Methyl transfer reactions catalyzed by cobalamin-dependent enzymes: Insight from molecular docking.

Methyl transfer reactions, mediated by methyltransferases (MeTrs), such as methionine synthase (MetH) or monomethylamine: CoM (MtmBC), constitute one of the most important classes of vitamin B12-dependent reactions. The challenge in exploring the catalytic function of MeTrs is related to their modular structure. From the crystallographic point of view, the structure of each subunit has been determined, but there is a lack of understanding of how each subunit interacts with each other. So far, theoretical studies of methyl group transfer were carried out for the structural models of the active site of each subunit. However, those studies do not include the effect of the enzymatic environment, which is crucial for a comprehensive understanding of enzyme-mediated methyl transfer reactions. Herein, to explore how two subunits interact with each other and how the methyl transfer reaction is catalyzed by MeTrs, molecular docking of the functional units of MetH and MtmBC was carried out. Along with the interactions of the functional units, the reaction coordinates, including the Co-C bond distance for methylation of cob(I)alamin (CoICbl) and the C-S bond distance in demethylation reaction of cob(III)alamin (CoIIICbl), were considered. The functional groups should be arranged so that there is an appropriate distance to transfer a methyl group and present results indicate that steric interactions can limit the number of potential arrangements. This calls into question the possibility of SN2-type mechanism previously proposed for MeTrs. Further, it leads to the conclusion that the methyl transfer reaction involves some spatial changes of modules suggesting an alternate radical-based pathway for MeTrs-mediated methyl transfer reactions. The calculations also showed that changes in torsion angles induce a change in reaction coordinates, namely Co-C and C-S bond distances, for the methylation and demethylation reactions catalyzed both by MetH and MtmBC.

Cold Plasma as an Innovative Construction Method of Voltammetric Biosensor Based on Laccase.

Development of new, faster methods of biosensor construction is a huge challenge for current science and industry. In this work, biosensor construction was carried out using a new soft plasma polymerization (SPP) method in which a bio-recognition layer of laccase enzyme was polymerized and bonded to a glassy carbon electrode (GCE) substrate under atmospheric pressure with a corona discharge jet. Laccase belongs to the oxidoreductase enzyme group with four copper atoms in its active center. Application of the corona SPP plasma method allows reduction of the time needed for biosensor construction from several hours to minutes. The presented work includes optimization of the laccase bio-recognition layer deposition time, structural studies of the deposited laccase layer, as well as study of the fabricated biosensor applicability for the determination of Rutin in real pharmaceutical samples. This method produces a biosensor with two linear ranges from 0.3 µmol/dm³ to 0.5 µmol/dm³ and from 0.8 µmol/dm³ to 16 µmol/dm³ of Rutin concentration. Results shown in this work indicate that application of the one-step, corona SPP method enables biosensor construction with comparable analytical parameters to biosensors fabricated by conventional, multi-step, wet methods.

Laccase Enzyme Polymerization by Soft Plasma Jet for Durable Bioactive Coatings.

Conventional pin-to-point continuous wave Helium Corona plasma discharge was successfully used in Soft Plasma Polymerization (SPP) processes to immobilize into water and onto glass polymerized bioactive Cerrena unicolor laccase coatings. The coatings were tested for bioactivity and durability under water wash. The coatings showed up to 59% bioactivity relative to the native laccase in water deposition, undoubtedly due to damage to and fragmentation of monomer molecules by the active, energetic species in the plasma. However, plasma deposited laccase coatings on glass delivered 7 times the laccase activity of the same non-plasma deposition process in the coating after water wash. This latter result would seem to be due to the ability of the plasma to both crosslink monomer and more strongly bond it to the glass surface by a combination of surface cleaning and the creation of active, high energy sites in both glass and laccase molecules. FTIR analysis indicated that the core copper containing moieties at the centre of the molecule largely remain undamaged by this plasma type so that bonding and cross-linking reactions are likely to mainly involve species around the outer perimeter of the molecule. The chemical composition and structure of laccase biocoatings deposited by Corona SPP are described. The combination of the coating performance parameter values for retained activity and durability under water wash indicates that a relatively simple Corona plasma process for deposition of biocoatings, which directly polymerizes the monomer with no added matrix or encapsulant material, may offer enhanced solutions for biocatalyst, sensor or lab-on-a-chip applications.

Theoretical predictions of anti-corrosive properties of THAM and its derivatives.

We present quantum chemical theoretical estimations of the anti-corrosive properties of THAM (tris(hydroxymethyl)aminomethane) and three derivatives that differ in the number of benzene rings: THAM-1 (2-amino-3-hydroxy-2-(hydroxymethyl) propylobenzoate), THAM-2 (2-amino-2-(hydroxymetyl)prapan-1,3-diyldibenzoate) and THAM-3 (2-amino-propan-1,2,3-triyltribenzoate). Fourteen exchange-correlation functionals based on the density functional theory (DFT) were chosen for quantum chemical study of THAM derivatives. The objective was to examine the effect of benzene rings on potential anti-corrosive properties of THAM compounds. The results indicate that the addition of benzene rings in THAM derivatives is likely to significantly enhance electrostatic bonding of a THAM-based coating to a presented metal surface and, thus, its adhesion and long-term effect in corrosion inhibition. Whereas it is clear that all three derivatives appear to be superior in their bonding characteristics to pure THAM, the potential order of merit between the three is less clear, although THAM-3 presents as possibly superior.

Structural and electronic properties of an [(Al2O3)4](+) cluster.

Density functional theory (DFT) has been applied to investigate the structural and electronic properties of an [(Al2O3)4](+) cluster. Since there is no structural data available from experiment, the geometry of the cluster was obtained based on a model which produced the best agreement with vibrational IR-MPD data. A range of different exchange-correlation functionals were tested, and it was concluded that the best spectral agreement was produced using the CAM-B3LYP and B3LYP functionals, respectively. To further characterize the properties of the cluster, natural bond order analysis was performed, and it was concluded that an appropriate description for the system is [Al8O12](+). The frontier orbitals and spin densities of both cation and neutral systems were considered, and it was concluded that the unrestricted singlet and triplet spin densities of the neutral [Al8O12] system were nearly degenerate, representing a di-radical, with the triplet state being lower in energy.