238 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS appeared to inhibit these enzymes, and magnesium or manganese to activate them.69 Mutation was induced at 1,000 times the natural rate by addition of 5-bromouracil and sulphanilamide to virus culture media. 7ø Strong evidence has been presented that human cells do not contain 48 chromosomes, as so long believed, but 46. 7• PROTEIN BIOSYNTHESIS Protein synthesis was observed in isolated cell nuclei from calf thymus, the participation of deoxyribonucleic acid being essential, and the high energy requirements being supplied by intranuclear systems which generate energy-rich triphosphates. 72 A specific surface and available energy were found indispensable for formation and orientation of peptide chains, and high-pressure resynthesis of proteins in the presence of proteolytic enzymes disproved the need of different specific catalysts for each peptide bond. TM New models and hypotheses were offered to explain the transfer of specificity from the deoxyribonucleic acid of the gene, through the specific ribonucleic acid, to the enzymes being synthesised, •4,75 and additional statistical evidence was offered to support an earlier hypothesis that the 20 amino- acids found in proteins are disposed in the new protein molecule to match the 20 possible triplets of nucleotide residues which can be formed from four different nucleotides, disregarding order. TM A chemical manufacturer announced the opening of a pilot plant which will be capable of producing all the essential amino acids except threonine. 77 PROTEIN STRUCTURE The complete amino-acid sequence of alpha-corticotropin was estab- blished, 79 as was that of beta-corticotropin 7• the latter contains 39 amino acids in its chain, but a 24-unit portion of the chain retains the hormonal activity. A new model was proposed for feather keratin, with 64 amino-acid residues in the 190A unit of pitch, and ten helixes coaxially aggregated by lateral H-bonds. TM It was shown that a • primary valence bond in a protein may have more apparent stability than the corresponding bond in a low molecular weight compound becaase of support by neighbottring H-bonds, which may account for some observed differences in the behaviour of pro- teolytic enzymes toward native and denatured protein substrates. • A new method was devised for measuring distances between protein sidechains, based on the absorption spectra of their compounds with molecules contain- ing two groups separated by known distances and capable of binding the two protein sidechains.•2 Melanin, keratin, and collagen formed crystalline substances'under mild influences such as ultrasonic waves, hydrogen peroxide, or various diseased

SOME NEW KEYS TO COSMETIC CHEMISTRY--19$6 239 conditions. sa Denaturation was considered to involve extensive disturbance of weak bonds formed by the side chains, without alteration of many intra- chain bonds. 8• The conditions for the helix-to-random-coil transition in- volved in denaturation were more narrowly defined, and methods were devised for inducing the controlled degradation of nucleic acid necessary for study of its structure. 85 Ribonucleic acid 8ø and deoxyribonucleic acid" were synthesised, albeit by enzymatic methods which shed little light on the structure. A theory was advanced to explain elastic mechanisms in fibrous proteins on the basis of melting of their crystalline regions, 88 such melting possibly occurring as the result of an agent which combines more readily with the liquid protein, thus shifting the equilibrium.89 COLLAGEN AND ELASTIN Recent books bearing upon collagen include Fibrous Proteir•s arid Their Biological Significance, 9 o originating in the Society for Experimental Biology, and The Chemistry arid Reactivity of Collagen 9•. by K. H. Gustarson. Numer- ous investigators have contributed to the cracking of the tough problem of collagen structure, but a working model acceptable to all parties is still lacking. There seems to be general agreement92, 9• that collagen possesses a three-chain coiled-coil structure with right-handed major and left-handed minor helix, 9•,95 with individual chains ending at staggered positions. The chains are most probably of the poly-L-proline type, and may not all have the same amino-acid sequence. 96," Acid-stable cross links of at least two varieties are present in varying degree in different collagens. 98 Two 'typical building-stones of collagen, delta-hydroxylysine and 4-hydroxyproline, have attracted considerable study, since each has 16 possible stereoisomers.•9, • 0o A study using glycine-C TM led to the conclusion that albumins are the pre- decessors of skin collagens. TM X-ray studies under small incidence angles indicated that the cross striations of collagen are not results of the protein structure, but are caused by polysaccharides held to the protein chains by forces weaker than covalent bonds. •ø2 Collagens from different tissues showed varied degrees of resistance to cleavag• because of different surface films or coatings. •øa Chlorinated naphthalene, which produced hyper- keratosis in calves, also depressed plasma levels of vitamin A and ascorbic acid suggesting that the pathological changes in skin and connective 'iissues might be connected with those substances. TM The arnino-acid composition of elastoidin from the ceratotrichia of a shark justified its inclusion in the collagen group of proteins, but its high tyrosine and cystine content were cited as the possible basis of it• peculiar hydrothermal behaviour. •ø• Collagen treated with enzymes, acids, or alkalis formed networks of fibres resembling elastin.•ø•, •ø• Rats fed a diet containing 50 per cent Lathyrus odoratus meal developed aneurysms of the aorta, as a result of general lysis of elastic fibres. • o8