抄録
In order to clarify why silk is so rapidly colored by light, and why irradiated silk becomes difficult to solve in its solvents such as cupriethylenediamine, some peptides separated from its hydrolyzate were studied.
It was recognized that some of the peptides separated on the filter paper of chromatogram were colored to brown, one of them was colored to bright yellow, and others remained unchanged, when they were irradiated by sunlight or a fade-o-meter. “Browning” of silk is, therefore, a hybrid of above-mentioned changes. Some of unchanged peptides contain tyrosine in their component, though it is believed that this amino acid is the most influential cause of the browning. The peptide turned to bright yellow by sunlight is the only one which contains tryptophan. The browned peptides have something in common in the respect of containing tyrosine and glutamic acid in company.
Two abnornal peptides were separated from the hydrolyzate of the insoluble part of irradiated silk. One of them contains much of dopa (dihydroxyphenylalanine) and a little of glycine and glutamic acid. Another peptide contains serine, arginine, alanine and glycine. It is interesting to note that dopa accumulates in this part, though its presence in irradiated silk is already known.
Some discussion is offered with the suggestion that the insolubilization of irradiated silk might be-caused by cross-linking between dopa or serine residues of confronting polypeptide chains.
