m Flavor Chemistry of Animal Foods ACS Symposium Series No. 67 Roger W. Bullard, Editor U.S. Fish and Wildlife Service A symposium sponsored by the Division of Agricultural and Food Chemistry of the American Chemical Society. The recent revolution in animal foods has produced high quality, more palatable foods for domestic pets and foodproducing animals. Now research is also being directed toward meeting the needs of threatened wildlife species as well as toward controlling their destruction of human food supplies. Since animals cannot directly appraise food or food additives, there are many unique problems in animal flavor research that require the cooperation from specialists in many different fields. This volume covers the problems and recent advances in this field. Many domestic and non-domestic animals are discussed by specialists in organic and analytical chemistry, biochemistry, behavior, biology, nutrition, and physiology. CONTENTS Animal Flavor Research · Food Preference Behavior · Methodology of Behavioral Testing • Chemical Fractions from Estrus Urine · Bacterial Action and Chemical Signalling · Taste and Smell · Carnivore Taste Systems · Diets for Food-Producing Animals · Palatable Foods for Domestic Pets · Repellents to Protect Crops 175 pages (1978) clothbound $19.00 LC 77-27295 ISBN 0-8412-0404-7
SIS/American Chemical Society 1155 16th St., N.W./Wash., D.C. 20036 Please send copies of SS 67 Flavor Chemistry of Animal Foods at $19.00 per copy. G Check enclosed for $ D Bill me. Postpaid in U.S. and Canada, plus 75 cents elsewhere. Name Address City
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C&EN March 27, 1978
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Photomicrograph shows filaments on surface of cell containing epiglycanin
That glycoprotein contains more than 500 carbohydrate chains per molecule of protein. And in all, it accounts for more than half of the sialic acid on the tumor cell surface, according to Codington. The protein's molecular weight is 500,000. Codington emphasizes that no evidence yet puts epiglycaninlike molecules on human cancer cells. However, such phenomena may have relevance, particularly to the occurrence of metastases (secondary tumors), in human disease. D
New uses for soluble polymers explored
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Although use of polymers in organic syntheses dates back 15 years, the strategies are shifting and the practice is growing. Dr. Manfred Mutter outlined the progress that he, Dr. Ernst Bayer, and their colleagues at the University of Tubingen in West Germany are making in applying soluble polymers to various technical problems. Principal among their efforts, Mutter told the Division of Organic Chemistry, is organic synthesis. However, soluble polymer "complexing" agents also are being developed to remove toxic metals from wastewaters or radioactive metals from nuclear waste fluids. The biggest boost for polymers in synthetic applications comes from working with soluble polymers, Mutter notes. They overcome the disadvantages of solid-phase polymers, such as steric hindrance and poor solvation, and provide advantages such as easy separation of products and higher yields. Polyethylene glycol (and derivatives) is the most versatile of soluble polymers, according to Mutter. The polymer is very soluble in most solvents, but can be crystallized during separation steps to remove
low-molecular-weight material. Also, most functional groups on the polymer are equally accessible to the solvent assuring their uniform reactivity. "Reaction rates do not differ from the corresponding low-molecular-weight reactions," Mutter says. Thus, the reactions go "in analogy" to low-molecular-weight—that is, standard—systems. The high solubility of polyethylene glycol offers a decided advantage in peptide synthesis, Mutter notes. Building up such strings of amino acids can be hampered by the peptide's poor solubility during ordinary liquid phase procedures. But the "strong solubilizing power" of polyethylene glycol helps overcome that problem, forcing the growing peptides to stay in solution. There are several tricks for removing unused reagents from the polymer, according to Mutter. For example, the polymer can be crystallized from solution, and the excess reagents washed away. Another strategy is to pump the solution through a semipermeable membrane, retaining the polymer but passing the excess reagents. Yet another more familiar use is solvent extraction. The West German group is studying use of polymers in another important problem area, the removal of metals from wastewater. They are developing methods based on "soluble polymer complexing agents, which selectively bind certain metal ions," Tubingen's Bayer tells C&EN. Because the reaction takes place in homogeneous solutions—again, soluble polymers are used—"it is much faster than ion exchange." Several polymers have been synthesized that are equipped with various chelating groups to bind metals, Bayer notes. For example, polymers such as polyethyleneimine, polyvinyl sulfonic acid, and polyacrylic acid with chelating groups such as thiourea, 8-hydroxyquinoline, iminodiacetic acid, and hydroxyaniline are being tried. Thus, for instance, polyethyleneimine containing "thiouronium" (from thiourea) binds 1 gram of mercury per gram of polymer. This capacity is "especially high," according to Bayer, and the polymer system removes 99.9% of mercury (present in a range of 1 to 100 ppb) in two passes through a semipermeable membrane. "The procedure is at least as feasible as that most frequently used—reduction with hydrazine and adsorption of mercury on activated charcoal," Bayer says. An added advantage of the polymer technique is that the mercury is recoverable by electrolysis whereas the charcoaladsorbed mercury usually is dumped. Another polymer, based on acrylic acid, looks promising for plutonium recovery, Bayer says. It is highly selective for plutonium, removing the metal with up to 99.7% efficiency from mixes of radioactive wastes. It also works efficiently under weakly acidic conditions and with tributyl phosphate present. These high efficiencies might offer "new horizons" for plutonium removal problems at atomic power plants, he notes. D
