitutes a holoenzyme (i.e, the active form). Most cofactors are not covalently bound to an enzyme, but are closely associated. However, some cofactors known as prosthetic groups are covalently bound (e.g., heme in hemoglobin. Most cofactors are either regenerated or chemically unchanged at the end of the reactions. Many cofactors are vitamin-derivatives and serve as carriers to transfer electrons, atoms, or functional groups from an enzyme to a substrate. Common examples are NAD and NADP, which are involved in electron transfer and Coenzyme A, which is involved in the transfer of acetyl groups.

Allosteric modulation

Allosteric enzymes have either effector binding sites, or multiple protein subunits that interact with each other and thus influence catalytic activity.

Kinetics

In 1913, Leonor Michaelis and Maud Menten proposed a quantitative theory of enzyme kinetics which is still widely used today (usually referred to as Michaelis-Menten kinetics). Enzymes can perform up to several million catalytic reactions per second; to determine the maximum speed of an enzymatic reaction, the substrate concentration is increased until a constant rate of product formation is achieved. This is the maximum velocity (V_max) of the enzyme. In this state, all enzyme active sites are saturated with substrate. However, V_max is only one kinetic parameter that biochemists are interested in. The amount of substrate needed to achieve a given rate of reaction is also of interest. This can be expressed by the Michaelis-Menten constant (K_m), which is the substrate concentration required for an enzyme to reach one half its maximum velocity. Each enzyme has a characteristic K_m for a given substrate. Since V_max cannot be measured directly, both K_m and V_max are usually determined by extrapolating from a limited data set, using what is known as a double reciprocal, or Lineweaver-Burk plot. The efficiency of an enzyme can be expressed in terms of k_cat/K_m. The quantity k_cat, also called the turnover number, incorporates the rate constants for all steps in the reaction, and is the quotient of V_max and the total enzyme concentration. k_cat/K_m is a useful quantity for comparing different enzymes against each other, or the same enzyme with different substrates, because it takes both affinity and catalytic ability into consideration. The theoretical maximum for k_cat/K_m, called diffusion limit, is about 10⁸ to 10⁹ (M^-1 s^-1). At this point, every collision of the enzyme with its substrate will result in catalysis and the rate of product formation is not limited by the reaction rate but by the diffusion rate. Enzymes that reach this k_cat/K_m value are called catalytically perfect or kinetically perfect. Example of such enzymes are triose-phosphate isomerase, carbonic anhydrase, acetylcholinesterase, catalase, fumarase, ß-lactamase, and superoxide dismutase. The quantum-mechanical (physical) model of enzyme catalysis explains how certain enzymes worked faster than previously thought possible. This is achived by a process known as tunneling. While proposed in the early 1970s, it was not until 1989 that evidence of tunneling was found.

Thermodynamics

tunneling As with all catalysts, all reactions catalyzed by enzymes must be "spontaneous" (containing a net negative Gibbs free energy). With the enzyme, they run in the same direction as they would without the enzyme, just more quickly. However, the uncatalyzed, "spontaneous" reaction might lead to different products than the catalyzed reaction. Furthermore, enzymes can couple two or more reactions, so that a thermodynamically favorable reaction can be used to "drive" a thermodynamically unfavorable one. For example, the cleavage of the high-energy compound ATP is often used to drive other, energetically unfavorable chemical reactions. Many reactions catalyzed by an enzyme are reversible. :

\mathrm

Enzymes catalyze the forward and backward reactions equally. They do not alter the equilibrium itself, but only the speed at which it is reached, for example, carbonic anhydrase which catalyzes a reaction in either direction depending on the conditions at the time. :

\mathrm

(in tissues - high CO₂ concentration) :

\mathrm

(in lungs - low CO₂ concentration)

Inhibition

Enzymes reaction rates can be changed by competitive inhibition, non-competitive inhibition, uncompetitive inhibition and mixed inhibition.

Competitive inhibition

lung The inhibitor may bind to the substrate binding site as shown in the figure above, thus preventing substrate binding. An example for competitive inhibition is the enzyme succinate dehydrogenase by malonate. Succinate dehydrogenase catalyses the oxidation of succinate to fumarate. fumarate

Uncompetitive inhibition

Uncompetitive inhibition occurs when the inhibitor binds only to the enzyme-substrate complex, not to the free enzyme, the enzyme-inhibitor-substrate (EIS) complex is catalytically inactive. This mode of inhibition is rare.

Non-competitive inhibition

fumarate Non-competitive inhibitors never bind to the active center, but to other parts of the enzyme that can be far away from the substrate binding site, consequently, there is no competition between the substrate and inhibitor for the enzyme. The extent of inhibition depends entirely on the inhibitor concentration and will not be affected by the substrate concentration. However, these inhibitors bind only loosely with the enzyme and can be removed to resume the enzymatic activities. For example, cyanide combines with the copper prosthetic groups of the enzyme cytochrome c oxidase, thus inhibiting cellular respiration. By changing the conformation (the three-dimensional structure) of the enzyme, the inhibitors either disable the ability of the enzyme to bind or turn over its substrate. The EI and EIS-complex have no catalytic activity.

Partially competitive inhibition

The mechanism of partially competitive is similar to that of non-competitive inhibition, except that the EIS-complex has catalytic activity, which may be lower or even higher (partially competitive activation) than that of the ES-complex.

Irreversible inhibitors

Some inhibitors bind irreversibly with the enzyme molecules, inhibiting the catalytic activities permanently. The enzymatic reactions will stop sooner or later and are not affected by an increase in substrate concentration. These are irreversible inhibitors. Examples are heavy metal ions including silver, mercury and lead ions. Another example of irreversible inhibition is provided by the nerve gas diisopropylfluorophosphate (DFP) designed for use in warfare. It combines with the amino acid serine (contains the —OH group) at the active site of the enzyme acetylcholinesterase. The enzyme deactivates the neurotransmitter acetylcholine. Neurotransmitters are needed to continue the passage of nerve impulses from one neuron to another across the synapse. Once the impulse has been transmitted, acetylcholinesterase functions to deactivate the acetycholine almost immediately by breaking it down. If the enzyme is inhibited, acetylcholine accumulates and nerve impulses cannot be stopped, causing prolonged muscle contraction. Paralysis occurs and death may result since the respiratory muscles are affected. Some insecticides currently in use, including those known as organophosphates (e.g. parathion), have a similar effect on insects, and can also cause harm to nervous and muscular system of humans who are overexposed to them.

Metabolic pathways and allosteric enzymes

Several enzymes can work together in a specific order, creating metabolic pathways. In a metabolic pathway, one enzyme takes the product of another enzyme as a substrate. After the catalytic reaction, the product is then passed on to another enzyme. The end product(s) of such a pathway are often inhibitors for one of the first enzymes of the pathway (usually the first irreversible step, called committed step), thus regulating the amount of end product made by the pathways. Such a regulatory mechanism is called a negative feedback mechanism, because the amount of the end product produced is regulated by its own concentration. Negative feedback mechanism can effectively adjust the rate of synthesis of intermediate metabolites according to the demands of the cells. This helps with effective allocations of materials and energy economy, and it prevents the excess manufacture of end products. Like other homeostatic devices, the control of enzymatic action helps to maintain a stable internal environment in living organisms. homeostatic devices Enzymes that are regulated by end-production inhibition are usually allosteric enzymes. An allosteric enzyme molecule has an active site and also an allosteric site. The allosteric site can bind with allosteric effectors that affect the activity of the enzyme molecule. Allosteric effectors include allosteric activators and allosteric inhibitors. The binding with an allosteric activator activates an enzyme molecule because the active site is in the right conformation to bind with substrate molecules. The binding with an allosteric inhibitor inactivates the enzyme molecule because the conformation of the active site is altered. The activation and inhibition of an allosteric enzyme are reversible. homeostatic devices, the end product, is an allosteric inhibitor of ATCase.]]

Enzyme naming conventions

By common convention, an enzyme's name consists of a description of what it does, with the word ending in -ase. Examples are alcohol dehydrogenase and DNA polymerase. Kinases are enzymes that transfer phosphate groups. This results in different enzymes with the same function having the same basic name; they are therefore distinguished by other characteristics, such their optimal pH (alkaline phosphatase) or their location (membrane ATPase). Furthermore, the reversibility of chemical reactions means that the normal physiological direction of an enzyme's function may not be that observed under laboratory conditions. This can result in the same enzyme being identified with two different names: one stemming from the formal laboratory identification as described above, the other representing its behavior in the cell. For instance the enzyme formally known as xylitol:NAD+ 2-oxidoreductase (D-xylulose-forming) is more commonly referred to in the cellular physiological sense as D-xylulose reductase, reflecting the fact that the function of the enzyme in the cell is actually the reverse of what is often seen under in vitro conditions. The [http://www.iubmb.unibe.ch/ International Union of Biochemistry and Molecular Biology] has developed a nomenclature for enzymes, the EC numbers; each enzyme is described by a sequence of four numbers, preceded by "EC". The first number broadly classifies the enzyme based on its mechanism: The toplevel classification is
- EC 1 Oxidoreductases: catalyze oxidation/reduction reactions
- EC 2 Transferases: transfer a functional group (e.g. a methyl or phosphate group)
- EC 3 Hydrolases: catalyze the hydrolysis of various bonds
- EC 4 Lyases: cleave various bonds by means other than hydrolysis and oxidation
- EC 5 Isomerases: catalyze isomerization changes within a single molecule
- EC 6 Ligases: join two molecules with covalent bonds The complete nomenclature can be browsed at http://www.chem.qmul.ac.uk/iubmb/enzyme/

Industrial Applications

References

- Koshland D. The Enzymes, v. I, ch. 7, Acad. Press, New York, 1959
- Perutz M. Proc. Roy. Soc., B 167, 448, 1967
- M.V. Volkenshtein, R.R. Dogonadze, A.K. Madumarov, Z.D. Urushadze, Yu.I. Kharkats. Theory of Enzyme Catalysis.- Molekuliarnaya Biologia, Moscow, 6, 1972, pp. 431-439 (In Russian, English summary)
- Cha, Y., Murray, C. J. & Klinman, J. P. Science 243, 1325-1330 (1989).

External links

- [http://us.expasy.org/enzyme/ ExPASy enzyme database], links to Swiss-Prot sequence data, entries in other databases and to related literature searches
- [http://www.biochem.ucl.ac.uk/bsm/enzymes/ PDBsum] links to the known 3-D structure data of enzymes in the Protein Data Bank
- [http://www.brenda.uni-koeln.de BRENDA], comprehensive compilation of information and literature references about all known enzymes; requires payment by commercial users
- [http://bioinformatics.weizmann.ac.il/cards/ Weizmann Institute's Genecards Database], extensive database of protein properties and their associated genes.
- [http://drnelson.utmem.edu/CytochromeP450.html Cytochrome P450 enzymes] site lists over 4000 versions of enzymes from this cytochrome in plants and animals Category:Enzymes Category:Biochemistry Category:Metabolism ko:효소 ms:Enzim ja:酵素 simple:Enzyme th:เอนไซม์

Fat

Fat is one of the three main classes of food and, at approximately 38 kJ (9 kilocalories) per gram, as compared to sugar with 17 kJ (4 kcal) per gram or ethanol with 29 kJ (7 kcal) per gram, the most concentrated form of metabolic energy available to humans. (Note that 1 kcal = 1 "Calorie", capitalised in nutrition-related contexts.) Vitamins A, D, E, and K are fat-soluble meaning they can only be digested, absorbed, and transported in conjunction with fats. Fats are sources of essential fatty acids, an important dietary requirement. Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. They also serve as energy stores for the body. In food, there are two types of fats: saturated and unsaturated. Fats are broken down in the body to release glycerol and free fatty acids. The glycerol can be converted to glucose by the liver and thus used as a source of energy. The fatty acids are a good source of energy for many tissues, especially heart and skeletal muscle.

Adipose tissue

Adipose, or fatty, tissue is the human body's means of storing metabolic energy over extended periods of time. The location of the tissue determines its metabolic profile: "visceral fat" (around the abdomen) is prone to lead to insulin resistance, while "peripheral fat" (around the limbs) is much more harmless.

Metabolism

The metabolism of lipids is a closely regulated system in virtually all lifeforms. It is affected by a variety of enzymes and, in higher organisms, regulated by hormones. Research is ongoing on the relative influence of various hormonal regulators on the anabolism (production) and catabolism (breakdown, also termed lipolysis) of fatty molecules. A subject of particularly close study is cholesterol, levels and types of which are influenced by the fatty acid metabolism and is known for its role in development of atherosclerosis.

External link

- [http://www.scientificpsychic.com/fitness/fattyacids.html Chemical Structure of Fats and Fatty acids] Category:Lipids Category:Nutrition ja:脂肪 th:ไขมัน

References

Rebecca J. Donatelle. Health, The Basics. 6th ed. San Francisco: Pearson Education, Inc. 2005.

Carbohydrate

Carbohydrates are chemical compounds that contain oxygen, hydrogen, and carbon atoms. They consist of monosaccharide sugars of varying chain lengths and that have the general chemical formula C_n(H₂O)_n or are derivatives of such. Certain carbohydrates are an important storage and transport form of energy in most organisms, including plants and animals. Carbohydrates are classified by the number of sugar units into monosacchharides (such as glucose), disaccharides (such as saccharose), oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose).

Structure

cellulose)]] cellulose)]] Pure carbohydrates contain carbon, hydrogen, and oxygen atoms, in a 1:2:1 molar ratio, giving the general formula C_n(H₂O)_n. (This applies only to monosaccharides, see below, although all carbohydrates have the more general formula C_n(H₂O)_m.) However, many important "carbohydrates" deviate from this, such as deoxyribose and glycerol, although they are not, in the strict sense, carbohydrates. Sometimes compounds containing other elements are also counted as carbohydrates (e.g. chitin, which contains nitrogen). The simplest carbohydrates are monosaccharides, which are small straight-chain aldehydes and ketones with many hydroxyl groups added, usually one on each carbon except the functional group. Other carbohydrates are composed of monosaccharide units and break down under hydrolysis. These may be classified as disaccharides, oligosaccharides, or polysaccharides, depending on whether they have two, several, or many monosaccharide units..

Monosaccharides

Monosaccharides may be divided into aldoses, which have an aldehyde group on the first carbon atom, and ketoses, which typically have a ketone group on the second. They may also be divided into trioses, tetroses, pentoses, hexoses, and so forth, depending on how many carbon atoms they contain. For instance, glucose is an aldohexose, fructose a ketohexose, and ribose an aldopentose. Further, each carbon atom that supports a hydroxyl group (except for the first and last) is optically active, allowing a number of different carbohydrates with the same basic structure. For instance, galactose is an aldohexose but has different properties from glucose because the atoms are arranged differently. galactose) ]] The straight-chain structure described here is only one of the forms a monosaccharide may take. The aldehyde or ketone group may react with a hydroxyl group on a different carbon atom to form a hemiacetal or hemiketal, in which case there is an oxygen bridge between the two carbon atoms, forming a heterocyclic ring. Rings with five and six atoms are called furanose and pyranose forms and exist in equilibrium with the straight-chain form. It should be noted that the ring form has one more optically active carbon than the straight-chain form, and so has both an alpha and a beta form, which interconvert in equilibrium. However, the carbohydrate may further react with an alcohol to form an acetal or ketal, in which case the two forms become distinct. This is the basic type of link between the monosaccharide units of larger carbohydrates.

Disaccharides

Disaccharides are composed of two monosaccharide units bound together by a covalent glycosidic bond. The binding between the two sugars results in the loss of a hydrogen atom (H) from one molecule and a hydroxyl group (OH) from the other. The most common disaccharides are sucrose (cane or beet sugar - made from one glucose and one fructose), lactose (milk sugar - made from one glucose and one galactose) and maltose (made of two glucoses). The formula of these disaccharides is C₁₂H₂₂O₁₁.

Oligosaccharides and polysaccharides

Oligosaccharides and polysaccharides are composed of longer chains of monosaccharide units bound together by glycosidic bonds. The distinction between the two is based upon the number of monosaccharide units present in the chain. Oligosaccharides typically contain between three and nine monosaccharide units, and polysaccharides contain greater than ten monosaccharide units. Definitions of how large a carbohydrate must be to fall into each category vary however. Oligosaccharides are found as a common form of protein posttranslational modification. Polysaccharides represent an important class of biological polymer. Examples include starch, cellulose and chitin. Table and powdered sugar are some of the foods you find disaccharides in.

Nutrition

chitin Strictly speaking, carbohydrates are not necessary for human nutrition because proteins can be converted to carbohydrates—the traditional diet of some peoples consists of virtually no carbohydrate, and they are perfectly healthy. However, carbohydrates require less water to digest than proteins or fats and are an important source of energy. The (very) low carbohydrate diet is infamous for producing temporary “brain fog” because your brain and central nervous system function almost exclusively on glucose. Some problems have been cited for the long term effects of a no-carbohydrate diet for some individuals. Athletes, for instance, or those that participate in high intensity activities, will have a considerable reduction in performance, due to having little to no glycogen supplies stored in muscle tissue. Additionally, nephrotoxicity may occur, particularly in persons that are not very well hydrated. Some examples of different carbohydrate rich foods are beans, bread and pasta.

Catabolism

There are three major metabolic pathways of carbohydrate catabolism: # Glycolysis # Citric acid cycle

External links

- [http://www.chem.qmw.ac.uk/iupac/2carb/ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature (JCBN): Carbohydrate Nomenclature]
- [http://www.cem.msu.edu/~reusch/VirtualText/carbhyd.htm Carbohydrates detailed]
- [http://www.carbohydrate-counter.org/about-carbohydrates.php Carbohydrates Overview]
- [http://www.biochemweb.org/carbohydrates.shtml Carbohydrates and Glycosylation - The Virtual Library of Biochemistry and Cell Biology]
- [http://www.functionalglycomics.org/static/consortium/ Consortium for Functional Glycomics] Category:Carbohydrates Category:Nutrition ko:탄수화물 ja:炭水化物 th:คาร์โบไฮเดรต

Foam

The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. It can also refer to anything that is analogous to such a phenomenon, such as quantum foam. Often people mean polyurethane foam (foam rubber), Styrofoam or some other manufactured foam when they are using the term. From the early 20th century, various types of specially manufactured solid foams came into use. The low density of these foams made them excellent as thermal insulators and flotation devices, and their lightness and compressibility made them ideal as packing materials and stuffings. Some liquid foams also found uses in extinguishing fires, especially oil fires. Foam, in this case meaning "bubbly liquid", is also produced as an often unwanted by-product in the manufacture of various substances. For example, foam is a serious problem in the chemical industry, especially for biochemical processes. Many biological substances, for example proteins, easily create foam on agitation and/or aeration. Foam is a problem because it alters the liquid flow and blocks oxygen transfer from air (therefore preventing microbial respiration in fermentation processes). For this reason, antifoam compounds, like silicone oils, are added to prevent these problems. Foaming around the mouth can be a symptom of rabies in animals. The term sea foam is used to describe the foam that forms on top of seawater from the action of waves. In some ways, leavened bread is a foam, as the yeast causes the bread to rise by producing tiny bubbles of gas in the dough.

Structure of foams

Real-life foams are typically disordered and have a variety of bubble sizes. The study of idealised foams is closely linked to the mathematical problems of space-filling and minimal surfaces. The Weaire-Phelan structure is believed to be the best possible (optimal) unit cell of a perfectly ordered foam, while Plateau's Rules describe how the soap-films form structures in foams.

Types of manufactured foam

- acoustic foam
- anti-static foam
- closed cell foam - a firm type of foam
- Aerogel the world's lowest density solid
- Airex foam or FloTex foam
- Latex foam
- Microcellular plastic
- polychloroprene foam
- Neoprene
- polyethylene foam
- EVA foam or polyethylene vinyl acetate foam
- polyisocyanurate foam
- polystyrene foam
- Styrofoam
- polythene foam
- Syntactic foam, with extremely high compressive strength.
- fire retardant foam or CMHR (Combustion Modified High Resillient) foam
- open cell foam - a more breathable and flexible foam
- polyurethane foam
- memory foam
- metal foam
- SEAgel — an ultralight biodegradable foam used as an insulator
- spray foam Category:Materials

Foaming agent

A foaming agent is a material that will decompose to release a gas under certain conditions (typically high temperature), which can be used to turn a liquid into a foam. For Example, powdered titanium hydride is used as a foaming agent in the production of metal foams, as it decomposes to form titanium and hydrogen gas at elevated temperatures. See also: antifoaming agent category:materials

Optical brightener

Optical brighteners, optical brightening agents, fluorescent brightening agents or fluorescent whitening agents are dyes that absorb light in the ultraviolet and violet region of the electromagnetic spectrum, and re-emit light in the blue region. These additives are designed to enhance the appearance of colours in fabrics and on papers. They may also enhance or modify the appearance of white items. This creates a whitening effect by making materials look less yellow and by increasing the overall amount of light reflected to the eye. The most common class of chemicals with this property are the stilbenes. These chemicals are commonly part of laundry detergents to replace FWA removed during washing and enhance the appearance of garments. The molecules that make up these additives are fluorescent dyes such as umbelliferone, which absorb energy in the UV portion of the spectrum. This energy is then re-emitted in the blue portion of the visible spectrum. A white surface treated with an optical brightener emits more visible light than shines on it, making it appear brighter. The blue emitted hides yellow and brown tones, making treated materials appear whiter. Optical brighteners have replaced bluing which was formerly used to produce the same effect. The additives are commonly used in washing powders, detergents, and in paper manufacture, with the result that white paper and clothing show up as strongly fluorescent under UV illumination. Paper used for banknotes does not contain optical brighteners, so a common method for detecting forged notes is to check for fluorescence. Category:Dyes Category:Cleaning product components Category:Luminescence

Perfume

:For the book "Perfume" by Patrick Süskind, see Perfume (book). Perfume is a mixture of fragrant essential oils and aroma compounds, fixatives, and solvents used to give the human body, objects, and living spaces a lasting and pleasant smell. The amount and type of solvent mix with the fragrance oil dictates whether a perfume is considered a perfume extract, Eau de parfum, Eau de toilette, or Eau de Cologne. Eau de Cologne

Obtaining odorants

Before perfumes can be composed, the odorants used in various perfume compositions must first be obtained. Synthetic odorants are produced through organic synthesis and purified. Odorants from natural sources require the use of various methods to extract the aromatics from the raw materials. The results of the extraction are either essential oils, absolutes, concretes, or butters, depending on the amount of waxes in the extracted product.
- Distillation: A common technique for obtaining aromatic compounds from flowers, plants, and grasses, such as orange blossoms and roses. The raw material is placed in a distillation still with water and heated until the fragrant compounds are driven from the material and re-collected through condensation of the distilled vapour. The water used in distillation, which retains some of the fragrant compounds and oils from the raw material is called hydrosol.
- Maceration/Solvent extraction: The most commonly used and economically important technique for extracting aromatics in the modern perfume industry. Raw materials are submerged in a solvent that can dissolve the desired aromatic compounds. Maceration lasts anywhere from hours to months. Fragrant compounds for woody and fibrous plant materials are often obtained in this matter as are all aromatics from animal sources. The technique can also be used to extract odorants that are too volatile for distillation or easily denatured by heat. Commonly used solvents for maceration/solvent extraction include ethanol, hexane, and dimethyl ether.
- Expression: Raw material is squeezed or compressed and the oils are collected. Of all raw materials, only the fragrant oils from the peels of fruits in the citrus family are extracted in this manner since the oil is present in large enough quantities as to make this extraction method economically feasible.
- Enfleurage: Absorption of aroma materials into wax and then extracting the odorous oil with alcohol. Extraction by enfleurage was commonly used when distillation was not possible due to the fact that some fragrant compounds denature through high heat. This technique is not commonly used in the present day industry due to its prohibitive cost and the existence of more efficient and effective extraction methods.

Composing perfumes

Perfume oils usually contain tens to hundreds of ingredients. Included in the perfume are fixatives, which bind the various fragrances together, include balsams, ambergris, and secretions from the scent glands of civets and musk deer (undiluted, these have unpleasant smells but in alcoholic solution they act as preserving agents). The mixture is normally aged for one year.

Description of a perfume

musk deer It is impossible to describe a perfume according to its components because the exact formulas are kept secret. Even if the formulas are known, the ingredients are often too numerous to provide a useful classification. On the other hand, it is possible to group perfumes into olfactive families and describe them through the notes that appear as they slowly evaporate. Perfumes can also be classified according to their concentration.

Olfactive families

Traditionally, fragrances that are clasified in seven olfactive families, whose names may vary:
- Floral: Fragrances that are dominated by the scent of one or more types of flowers. When only one flower is used, it is called a soliflore (as in Dior's Diorissimo, with jasmine).
- Chypre: Fragrances build on a similar base consisting of bergamot, jasmine and oakmoss. This family of fragrances is named after a perfume by François Coty by the same name. Meaning Cyprus in French, the term alludes to where this base was inspired. This fragrance family is characterized by a scent reminiscent of apricot and custard.
- Fougère: Fragrances built on a base of lavender, coumarin and oakmoss. Many men's fragrances belong to this family of fragrances, which is characterized by its sharp herbaceous and woody scent.
- Leather: A family of fragrances which features the scents honey, tobacco, wood, and wood tars in its middle or base notes and a scent that alludes to leather.
- Woody: Fragrances that are dominated by the woody scents, typically of sandalwood and cedar. Patchouli, with in camphorous smell is also used in this fragrance family.
- Orientals or ambers: A large fragrance class featuring the scents of vanilla and animal scents together with flowers and woods. Typically enhanced by camphorous oils and incense resins, which bring to mind Victorian era imagery of the East and Far East.
- Citrus: An old fragrance family that until recently consisted mainly of "freshening" Eau de colognes due to the low tenacity of citrus scents. Development of newer fragrance compounds has allowed for the creation of primarily citrus fragrances.

Fragrance Notes

A mixture of alcohol and water is used as the solvent for the aromatics. On application, body heat causes the solvent to quickly disperse, leaving the fragrance to evaporate gradually over several hours. The rate of evaporation (vapor pressure) and the odor strength of the compound partly determine the tenaciousness of the compound and determine its perfume note classification.
- Top notes: Scents that are perceived a few minutes after the application of a perfume. Top notes create the scents that form a person's initial impression of a perfume. Because of this, they are very important in the selling of a perfume. The scents of this note class are usually described as "fresh," "assertive" or "sharp." The compounds that contribute to top notes are strong in scent, very volatile, and evaporate quickly. Citrus and ginger scents are common top notes.
- Heart notes or Middle notes: The scent of a perfume that emerges after the top notes dissipate. The heart note compounds form the "heart" or main body of a perfume and act to smooth the sharpness from the initial impression of a perfume caused by the top notes. Not surprisingly, the scent of heart note compounds is usually more mellow and "rounded." Scents from this note class appear anywhere from 10 minutes to 1 hour after the application of a perfume. Lavender and rose scents are typical heart notes.
- Base notes: The scent of a perfume that appears after the departure of the heart notes. Base notes bring depth and solidness to a perfume. Compounds of this class are usually the fixatives used to hold and boost the strength of the lighter top and heart notes. The compounds of this class of scents are typically rich and "deep" and are usually not perceived until 30 minutes after the application of the perfume or during the period of perfume dry-down. Musk, vetiver and scents of plant resins are commonly used as base notes.

Concentration

Perfumes oils, or the "juice" of a perfume composition, are diluted with a suitable solvent to make the perfume more usable. This is done because undiluted oils contain volatile components that would be too concentrated for people with sensitive skin or allergies. Although dilutions of the perfume oil can be done using solvents such as jojoba, fractionated coconut oil, and wax, the most common solvents for perfume oil dilution is ethanol or a mixture of ethanol and water. The percent of perfume oil by volume in a perfume is listed as follows:
- Perfume extract: 20%-40% aromatic compounds
- Eau de parfum: 10-30% aromatic compounds
- Eau de toilette: 5-20% aromatic compounds
- Eau de cologne: 2-3% aromatic compounds As the percentage of aromatic compounds decreases, the intensity and longevity of the scent decrease. It should be noted that different perfumeries or perfume houses assign different amounts of oils to each of their perfumes. As such, although the oil concentration of a perfume in eau de parfum dilution will necessarily be higher than the same perfume in eau de toilette form, the same trends may not necessarily apply to different perfume compositions much less across different perfume houses.

History of perfume and perfumery

ethanol Perfumery, or the art of making perfumes, began in ancient Egypt but was developed and further refined by the Romans and the Arabs. Knowledge of perfumery came to Europe as early as the 14th century. During the Renaissance period, perfumes were used primarily by royalty and the wealthy to mask bodily odors resulting from the sanitary practices of the day. In the Islamic culture, perfume usage has been documented as far back as the 6th century and its usage is considered a religious duty. The Prophet Muhammad said, "The taking of a bath on Friday is compulsory for every male Muslim who has attained the age of puberty and (also) the cleaning of his teeth with Siwak (type of twig used as a toothbrush), and the using of perfume if it is available." (Recorded in Sahih Bukhari) Partly due to this patronage, the western perfumery industry was created. By the 18th century, aromatic plants were being grown in the Grasse region of France to provide the growing perfume industry with raw materials. Even today, France remains the centre of the European perfume design and trade. Perfumers were also known to create poisons; for instance, a French duchess was murdered when a perfume/poison was rubbed into her gloves and was, thus, slowly absorbed into her skin.

Famous perfumes classified by year of creation

- 1714 : Eau de Cologne by Farina (Johann Maria Farina 1685-1766)
- 1889 : Jicky by Guerlain (Aimé Guerlain)
- 1917 : Chypre by François Coty (François Coty)
- 1919 : Mitsouko by Guerlain (Jacques Guerlain)
- 1919 : Tabac Blond by Caron (Ernest Daltroff)
- 1921 : N°5 by Chanel (Ernest Beaux)
- 1925 : Shalimar by Guerlain (Jacques Guerlain)
- 1927 : Arpège by Lanvin (André Fraysse)
- 1929 : Soir by Paris by Bourjois (Ernest Beaux)
- 1930 : Joy by Jean Patou (Henri Alméras)
- 1934 : Pour Un Homme by Caron (Ernest Daltroff)
- 1944 : Bandit by Robery Piguet (Germaine Cellier)
- 1945 : Femme by Rochas (Edmond Roudnitska)
- 1948 : L'Air du temps by Nina Ricci (Francis Fabron)
- 1956 : Diorissimo by Christian Dior (Edmond Roudnitska)
- 1959 : Monsieur by Givenchy
- 1959 : Cabochard by Parfums Grès (Bernard Chant)
- 1966 : Eau sauvage by Christian Dior (Edmond Roudnitska)
- 1969 : Ô by Lancôme (Robert Gonnon)
- 1977 : Opium by Yves Saint-Laurent (Jean-Louis Sieuzac)
- 1978 : Azzaro Pour Homme by Azzaro (Gérard Anthony, Martin Heiddenreich, Richard Wirtz)
- 1978 : Magie Noire by Lancôme (PFW)
- 1979 : Anaïs Anaïs by Cacharel (Roger Pellegrino)
- 1981 : Nombre Noir by Shiseido (Serge Lutens, Jean-Yves Leroy)
- 1983 : Paris by Yves Saint-Laurent (Sophia Grosjman)
- 1984 : Coco by Chanel (Jacques Polge)
- 1985 : Poison by Christian Dior (Jean Guichard)
- 1987 : Loulou by Cacharel (Jean Guichard)
- 1990 : Trésor by Lancôme (Sophia Grosjman)
- 1992 : Angel by Thierry Mugler (Olvier Cresp and Yves de Chiris)
- 1993 : Jean-Paul Gaultier by Jean-Paul Gaultier (Jacques Cavallier)
- 1995 : CK One by Calvin Klein (Firmenich)
- 1995 : Dolce Vita by Christian Dior (Pierre Bourdon and Maurice Roger)
- 1995 : Le Mâle by Jean-Paul Gaultier (Francis Kurkdjian)
- 2001 : Coco Mademoiselle by Chanel (Jacques Polge)
- 2001 : Nu by Yves Saint-Laurent (Jacques Cavallier)

Natural and synthetic aromatics

Plant sources

Plants have long been used in perfumery as a source of essential oils and aroma compounds. These aromatics are usually secondary metabolites produced by plants as protection against herbivores as well as to attract pollinators. Plants are by far the largest source of fragrant compounds used in perfumery. The sources of these compounds may be derived from various parts of a plant. A plant can offer more than one source of aromatics, for instance the aerial portions and seeds of coriander have remarkably different odors from each other. Orange leaves, blossoms, and fruit zest are the respective sources of petit grain, neroli, and orange oils.
- Flowers and Blossoms: Undoubtably the largest source of aromatics. Includes the flowers of several species of rose and lavender, as well as jasmine, osmanthus, mimosa, tuberose, as well as the blossoms of citrus and ylang-ylang trees. Although not traditionally thought of as a flower, the unopened flower buds of the clove are also commonly used. Orchid flowers are not commercially used to produce essential oils or absolutes.
- Leaves and Twigs: Commonly used for perfumery are patchouli, sage, violets, rosemary, and citrus leaves. Sometimes leaves are valued for the "green" smell they bring to perfumes, examples of this include hay and tomato leaf.
- Roots, rhizomes and bulbs: Commonly used terrestrial portions in perfumery include iris rhizomes, vetiver roots, various rhizomes of the ginger family.
- Seeds: Commonly used seeds include tonka bean, coriander, caraway, cocoa, nutmeg, mace, cardamom, and anise.
- Fruits: Fresh fruits such as apples, strawberries, cherries unfortunately do not yield the expected odors; if you find such fragrance notes in a perfume, they're synthetic. Notable exceptions include litsea cubeba, vanilla, and juniper berry. The most commonly used fruits yield their aromatics from the rind; they include citrus such as oranges, lemons, limes, and grapefruit.
- Woods: Highly important in providing the base notes to a perfume, wood oils and distillates are indispensible in perfumery. Commonly used woods include sandalwood, rosewood, agarwood, birch, cedar, juniper, and pine.
- Bark: Commonly used barks includes cinnamon and cascarilla. The fragrant oil in sassafras root bark is also used either directly or purified for its main constituent, safrole, which is used in the synthesis of other fragrant compounds such as helional.
- Resins: Valued since antiquity, resins have been widely used in incense and perfumery. Highly fragrant and antiseptic resins and resin-containing perfumes have been used by many cultures as medicines for a large variety of ailments. Commonly used resins in perfumery include labdanum, frankincense/olibanum, myrrh, Peru balsam, gum benzoin. Pine and fir resins are a particularly valued source of terpenes used in the organic synthesis of many other synthetic or naturally occurring aromatic compounds. Some of what is called amber and copal in perfumery today is the resinous secretion of fossil conifers.
- Lichens: Commonly used lichen includes oakmoss and treemoss thalli.

Animal sources

- Musk: Originally derived from the musk sacs from the Asian musk deer, it has now been replaced by the use of synthetic musks due to its price and various ethical issues.
- Civet: Also call Civet Musk, this is obtained from the odorous sacs of the civets, animals in the family Viverridae, related to the Mongoose.
- Castoreum: Obtained from the odorous sacs of the North American beaver.
- Ambergris: Lumps of oxidized fatty compounds, whose precursors were secreted and expelled by the Sperm Whale. Ambergris is commonly referred as "amber" in perfumery and should not be confused with yellow amber, which is used in jewelry.
- Honeycomb: Distilled from the honeycomb of the Honeybee.

Synthetic sources

Synthetic aromatics are created through organic synthesis from various chemical compounds that are obtained from petroleum distillates, pine resins, or other relatively cheap organic feedstock. Synthetics can provide fragrances which are not found in nature. For instance, Calone, a compound of synthetic origin, imparts a fresh ozonous metallic marine scent that is widely used in contemporary perfumes. Synthetic aromatics are often used as an alternate source of compounds that are not easily obtained from natural sources. For example, linalool and coumarin are both naturally occurring compounds that can be cheaply synthesized from terpenes. Orchid scents are usually not obtained directly from the plant itself but are instead synthetically created to match the fragrant compounds found in various orchids. The majority of the world's synthetic aromatics are created by relatively few companies. They include:
- International Flavors and Fragrances (IFF)
- Givaudan-Roure
- Firmenich
- Quest International
- Takasago
- Symrise Each of these companies patent several processes for the production of aromatic synthetics annually. See Aroma compound

Health and ethical issues

Use of Aromatics

In some cases, an excessive use of perfumes may cause allergic reactions of the skin. For instance, acetophenone, ethyl acetate and acetone while present in many perfumes, are also known or potential respiratory allergens. It is important to note that there is no benefit from creating a perfume exclusively from natural materials. There are several reasons for this:
- Many natural aroma materials are in fact inherently toxic and are either banned or restricted by IFRA. These naturals have been replaced by safer artificial or synthetic materials.
- Many natural materials and essential oil contain the same chemicals used in perfumes that are classified as allergens, many of them at higher concentrations.
- Perfume composed only of expensive natural materials could be very expensive. Synthetic aromatics make possible perfumes at reasonable prices.
- In the distillation of natural essential oils any biocides (including pesticides, herbicides, or fungicides) that have been applied while the plant is growing may be concentrated into the essential oil making the oil toxic. Unless the essential oil is distilled from a certified organic origin, it may be dangerous.
- There are many new synthetic aromas that bear no olfactory relationship to any natural material and yet modern perfumery depends on these new odours for the infinite variety of perfumes available today. Many synthetics have very beautiful aromas not available in nature.

Natural Musk

Musk was traditionally taken from the male musk deer Moschus moschiferus. This requires the killing of the animal in the process. Although the musk pod is produced only by a young male deer in oestrus musk hunters usually did not discriminate between the age and sex of the deers. Due to the high demand of musk and indiscriminate hunting, populations were severely depleted. As a result, the deer is now protected by law and international trade of musk from Moschus moschiferus is prohibited:

"Musk deer are protected under national legislation in many countries where they are found. The musk deer populations of Afghanistan, Bhutan, India, Nepal and Pakistan are included in Appendix I of CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora. This means that these musk deer and their derivatives are banned from international commercial trade." [http://www.traffic.org/factfile/factfile_muskdeer.html]

Due to its legality, rarity, high price, and ethical reasons, it is the policy of many perfume companies to use synthetic musk in place of natural musk for ethical reasons. Numerous synthetic musks of high quality are readily available. [http://www.ifraorg.org/GuideLines.asp approved safe by IFRA].

External links

- [http://www.biblioparfum.net Biblioparfum] An impressive personal collection of more than 600 books about perfume (mostly French)
- [http://www.fabulousfragrances.com Fabulous Fragrances] An educational perfume portal with information on perfume usage, fragrance classifications, and history. Includes books by Jan Moran (Fabulous Fragrances II) and Michael Edwards (Fragrances of the World), as well as online programs, a forum, and a Q & A column, Scents of Style, where readers can ask questions.
- [http://hjem.get2net.dk/bojensen/EssentialOilsEng/EssentialOils.htm A guide to natural fragrances] A site with information regarding various fragrant plants used in perfumery and their active chemical odorants. Images of both plant and odorant structure.
- [http://www.schoolscience.co.uk/content/5/chemistry/smells/index.html The sense of smell.] Educational site with information regarding the sense of smell, the process of fragrance evaluation, and a bit on organic synthesis of fragrance chemicals.
- [http://www.osmoz.com/index_menu.asp osMoz] Overview of the perfume and cologne making process, fragrance classifications, and a directory of leading perfumers.
- [http://www.leffingwell.com/perfume.htm Leffingwell & Associates] An independent consulting agency on fragrance and flavour chemicals Category:Perfumery Category:Olfaction ja:香水

Analytical chemistry

Analytical chemistry is the analysis of material samples to gain an understanding of their chemical composition and structure.

Types

Analytical chemistry can be split into two main types, qualitative and quantitative: #Qualitative inorganic analysis seeks to establish the presence of a given element or inorganic compound in a sample. #Qualitative organic analysis seeks to establish the presence of a given functional group or organic compound in a sample. #Quantitative analysis seeks to establish the amount of a given element or compound in a sample. Most modern analytical chemistry is quantitative. Quantitative analysis can be further split into different areas of study. The material can be analyzed for the amount of an element or for the amount of an element in a specific chemical species. The latter is of particular interest in biological systems; the molecules of life contain carbon, hydrogen, oxygen, nitrogen, and others, in many complex structures.

Techniques

There are a bewildering array of techniques available to separate, detect and measure chemical compounds.
- Separation of chemicals in order to measure the weight or volume of a final product. This is an older process and can be quite painstaking, but is an essential first step when dealing with certain mixtures of substances, like extracts from organisms. Modern separation techniques such as HPLC often seek to separate and determine amount or identity in a single automated analysis by integrating a detector.
- Titration is a technique used to determine amounts present in solution or a physical characteristic of a molecule such as an equilibrium constant.
- Analysis of substances with devices using spectroscopy. By measuring the absorption or emission of light, or other types of radiation, by a substance we can calculate the amounts of species or characterize the chemical species, often without separation. Newer methods include atomic absorption spectroscopy (AAS), nuclear magnetic resonance (NMR) and neutron activation analysis (NAA).
- Mass spectrometry is used to determine the molecular mass, the elemental composition, structure and sometimes amount of chemical species in a sample by ionizing the analyte molecules and observing their behavior in electric and magnet