Application of emission (Co) Mössbauer spectroscopy in bioscience

Cobalt is an essential trace element with a broad range of physiological and biochemical functions. However, biochemical speciation of cobalt and structural investigations of cobalt-containing complexes with biomacromolecules are challenging, as the participation of cobalt in physiological processes is limited by its very low concentrations. Emission Mössbauer spectroscopy (EMS), with the radioactive Co isotope as the most widely used nuclide, is several orders of magnitude more sensitive than its Fe absorption variant which has had a rich history of applications in bioscience. Nevertheless, owing to specific difficulties related to the necessity of using radioactive Co in samples under study, applications of EMS in biological fields have so far been sparse. In this communication, the EMS applicability to studying biological objects as well as some specific aspects of the EMS methodology are considered in order to draw attention to the unique structural information which can be obtained non-destructively in situ. Chemical consequences (after-effects) of the nuclear transition (Co/Fe), which provide additional information on the electron acceptor properties of the proximate chemical microenvironment of the metal ions, are also considered. The data presented demonstrate that EMS is a sensitive tool for monitoring the chemical state and coordination of cobalt species in biological matter and in biomacromolecular complexes (metalloenzymes), providing valuable structural information at the atomic level. q 2004 Elsevier B.V. All rights reserved.