Nanoparticles of nucleotide-free analogue of vitamin B formed in protein nanocarriers and their neuroprotective activity in vivo.

Recently, we have described the first supermolecular nanoentities of vitamin B derivative, viz. monocyano form of heptabutyl cobyrinate, unique nanoparticles with strong noncovalent intermolecular interactions, emerging optical and catalytic properties. Their nearest analogue, heptamethyl cobyrinate (ACCby), exhibits bioactivity.

Modulation of polyaniline memristive device switching voltage by nucleotide-free analogue of vitamin B.

Memristive devices offer essential properties to become a part of the next-generation computing systems based on neuromorphic principles. Organic memristive devices exhibit a unique set of properties which makes them an indispensable choice for specific applications, such as interfacing with biological systems. While the switching rate of organic devices can be easily adjusted over a wide range through various methods, controlling the switching potential is often more challenging, as this parameter is intricately tied to the materials used.

High Reactivity of Supermolecular Nanoentities of a Vitamin B Derivative in Langmuir-Schaefer Films Toward Gaseous Toxins.

Recently, we have described the first supermolecular nanoentities (SMEs) of a vitamin B derivative, viz., a monocyano form of heptabutyl cobyrinate ((CN)Cby), unique nanoparticles with strong noncovalent intermolecular interactions, and emerging optical and redox properties. In this work, the fast response of thin films based on the SMEs of the B derivative to gaseous toxins (viz.

meso-Bromination of cyano- and aquacobalamins facilitates their processing into Co(II)-species by glutathione.

Cyanocobalamin (CNCbl), a medicinal form of vitamin B, is resistant to glutathione (GSH), and undergoes intracellular processing via reductive decyanation producing the Co(II)-form of Cbl (Cbl(II)) mediated by the CblC-protein. Alteration of the CblC-protein structure might inhibit CNCbl processing. Here, we showed that introducing a bromine atom to the C10-position of the CNCbl corrin ring facilitates its reaction with GSH leading to the formation of Cbl(II) and cyanide dissociation.

Aquacobalamin Accelerates Orange II Destruction by Peroxymonosulfate via the Transient Formation of Secocorrinoid: A Mechanistic Study.

Besides its use in medicine, vitamin B (cobalamin) and its derivatives have found in numerous applications as catalysts. However, studies related to the activation of oxidants via cobalamin are scant. In this work, we showed how the addition of aquacobalamin (HOCbl) accelerates the destruction of azo-dye Orange II by peroxymonosulfate (HSO) in aqueous solutions.

Versatile enzymology and heterogeneous phenotypes in cobalamin complementation type C disease.

Nutritional deficiency and genetic errors that impair the transport, absorption, and utilization of vitamin B (B) lead to hematological and neurological manifestations. The cblC disease (cobalamin complementation type C) is an autosomal recessive disorder caused by mutations and epi-mutations in the gene and the most common inborn error of B metabolism. Pathogenic mutations in disrupt enzymatic processing of B, an indispensable step before micronutrient utilization by the two B-dependent enzymes methionine synthase (MS) and methylmalonyl-CoA mutase (MUT).

Mechanism of cyanocobalamin chlorination by hypochlorous acid.

Hypochlorous acid (HOCl) is a strong oxidant produced by myeloperoxidase. Previous work suggested that HOCl modifies the corrin ring of cobalamins to yield chlorinated species via mechanisms that are incompletely understood. Herein, we report a mechanistic study on the reaction between cyanocobalamin (CNCbl, vitamin B) and HOCl.

Catalytic effect of riboflavin on electron transfer from NADH to aquacobalamin.

Reduction of cobalamin by non-dedicated cellular reductases has been reported in earlier work, however, the sources of reducing power and the mechanisms are unknown. This study reports results of kinetic and mechanistic investigation of the reaction between aquacobalamin, HOCbl, and reduced β-nicotinamide adenine dinucleotide, NADH. This interaction leads to the formation of one-electron reduced cobalamin, cob(II)alamin, and proceeds via water substitution on aquacobalamin by NADH and further decomposition of NADH-Co(III) complex to cob(II)alamin and NADH.

Characterization of the complex between native and reduced bovine serum albumin with aquacobalamin and evidence of dual tetrapyrrole binding.

Serum albumin binds to a variety of endogenous ligands and drugs. Human serum albumin (HSA) binds to heme via hydrophobic interactions and axial coordination of the iron center by protein residue Tyr161. Human serum albumin binds to another tetrapyrrole, cobalamin (Cbl), but the structural and functional properties of this complex are poorly understood.

Studies on reaction of glutathionylcobalamin with hypochlorite. Evidence of protective action of glutathionyl-ligand against corrin modification by hypochlorite.

Glutathionylcobalamin (GSCbl), a tight complex of glutathione (GSH) with cobalamin(III), is readily oxidized to aquacobalamin by hypochlorite. Corrin macrocycle remains unmodified in the presence of threefold excess of hypochlorite, whereas aqua- and cyanocobalamins are partially transformed to chlorinated species under the same conditions. The suggested mechanism of reaction between GSCbl and hypochlorite involves subsequent oxidation of thiol and amino groups and dissociation of oxidized glutathione from Co(III)-ion.

Comparative studies of reaction of cobalamin (II) and cobinamide (II) with sulfur dioxide.

The kinetics of reactions of cobalamin (II) and cobinamide (II) with sulfur dioxide was studied by UV-visible (UV-vis) spectroscopy. Reaction results in oxidation of Co(II) center and involves two aquated SO moieties. The final product is suggested to be complex Co(III)-SO .

Reactions of aquacobalamin and cob(II)alamin with chlorite and chlorine dioxide.

Reactions of aquacobalamin (HO-Cbl(III)) and its one-electron reduced form (cob(II)alamin, Cbl(II)) with chlorite (ClO) and chlorine dioxide (ClO ) were studied by conventional and stopped-flow UV-Vis spectroscopies and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). ClO does not react with HO-Cbl(III), but oxidizes Cbl(II) to HO-Cbl(III) as a major product and corrin-modified species as minor products. The proposed mechanism of chlorite reduction involves formation of OCl that modifies the corrin ring during the course of reaction with Cbl(II).

Kinetics and mechanism of oxidation of super-reduced cobalamin and cobinamide species by thiosulfate, sulfite and dithionite.

We studied the kinetics of reactions of cob(I)alamin and cob(I)inamide with thiosulfate, sulfite, and dithionite by UV-Visible (UV-Vis) and stopped-flow spectroscopy. We found that the two Co(I) species were oxidized by these sulfur-containing compounds to Co(II) forms: oxidation by excess thiosulfate leads to penta-coordinate complexes and oxidation by excess sulfite or dithionite leads to hexa-coordinate Co(II)-SO2(-) complexes. The net scheme involves transfer of three electrons in the case of oxidation by thiosulfate and one electron for oxidation by sulfite and dithionite.

Comparative study of reaction of cobalamin and cobinamide with thiocyanate.

The interaction of Co(III) and Co(II) cobalamin (Cbl) and cobinamide (Cbi) with thiocyanate was examined with UV-vis and EPR spectra. S/N-linkage isomerism was explored on Co(III) and Co(II) Cbl and Cbi models using density functional theory (DFT; BP86, B3LYP). Performed calculations suggest the prevalence of isothiocyanato isomers over thiocyanato complexes on both Co(III) and Co(II) centers.