The acylation of wool with active esters

Abstract

The reaction of wool with radioactive acetylating agents, viz. p-nitrophenyl [1-¹⁴C]acetate, N-[l-¹⁴C]acetoxysuccinimide, p-nitrophenyl [l-¹⁴C]-n-decanoate, and di-p-nitrophenyl [l,10-¹⁴C]sebacate, has been studied using acetic acid, triethylamine, or (in some cases) imidazole as catalyst. An indirect method of amino acid analysis, in which the acylated wool is first treated with 1-fluoro-2,4-dinitrobenzene, was used to estimate the sites and extents of acylation. However, it was found that the method was unsatisfactory for studying the acylation of seryl, threonyl, and tyrosyl residues. In contrast to previous workers, we found that the above active esters are not specific for the ?-amino groups of lysyl residues but react also with the hydroxyl groups of seryl, threonyl, and tyrosyl residues, especially under vigorous conditions. The O-acyl groups could be selectively removed by treating the acylated wool with hydroxylamine, although the conditions required were more vigorous than those necessary for the removal of O-acyl groups from soluble proteins. Using these conditions the relative rates of N- and O-acylation of wool with a variety of (radioactive) acylating agents were measured.