32 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Protein Biogenesis. Radioactive isotopes have aided immensely in the study of how new protein molecules are formed. An attractive hypothesis calls for the binding of amino acids or small polypeptides to the parent molecule, each unit in the protein attracting its duplicate from the nutrient fluid, so that all the units so assembled can then join together to torm a new protein molecule which is an exact copy of the parent. Neugebauer 27 made the quantum-mechanical calculations necessary to show that the energy released by the Van der Waals binding of amino acids to a protein is sufficient to dissolve single chemical bonds, thus allowing the amino acid units to join into a protein chain. Neugebauer marshalled considerable evidence for the belief that multiplication of chromosomes, viruses, enzymes, etc., proceeds by this mechanism. Zamecnik and Keller 28 succeeded in incorporating amino acids into protein in a cell-free system, finding the highest rate of synthesis in the microsome- rich fraction. Spiegelman • concluded from study of enzyme formation in yeast and bacteria that enzyme protein is formed primarily from free amino acids without intermediate peptide formation, and that the various amino acids are utilised simultaneously, not stepwise. Cohn •ø found that/•-galac- tosidase of Escherichia coli did not exchange amino acids with other proteins of its external medium, and raised the question whether the turnover of proteins in mammals does not indicate an actual turnover of tissues, i.e. the death of some cells and the use of their degradation products by new cells a question of great interest to cosmetic chemists. In studies on regenerating rabbit skin, Lipkan and Kerova*• obtained evidence that deoxyribonucleic acid plays a definite part in protein biosynthesis. PROTEIN STRUCTURE Astbury -'• and Pauling and Corey 8' were largely responsible for assembling X-ray diffraction data which established the bond lengths and angles, steric hindrances and hydrogen bonding in polypeptide chains from their work fairly definite concepts of possible structures for some of the fibrous proteins have been formulated. Harker 8• recently predicted that mathematical analysis of Patterson projections of X-ray diffraction patterns will within the next few years yield a detailed knowledge of the atomic arrangement in crystalline proteins. l•leanwhile, many complex polypeptides have been broken down by •elective enzymic hydrolysis so that the numbers and sequence of their amino acid residues are now known. ** On the other hand, polypeptides of lower molecular weight have been synthesised, an outstanding example being du Vigneaud's" synthesis of the pituitary hormone, oxytocin. Holley

THE EMERGING COSMETIC INDUSTRY 33 and Sondheimer" recently reported new methods of protecting side chains of the more sensitive amino acids, which are expected to facilitate the synthesis of much larger polypeptides. The advances made in the past few years toward understanding the structure and biosynthesis of proteins indicate clearly that cosmetic chemists will soon have a much timer basis for their concepts of skin biochemistry. ALLERGIC PHENOMENA A weighty problem for every cosmetic chemist is that of avoiding the use of ingredients or combinations which may produce untoward effects on significant numbers of users. Since the chemical basis of allergic action is not known, it is now necessary to test any new ingredient by lengthy, cum- bersome, and expensive pharmacological methods. Recently, some progress has been made in investigation of allergy on a chemical level. Krasovskaya 38 reported that in processes of sensitisation, the respiratory function of guinea pig leucocytes is lowered, as evidenced by decrease in oxidase granules. It is fairly well established that allergens combine with proteins of the tissues, and that the formation of antibodies to these protein- allergen compounds is an essential feature of allergic reaction to small molecules. Frcde•icq •9 determined the affinities of a larger number of aromatic compounds for bovine plasma albumin, and found that the affinity rises with increase in the number of benzene rings and is increased by hydroxyl or nitro groups, and by halogen atoms. Names of rather vague significance, such as hapten, antigen, antibody, may be defined in chemical and physical terms if work such as that of Pressman can be extended. Pressman 40 studied the specific precipitation of antibodies formed against benzoate ions, and determined the relative inhibitions of this precipitation produced by various chloro-substituted phenylazobenzoates. He was thus able to obtain information on closeness of fit of antibody about hapten. He found4• that substituents ortho to the carboxyl group decrease free energy of interaction, probably by twisting the carboxylate ion out of the plane of the benzene ring. Singer" obtained thermodynamic data which led him to conclude that there is a single carboxyl group in each antigert-antibody bond which must be ionised for the bond to form. STRUCTURE AND PHYSIOLOGICAL ACTIVITY For many decades chemists have striven to deduce generalisations con- necting chemical structure with physiological effect. Cosmetic chemists encounter the problem in such diverse aspects as the correlation of odour and structure, and the avoidance of irritating ingredients. A landmark appears