Phenyl isocyanate protein derivatives and their immunological properties

Abstract

Phenyl and p-bromophenyl isocyanate derivatives of several amino-acids were prepared, including those of [alpha]- and [epsilon]-amino-n-hexoic acids. Inhibition, by these phenylcarbamido-acids, of the pre-cipitin reaction between phenylcarbamido-proteins and corresponding antisera was studied. Similar inhibition of complement fixation was also obtained. Phenylcarbamido-acids from lysine and [epsilon]-amino-n-hexoic acid gave complete inhibition, whereas equivalent amts. of the derivatives of [alpha]-amino-n]-hexoic acid, leucine, alanine, tyrosine, etc., gave moderate-inhibition only. These serologic inhibition tests offer, therefore, strong support for the view that the free amino-groups of the intact protein molecule are the [alpha]-amino-groups of the lysine molecules.