Incubation at approximately physiological conditions of amino acids, peptides, and proteins with 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea or cyclohexyl isocyanate resulted in carbamoylation of the alpha-amino groups of amino acids, the terminal amino groups of peptides and proteins and the epsilon-amino groups of lysine moieties. Carbamoylation of the alpha-amino groups and the terminal ami...