Abstract: Proteins are radiolabeled with radionuclides of technetium or rhenium by a process in which the disulfide bonds of the protein are first partially reduced with stannous salts or other disulfide reducing agents, all substances other than the desired reduced protein removed, by size exclusion chromatography or other purification means, and a specified, smaller amount of pertechnetate or perrhenate reducing agent, such as a stannous salt, is added to the reduced protein in a manner such that further reduction of the protein is limited. Pertechnetate or perrhenate is then added to the mixture of the reduced protein and the pertechnetate or perrhenate reducing agent; the pertechnetate or perrhenate is reduced and becomes strongly bonded to the protein via the sulfhydryl groups previously exposed by reduction of disulfide groups. The reduced protein and pertechnetate or perrhenate reducing agent can be indefinitely stored frozen or lyophilized.

Abstract: Proteins containing one or more disulfide bonds are radiolabeled with radionuclides of technetium or rhenium for use in diagnosis and treatment of a variety of pathologic conditions. Radiolabeling is accomplished by partial reduction of the disulfide bonds of the protein using Sn (II), or using other reducing agents followed by the addition of Sn (II), removal of excess reducing agent and reduction by-products, and addition of a specified amount of pertechnetate or perrhenate reducing agent, such as stannous tartrate, with the addition accomplished in such manner that further reduction of the protein is limited. The resulting product may be stored frozen or lyophilized, with radiolabeling accomplished by the addition of pertechnetate or perrhenate solution.