Semisynthetic human [[3H2]Phe1]proinsulin.

Biosynthetic human proinsulin (obtained by recombinant DNA techniques) was used as the starting material for the preparation, by semisynthetic methods, of [3H]proinsulin with the label at the N-terminal phenylalanine residue. The labelled proinsulin was characterized by its retention time on reversed-phase h.p.l.c., by polyacrylamide-gel electrophoresis, by the time course of its enzymic conversion into insulin and by chromatographic analysis after extensive proteolytic degradation. The specific radioactivity of the product was 5 Ci/mmol. Experimental details of the preparation of human [[3H]Phe1]proinsulin, the isolation of this product by isocratic h.p.l.c. and gel filtration, and further characterization of protein intermediates have been deposited as supplement SUP 50138 (12 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on prepayment [see Biochem. J. (1987) 241, 5].