Specific labelling of sulfhydryl-containing biomolecules with redox-active N-(ferrocenyl)iodoacetamide

Abstract

The synthesis, characterisation, X-ray crystal structure and electrochemical properties of a new redox-active labelling reagent, N-(ferrocenyl)iodoacetamide (Fc-IAA), are reported. This compound exhibits a reversible ferrocenium/ferrocene couple at ca. +0.345 V vs. SCE at a sweep rate of 100 mV s⁻¹ in CH₃CN at 298 K, and two irreversible reduction waves at ca. −1.324 and −2.048 V, attributable to the reduction of the iodoacetamide group. Since the iodoacetamide moiety can react specifically with the sulfhydryl group, Fc-IAA has been coupled to various biomolecules including a sulfhydryl-modified oligonucleotide, cysteine, glutathione and sulfhydryl-modified bovine serum albumin. The electrochemical properties of the bioconjugates have also been investigated.