Introduction of new crosslinks into proteins

Abstract

Analysis of the crosslinks epsilon-(gamma-glutamyl) lysine and epsilon- (beta-aspartyl) lysine present in treated wool has been improved by modifying the enzymic digestion. Treatment of wool with either monocarboxylic acid chlorides in dimethylsulfoxide or with 1-fluoro-2,4-dinitrobenzene in the presence of acetate considerably decreased epsilon-amino groups and solubility. Since no information of interchain amide crosslinks was observed, the hypothesis of so-called self-crosslinking postulated by ZAHN has to be withdrawn. The effects of both treatments are explained in the light of new results. The reaction of wool with glutaraldehyde leads to a stabilization of the fiber. Experiments with glutaraldehyde and primary alkyl amines as model componds revealed that the cyclic form of the aldehyde gave the unstable N-alkyl-2,6-dihydroxypiperidine, which either looses water to give N-alkyldihydropyridine or condenses with 2,6-dihydroxytetrahydropyran to yield a copolyether which was isolated. According to recent publications, crosslinking of proteins by glutaraldehyde is due to the formation of quaternary pyridinium compounds.