期刊名称：LIPIDS ISSN： 0024-4201 版本： SCI-CDE 出版频率： Monthly 出版社： WILEY, 111 RIVER ST, HOBOKEN, USA, NJ, 07030-5774   出版社网址： http://www.springer.com/?SGWID=8-102-0-0-0 期刊网址： http://www.springer.com/life+sciences/journal/11745 影响因子： 1.88 主题范畴： BIOCHEMISTRY & MOLECULAR BIOLOGY;    NUTRITION & DIETETICS 期刊简介(About the journal)    投稿须知(Instructions to Authors)    编辑部信息(Editorial Board)    About the journal Lipids was introduced in 1966 and is one of the premier journals published in the lipid field today. This monthly journal features full-length original research articles, short communications, methods papers, and review articles on timely topics. All papers are meticulously peer-reviewed and edited by some of the foremost experts in their respective fields. About the journal 0024-4201.pdf Instructions to Authors 1. Fatty Acids The common feature of these lipids is that they are all esters of moderate to long chain fatty acids. Acid or base-cayalyzed hydrolysis yields the component fatty acid, some examples of which are given in the following table, together with the alcohol component of the lipid. These long-chain carboxylic acids are generally referred to by their common names, which in most cases reflect their sources. Natural fatty acids may be saturated or unsaturated, and as the following data indicate, the saturated acids have higher melting points than unsaturated acids of corresponding size. The double bonds in the unsaturated compounds listed on the right are all cis (or Z). FATTY ACIDS Saturated Formula Common Name Melting Point CH3(CH2)10CO2H lauric acid 45 ºC CH3(CH2)12CO2H myristic acid 55 ºC CH3(CH2)14CO2H palmitic acid 63 ºC CH3(CH2)16CO2H stearic acid 69 ºC CH3(CH2)18CO2H arachidic acid 76 ºC Unsaturated Formula Common Name Melting Point CH3(CH2)5CH=CH(CH2)7CO2H palmitoleic acid 0 ºC CH3(CH2)7CH=CH(CH2)7CO2H oleic acid 13 ºC CH3(CH2)4CH=CHCH2CH=CH(CH2)7CO2H linoleic acid -5 ºC CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7CO2H linolenic acid -11 ºC CH3(CH2)4(CH=CHCH2)4(CH2)2CO2H arachidonic acid -49 ºC The higher melting points of the saturated fatty acids reflect the uniform rod-like shape of their molecules. The cis-double bond(s) in the unsaturated fatty acids introduce a kink in their shape, which makes it more difficut to pack their molecules together in a stable repeating array or crystalline lattice. The trans-double bond isomer of oleic acid, known as elaidic acid, has a linear shape and a melting point of 45 ºC (32 ºC higher than its cis isomer). The shapes of stearic and oleic acids are displayed in the models below. You may examine Chime models of these compounds by clicking on the desired model picture. stearic acid oleic acid Two polyunsaturated fatty acids, linoleic and linolenic, are designated "essential" because their absence in the human diet has been associated with health problems, such as scaley skin, stunted growth and increased dehydration. These acids are also precursors to the prostaglandins, a family of physiologically potent lipids present in minute amounts in most body tissues. Because of their enhanced acidity, carboxylic acids react with bases to form ionic salts, as shown in the following equations. In the case of alkali metal hydroxides and simple amines (or ammonia) the resulting salts have pronounced ionic character and are usually soluble in water. Heavy metals such as silver, mercury and lead form salts having more covalent character (3rd example), and the water solubility is reduced, especially for acids composed of four or more carbon atoms. RCO2H + NaHCO3 RCO2(¨C) Na(+)   +   CO2   +   H2O RCO2H + (CH3)3N: RCO2(¨C) (CH3)3NH(+) RCO2H + AgOH RCO2¦Ä(¨C) Ag¦Ä(+)   +   H2O Unusual Fatty Acids Nature has constructed a remarkable variety of fatty acid derivatives. To see some of these compounds Click Here. 2. Soaps and Detergents Carboxylic acids and salts having alkyl chains longer than eight carbons exhibit unusual behavior in water due to the presence of both hydrophilic (CO2) and hydrophobic (alkyl) regions in the same molecule. Such molecules are termed amphiphilic (Gk. amphi = both) or amphipathic. Fatty acids made up of ten or more carbon atoms are nearly insoluble in water, and because of their lower density, float on the surface when mixed with water. Unlike paraffin or other alkanes, which tend to puddle on the waters surface, these fatty acids spread evenly over an extended water surface, eventially forming a monomolecular layer in which the polar carboxyl groups are hydrogen bonded at the water interface, and the hydrocarbon chains are aligned together away from the water. This behavior is illustrated in the diagram on the right. Substances that accumulate at water surfaces and change the surface properties are called surfactants. Alkali metal salts of fatty acids are more soluble in water than the acids themselves, and the amphiphilic character of these substances also make them strong surfactants. The most common examples of such compounds are soaps and detergents, four of which are shown below. Note that each of these molecules has a nonpolar hydrocarbon chain, the "tail", and a polar (often ionic) "head group". The use of such compounds as cleaning agents is facilitated by their surfactant character, which lowers the surface tension of water, allowing it to penetrate and wet a variety of materials. Very small amounts of these surfactants dissolve in water to give a random dispersion of solute molecules. However, when the concentration is increased an interesting change occurs. The surfactant molecules reversibly assemble into polymolecular aggregates called micelles. By gathering the hydrophobic chains together in the center of the micelle, disruption of the hydrogen bonded structure of liquid water is minimized, and the polar head groups extend into the surrounding water where they participate in hydrogen bonding. These micelles are often spherical in shape, but may also assume cylindrical and branched forms, as illustrated on the right. Here the polar head group is designated by a blue circle, and the nonpolar tail is a zig-zag black line. An animated display of micelle formation is presented below. Notice the brownish material in the center of the three-dimensional drawing on the left. This illustrates a second important factor contributing to the use of these amphiphiles as cleaning agents. Micelles are able to encapsulate nonpolar substances such as grease within their hydrophobic center, and thus solubilize it so it is removed with the wash water. Since the micelles of anionic amphiphiles have a negatively charged surface, they repel one another and the nonpolar dirt is effectively emulsified. To summarize, the presence of a soap or a detergent in water facilitates the wetting of all parts of the object to be cleaned, and removes water-insoluble dirt by incorporation in micelles. If the animation has stopped, it may be restarted by clicking on it. The oldest amphiphilic cleaning agent known to humans is soap. Soap is manufactured by the base-catalyzed hydrolysis (saponification) of animal fat (see below). Before sodium hydroxide was commercially available, a boiling solution of potassium carbonate leached from wood ashes was used. Soft potassium soaps were then converted to the harder sodium soaps by washing with salt solution. The importance of soap to human civilization is documented by history, but some problems associated with its use have been recognized. One of these is caused by the weak acidity (pKa ca. 4.9) of the fatty acids. Solutions of alkali metal soaps are slightly alkaline (pH 8 to 9) due to hydrolysis. If the pH of a soap solution is lowered by acidic contaminants, insoluble fatty acids precipitate and form a scum. A second problem is caused by the presence of calcium and magnesium salts in the water supply (hard water). These divalent cations cause aggregation of the micelles, which then deposit as a dirty scum. These problems have been alleviated by the development of synthetic amphiphiles called detergents (or syndets). By using a much stronger acid for the polar head group, water solutions of the amphiphile are less sensitive to pH changes. Also the sulfonate functions used for virtually all anionic detergents confer greater solubility on micelles incorporating the alkaline earth cations found in hard water. Variations on the amphiphile theme have led to the development of other classes, such as the cationic and nonionic detergents shown above. Cationic detergents often exhibit germicidal properties, and their ability to change surface pH has made them useful as fabric softners and hair conditioners. These versatile chemical "tools" have dramatically transformed the household and personal care cleaning product markets over the past fifty years. Editorial Board Lipids Editor-in-Chief: Howard R. Knapp Associate Editors Robert G. Ackman Richard O. Adlof Alan R. Brash Pamela J. Fraker William McLean Grogan James A. Hamilton Lloyd A. Horrocks David Y. Hui Laura J. Jenski Darshan S. Kelley John K.G. Kramer Arnis Kuksis Suzanne G. Laychock Robert A. Moreau Eric J. Murphy John J. Murray Etsuo Niki Ernst H. Oliw Robert E. Pitas Colin Ratledge Norman Salem Friedhelm Schroeder Andrew J. Sinclair Larry L. Swift Maret G. Traber Clemens von Schacky Production Editor: Pam Landman Editorial Advisory Board Members A. Richard Baldwin Wolfgang J. Baumann David J. Chitwood William W. Christie William J. Elliot Harold W. Gardner Frank D. Gunstone Mats Hamberg Sven Hammarström William S. Harris Raymond J. Hohl Ralph T. Holman David Kritchevsky Marcel S.F. Lie Ken Jie Burton J. Litman Helmut K. Mangold Gary Nelson David E. Ong Forrest Quackenbush Angelo M. Scanu Hannsjörg W. Seyberth Leland L. Smith Fred L. Snyder Howard W. Sprecher Phyllis J. Stumbo Paul K. Stumpf