Water-soluble carrier proteins having carboxyl spacer groups.

Abstract

Three water-soluble bovine serum albumin derivatives with carboxyl spacer groups have been synthesized as carrier proteins for direct preparation of conjugates between proteins and low molecular haptens with amino groups. N-Glycylaminomethanesulfonic acid, a newly developed solubilizing reagent for proteins, was first introduced into bovine serum albumin through its carboxyl groups. After the methylation of carboxyl groups remaining unreacted in the modified albumin, N-succinylglycine and N-bromoacetyl-β-alanine, both carboxyl spacer reagents, were reacted with the amino or imidazole groups of the modified albumin, respectively, to give two water-soluble albumin derivatives. Another water-soluble albumin derivatives. Another water-soluble albumin derivative was obtained by treating the modified albumin with N-bromoacetyl-β-alanine followed by amidination of the remaining amino groups of the albumin with methylacetimidate. Glycine ethyl ester, selected as a model hapten that has an amino group, was reacted with these albumin derivatives to form conjugates, and 4-15 ester moieties can be incorporated into one molecule of the albumin derivatives without loss of their water-solubility.