Kinetics of befunolol reductase from rabbit liver

The kinetic mechanism for the reduction of befunolol catalyzed by befunolol reductase from rabbit liver was investigated. From the initial velocity analysis, product inhibition and coenzyme binding studies, the reduction of befunolol was found to proceed through an ordered Bi Bi mechanism, in which beta-nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) binds to the enzyme firstly and NADP+ leaves lastly. NADPH bound to the free enzyme at a molar ratio of 1:1. Furthermore, the result of dead-end inhibition by Cibacron blue F3GA, a nucleotide analogue which binds to many enzymes, was consistent with the ordered Bi Bi mechanism for the enzyme.     

Purification and characterization of befunolol reductase from rabbit liver

An enzyme (befunolol reductase) which catalyzes the reduction of befunolol to dihydrobefunolol was purified from the cytosolic fraction of rabbit liver to homogeneity by various chromatographic techniques. Befunolol reductase had molecular weights of 29000 on sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and 34000 on gel filtration. The enzyme required reduced nicotinamide adenine dinucleotide phosphate (NADPH) as a cofactor and showed an optimal pH of 6.5. The apparent Km and Vmax values of the enzyme for the reduction of befunolol were 1.7 mM and 4.4 units/mg, respectively. Flavonoids, sulfhydryl reagents, heavy metals and coumarins strongly inhibited the enzyme. The enzyme catalyzed the reduction of a variety of aromatic ketones. In addition to befunolol, some ketone-containing drugs such as daunorubicin and levobunolol were efficiently reduced by the enzyme. On the basis of substrate specificities for steroids, befunolol reductase purified from the cytosolic fraction of rabbit liver appeared to be a 3 alpha-hydroxysteroid dehydrogenase.     

Studies relating to the accuracy of in vivo measurements of liver and kidney cadmium

A greater understanding of the inaccuracies involved inin vivo measurements of liver and kidney cadmium by neutron activation was necessary. Studies were therefore carried out, using phantoms, into the effect onin vivo measurement accuracy of organ depth and organ mass. In addition an independentin vitro technique was developed, and used to analyse autopsy samples from three people previously measuredin vivo, thus making direct comparisons possible. No evidence of bias in thein vivo results was found, but the need to correct for organ mass and depth was highlighted. Current measurement procedures result in residual uncertainties of ±25%.     

Studies on metal-ammonia reduction and reductive methylation of naphthalenes

Reductive methylation of 1-carbomethoxy-4, 6-dimethoxynaphthalene in anhydrous ammonia gave 1-methyl-1-carbomethoxy-6-methoxy-1, 4-dihydronaphthalene in good yield. Metal ammonia reduction of the ketones 12 and 18 provided an expedient pathway for the synthesis of the ,β-unsaturated ketones 17 and 19 respectively.     

Studies on metabolites and metabolic pathways of bulleyaconitine A in rat liver microsomes using LC‐MSn combined with specific inhibitors

Bulleyaconitine A (BLA) from Aconitum bulleyanum plants is usually used as anti‐inflammatory drug in some Asian countries. It has a variety of bioactivities, and at the same time some toxicities. Since the bioactivities and toxicities of BLA are closely related to its metabolism, the metabolites and the metabolic pathways of BLA in rat liver microsomes were investigated by HPLC–MSⁿ. In this research, the 12 metabolites of BLA were identified according to the results of HPLC‐MSⁿ data and the relevant literature. The results showed that there are multiple metabolites of BLA in rat liver microsomes, including demethylation, deacetylation, dehydrogenation deacetylation and hydroxylation. The major metabolic pathways of BLA in rat liver microsomes were clarified by HPLC‐MS combined with specific inhibitors of CYP450 isoforms. As a result, CYP3A and 2C were found to be the principal CYP isoforms contributing to the metabolism of BLA. Moreover, CYP2D6 and 2E1 are also more important CYP isoforms for the metabolism of BLA. While CYP1A2 only affected the formation rate of M11, its effect on the metabolism of BLA is very small. Copyright © 2014 John Wiley & Sons, Ltd.     

Studies in reduction of molecular weight of polypropylene

Polypropylene (PP) is the most widely used polyolefin, due to its high mechanical strength and better processability in comparison to the others in its group. Conventional methods of polymerisation result in high molecular weights of PP. However, high molecular weights are not required for several applications. To overcome this problem controlled reduction in molecular weight of PP in presence of free radicals, in solution, is proposed. Four commonly available free radical generators viz: benzoyl peroxide (BPO), azo- iso-bis butyronitrile (AIBN), t-butyl hydroperoxide (TBHP) and dicumyl peroxide (DCP) were used to bring about reduction in molecular weight of PP. Effect of the free radical generator concentration, reaction time, reaction temperature and reaction medium (toluene, xylene and decalin) on the extent of molecular weight reduction was studied. The effect of this molecular weight reduction on mechanical, thermal, rheological and crystalline properties of the polymer was also studied. With proper selection of initiator and reaction conditions, it was possible to obtain low molecular weight branched PP with improved mechanical and thermal properties.     

Studies on ligand binding of kidney bean leghemoglobin.

Absorption spectra of different ligand derivative;s of kidney bean leghemoglobin alpha have been recorded. The effect of pH on the absorption spectra of kidney bean leghemoglobin alpha has been studied. The pK of the acid-alkaline transition of the heme-linked water molecule is 8.25 and the pK for the acid dissociation of the heme group is 4.03. Affinities of kidney bean leghemoglobin for two different types of ligands have been studied in comparison with soybean leghemoglobins alpha and c and sperm whale myoglobin. All these leghemoglobins have similar affinities for the small anionic ligand fluoride ion, and they are only slightly more accessible to this ligand than is sperm whale myoglobin. Differences in the primary structure or in conformation of these proteins are reflected in the affinity for the bulky ligand imidazole. The accessibility to imidazole increases in the order sperm whale myoglobin less than soybean Lbalpha less than soybean Lbc less than kidney bean Lbalpha, and also low spin Lbalpha less than high spin Lbalpha. The results are discussed with respect to the amino acid sequences of the leghemoglobins.     

Studies on the determination of diacetyl guanfubase A concentration in rabbit plasma and pharmacokinetics

A gas chromatographic method for monitoring diacetyl guanfubase A in plasma is described. The procedure involved a single solvent extraction of drug from rabbit plasma into ethyl acetate with guanfubase A as an internal standard. The extract was analyzed subsequently on a gas chromatograph equipped with a hydrogen flame ionization detector. The recovery was 86.43% +/- 6.90% (+/- SD); the RSD of within-day and between-day was 2.81%-5.26% and 5.22%-8.24%, respectively; the regression line was linear over the concentration range of 25-200 micrograms/mL, the limit of detection was 10 micrograms/mL. No endogeneous interference was found in chromatograms of the biological samples. This method was applied to the pharmacokinetic study of diacetyl guanfubase A in rabbits.