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ISSN 1998-9539

Effect of Bovine Serum Albumin on Redox and Ligand Exchange Reactions Involving Aquacobalamin

Ilia A. Dereven’kov,@ Sergei V. Makarov, and Pavel A. Molodtsov

This paper is dedicated to prof. Rudi van Eldik on the occasion of his 75th birthday.

His works on vitamin B12 have been a source of inspiration for us.

Institute of Macroheterocyclic Compounds, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Russia

@Corresponding author E-mail: derevenkov@gmail.com

 

Bovine serum albumin (BSA) is capable of binding aquacobalamin (H2OCbl) by two different modes, i.e. (i) via hydrogen bonding or π-π interactions without substitution of water molecule or (ii) via water substitution to give amino BSA–Cbl(III) complex. In this work, we showed that the first type of complex exhibits the same reactivity toward ascorbic acid and thiocyanate as H2OCbl. The amino BSA–Cbl(III) complex is substantially less reactive toward ascorbic acid, thiocyanate and sulfite than H2OCbl. Using sulfite, we showed that ligand exchange in this complex proceeds via two pathways, i.e. via (i) a direct substitution of BSA by sulfite species or (ii) a slow dissociation of BSA from the complex followed by rapid sulfite binding by Cbl(III).