THE EMERGING COSMETIC INDUSTRY 31 contain several thousand different enzymes, each of which promotes a chemi- cal reaction. Lansing and Rosenthal" reached the conclusion that ribonuc- leic acid at the cell surface is involved in the transfer of substances across the cell surface. Promotion of various chemical reactions has been localised in definite cell structures," ,8 and Bracket" has summarised evidence that the nucleus is not the centre of all protein synthesis, although it may control many of the biochemical processes in the cell through its role in nucleotide synthesis. Kopac 2o recently described a micromanipulator used under an ultra-violet microscope, with images made visible through a closed television chain, which allowed sub-cellular particulates to be transplanted to a non- aqueous fluid and observed there. Kirk • reported that instruments he is now developing show promise of being about one hundred times as sensitive as those now in use, and of making possible accurate analyses of single living cells. ENZYME MECHANISMS Since so many biochemical processes depend on the participation of one or more enzymes for their effective functioning, an understanding of enzyme action must be included in our cosmetic chemistry. It has been fairly well established that enzymes, as well as many other catalysts, depend for their activity upon a portion of their surface which contains polar groups in an arrangement closely matching polar groups of the opposite charge in the substrate molecule. 22 The substrate is thereby held closely upon the enzyme, and has its charges so shifted that it is more reactive than a free molecule of the same kind. Leach and Lindley,* reported that a number of enzymes which had been subjected to amino acid analysis showed higher contents of polar residues than did non-enzymic proteins, implying that the enzymes possessed many carboxyl-hydroxyl interchain hydrogen bonds, forming a highly resonating network. Klotz and Loh Ming 04 clarified the role of certain metals as promoters of enzyme reactions by showing that the metals form bridges between enzymes and various organic molecules. Koshland" pre- sented evidence that enzyme mechanisms are analogous to those of simpler catalysts, and held out hope for early elucidation of the nature and behaviour of the active groups on protein surfaces. PROTEIN STRUCTURE AND FORMATION The composition and properties of one protein, keratin, have attracted the interest and study of cosmetic chemists for some years, but there remain many gaps in our knowledge of this and other proteins. Techniques of amino acid analysis have improved to the point where most of these units can be recovered within 3 per cent of theory by means of chromatography on a 4 per cent cross-linked polystyrene resin. 2'

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