The thermal decomposition of group IIB metal(II) halide complexes. Part III. Low frequency infrared spectra and thermal behaviour of N,N,N′-trimethylethylenediamine complexes

The group IIb metal dihalide-N,N,N′-trimethylethylenediamine complexes are described. Low frequency infrared spectroscopic studies and conductance data have provided evidence for the formulation and structure of the complexes. The thermal behaviour of these complexes has been examined by thermogravimetry and differential scanning calorimetry. For cadmium and mercury complexes complete loss of ligand occurred followed eventually by sublimation of the metal halide, whereas the zinc complexes sublimed unchanged.     

Myrmechis bakhimensis D. Maity, N. Pradhan ＆ G. G. Maiti, a new species of Orchidaceae from Sikkim Himalaya

Myrmechis bakhimensis D. Maity,N. Pradhan & G. G. Maiti (Orchidaceae),a new species from Sikkim Himalaya,is described and illustrated. The new species most closely resembles M. japonica (Reichb.) Rolfe and M. chinensis Rolfe with similar shape and size of lamina and the “T”-shaped epichile,but differs by the perfectly glabrous and eciliate floral bract,5-nerved dorsal sepal,and emarginate,mucronate epichile.     

Production of N,N′-diacetylchitobiose from chitin using temperature-sensitive chitinolytic enzyme preparations of Aeromonas sp. GJ-18

Summary N,N′-diacetylchitobiose was produced from chitin as a major hydrolytic product by controlling the ratio of β-N-acetylglucosaminidase to N,N′-diacetylchitobiohydrolase activities in the crude enzyme preparation of Aeromonas sp. GJ-18. When the enzyme preparation was preincubated at 50 °C, β-N-acetylglucosaminidase was nearly inactivated, while the N,N′-diacetylchitobiohydrolase was still active. Thus, the composition of chitin oligosaccharides depended on the preincubation temperature of the crude enzyme preparations. Typically, after 7 days of incubation with the substrate chitin, 78.9 and 56.6% of N,N′-diacetylchitobiose yields were obtained from swollen α-chitin and powdered β-chitin, respectively, with enzyme preparations that had been pretreated at 50 °C for 60 min.     

Microbial metabolism of aromatic nitriles. Enzymology of C–N cleavage by Nocardia sp. (Rhodochrous group) N.C.I.B. 11216

1. An organism utilizing benzonitrile as sole carbon and nitrogen source was isolated by the enrichment-culture technique and identified as a Nocardia sp. of the rhodochrous group. 2. Respiration studies indicate that nitrile degradation proceeds through benzoic acid and catechol. 3. Cell-free extracts of benzonitrile-grown cells contain an enzyme that catalyses the conversion of benzonitrile directly into benzoic acid without intermediate formation of benzamide. 4. This nitrilase enzyme was purified by DEAE-cellulose chromatography and gel filtration on Sephadex G-100 in the presence and absence of substrate. The purity of the enzyme was confirmed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing on polyacrylamide gel. 5. The enzyme shows a time-dependent substrate-activation process in which the substrate catalyses the association of inactive subunits of mol.wt. 45000 to form the polymeric 12-unit active enzyme of mol.wt. 560000. The time required for complete association is highly dependent on the concentration of the enzyme, temperature and pH. 6. The associated enzyme has a pH optimum of 8.0 and K(m) with benzonitrile as substrate of 4mm. The activation energy of the reaction as deduced from the Arrhenius plot is 51.8kJ/mol. 7. Enzyme activity is inhibited by thiol-specific reagents and several metal ions. 8. Studies with different substrates indicate that the nitrilase is specific for nitrile groups directly attached to the benzene ring. Various substituents in the ring are compatible with activity, though ortho-substitution, except by fluorine, renders the nitrile invulnerable to attack. 9. The environmental implications of these findings and the possible significance of the enzyme in the regulation of metabolism are discussed.     

Antimicrobial efficacy of some N,N’-Dialkyl-N,N’-dimethyl-1, 6-hexanediamine dioxides

A total of 17 N,N'-dialkyl-N,N'-dimethyl-1,6-hexanediamine dioxides were tested for activity against three microorganisms. A relationship was found between the length of the alkyl substituent and antimicrobial activity.