Tetrazole derivatives and matrices as novel cobalamin coordinating compounds

Abstract

Cobalamin (Cbl, vitamin B 12 ) consists of two moieties: (i) the corrin ring with the central Co-ion in the oxidation states Co 3+/2+/1+ and (ii) the nucleotide side chain. The lower position of the ring is typically occupied by the nucleotide base (Bzm), whereas the upper surface coordinates exchangeable ligands. We have found that amino-tetrazole can coordinate to H 2 O AE Cbl (Co 3+ ) with K d = 10 À5 -10 À6 M. A specific group (presumably tetrazole, TZ) can be easily created in CNBr-activated Sepharose by treatment with N À 3 . The prepared matrix (STZ) contained %10 mM of the active groups, which bound H 2 O AE corrinoids with K d = 10 À5 -10 À6 M. Stability of STZCbl bonds gradually increased and reached K d = 10 À7 M over 10-20 h (20°C, pH 6-7). This effect can be ascribed to partial displacement of Bzm and coordination of TZ to the lower position. The binding was most efficient at pH 4-7 and low ionic strength, yet, noticeable adsorption took place even at extreme conditions, pH 1-9 and I = 0-2 M. Reduced corrins (Co 2+ ) also exhibited high affinity for STZ. The bound ligands could be eluted as H 2 O AE Cbl (pH 0), HO AE Cbl (pH 14) or diCN AE Cbl (pH 9-12, CN À ). The adsorbent is applicable for one-step purification of corrins from a crude extract; separation of aquo-and diaquo-forms; specific capturing of H 2 O AE Cbl from a mixture containing organo-Cbls or protein-bound Cbl, analysis of peptide-Cbl dissociation kinetics, etc.

Comparison of Recombinant Human Haptocorrin Expressed in Human Embryonic Kidney Cells and Native Haptocorrin

“…Prior to AP measurements, rhHC was saturated with an excess of aquo-Cbl, free aquo-Cbl was bound to the specific tetrazole adsorbent [41] , whereupon the spectrum of rhHC·Cbl was recorded and compared to the control sample (buffer + aquo-Cbl + adsorbent). After subtraction of the control spectrum, the absorbance ratio and AP were calculated.…”

New α‐amino phenylalanine tetrazole ligand for immobilized metal affinity chromatography of proteins

“…From the molecular structure, it can be found that tetrazole is a strong electron donor and shows strong ability to chelate with transition metal ions compared with carboxylic group. For instance, the chelate complex formed by Ncarboxybenzyloxy(Cbz) a-amino tetrazole and Zn 2+ would only dissociate until the concentration of HCl solution reaches 3.0 mol/L [16], and tetrazole-based Sepharose made by Fedosov et al [23] showed an efficient coordinating ability to Co 2+ in Cobalamin. Accordingly, tetrazole may be a potential ligand for IMAC.…”

Development of an electrochemical DNA biosensor for the detection of vitamin B12 (cyanocobalamin) at a carbon paste modified electrode with a manganese(II) complex

“…Vitamins of group B ensure the normal performance of human body through participation in the biosynthesis of proteins and functioning of the central nervous, cardiovascular and gastrointestinal systems [1,2]. In specific, vitamin B 12 or cobalamin is an organometallic cofactor with a complex structure [1,2].…”

“…In specific, vitamin B 12 or cobalamin is an organometallic cofactor with a complex structure [1,2]. Vitamin B 12 exhibits a rich redox chemistry centered on the cobalt atom, where the Co III in the vitamin B 12 can be reduced reversibly to Co II and further reduced to Co I [3,4].…”