Abstract
The oxidation of silk fibroin by potassium permanganate has been studied, and from this intermediate oxidative substances four fractions were obtained by the authors, Fraction IV was acidic peptide and consisted of glycine, alanine, valine and leucine.
Therefore fraction IV was examined exclusively in this report. This fraction shows acidic and requires 0.1n-NaOH 15.70cc to be neutral. Oxalic acid was separated excepting amino acids from the hydrolysate of this fraction and determined.
From these results, it was recognized that at the terminal of this peptide existed oxalyl residue. Therefore, the structural formula of this peptide was considered as follows:
COON-CH-R1-NH-CO-CH-R2-NH----CO-CH-Rn-NH-CO-COOH
There is no description of this peptide, hence the authors named it “oxalyl peptide”.
It was recognized that the hydrolysate of this fraction included serine, arginine and lysine excepting the above-mentioned four amino acids.
This fraction has been investigated by means of paper chromatography, dialysis, paper ionophoresis and spectrophotometry and from these results it was recognized that this fraction was the mixture consisted of “oxalyl peptide” mainly and other several peptides.
By paper chromatography of the hydrolysate of DNP-fraction IV, the latter was recognized four kinds of peptides having glycine, alanine, serine and arginine respectively as α-amino terminal residues.
