Degradation of substituted benzoic acids by a Micrococcus species

Abstract a Micrococcus sp. isolated by isophthalate enrichment, utilized 8 of the 13 substituted benzoic acids tested as the sole source of carbon and energy. The organism degraded benzoic acid and anthranilic acid through the intermediate formation of catechol. While salicylate is metabolized through genetisic acid, p-hydroxybenzoic acid is degraded through protocatechuic acid. The organism grew well on isophthalate but failed to utilize phthalate and terphthalate. Catechol disoxygenase, gentisate dioxygenase and protocatechuate dioxygenase activities were shown in the cell-free extracts. Catechol and protocatechuate are further metabolized through an ortho-cleavage pathway.

Mammalian brain plasma membranes: Isolation, enzymatic, and chemical characterization

Two variants of a simplified procedure for the isolation of plasma membrane fractions from monkey and rat brains, are described. The preparations show marked enrichments in the marker enzymes, (Na+-K+) adenosine triphosphatase, acetylcholinesterase, 5′-nucleotidase and adenylate cyclase. Lipid analysis and a protein electrophoretic pattern are presented. An enzymatic check has been made to assess for contamination by other cellular organelles. The amino acid composition of brain membrane proteins show a resemblance to the reported composition of erythrocyte ghost proteins but differ from myelin proteins.

Microbial metabolism of phenolic amines: degradation of dl-synephrine by an unidentified arthrobacter

Microorganisms capable of degrading dl-synephrine were isolated from soil of Citrus gardens by enrichment culture, with dl-synephrine as the sole source of carbon and nitrogen. An organism which appears to be an arthrobacter, but which cannot be identified with any of the presently recognized species was predominant in these isolates. It was found to metabolize synephrine by a pathway involving p-hydroxyphenylacetaldehyde, p-hydroxyphenylacetic acid, and 3,4-dihydroxyphenylacetic acid as intermediates. Some of the enzymes of this pathway were demonstrated in cell-free extracts. An aromatic oxygenase, which could also be readily obtained in a cell-free system, was found to degrade 3,4-dihydroxyphenylacetic acid by meta cleavage.

The nonplanar peptide unit III. Quantum chemical calculations for related compounds and experimental X-ray diffraction data

The possible nonplanar distortions of the amide group in formamide, acetamide, N-methylacetamide, and N-ethylacetamide have been examined using CNDO/2 and INDO methods. The predictions from these methods are compared with the results obtained from X-ray and neutron diffraction studies on crystals of small open peptides, cyclic peptides, and amides. It is shown that the INDO results are in good agreement with observations, and that the dihedral angles N and defining the nonplanarity of the amide unit are correlated approximately by the relation N = -2, while C is small and uncorrelated with . The present study indicates that the nonplanar distortions at the nitrogen atom of the peptide unit may have to be taken into consideration, in addition to the variation in the dihedral angles (,), in working out polypeptide and protein structures.

Chemical modification studies on Abrus agglutinin Involvement of tryptophan residues in sugar binding

The galactose-binding lectin from the seeds of the jequirity plant (Abrus precatorius) was subjected to various chemical modifications in order to detect the amino acid residues involved in its binding activity. Modification of lysine, tyrosine, arginine, histidine, glutamic acid and aspartic acid residues did not affect the carbohydratebinding activity of the agglutinin. However, modification of tryptophan residues carried out in native and denaturing conditions with N-bromosuccinimide and 2- hydroxy-5-nitrobenzyl bromide led to a complete loss of its carbohydrate-binding activity. Under denaturing conditions 30 tryptophan residues/molecule were modified by both reagents, whereas only 16 and 18 residues/molecule were available for modification by N-bromosuccinimide and 2-hydroxy-5-nitrobenzyl bromide respectively under native conditions. The relative loss in haemagglutinating activity after the modification of tryptophan residues indicates that two residues/molecule are required for the carbohydrate-binding activity of the agglutinin. A partial protection was observed in the presence of saturating concentrations of lactose (0.15 M). The decrease in fluorescence intensity of Abrus agglutinin on modification of tryptophan residues is linear in the absence of lactose and shows a biphasic pattern in the presence of lactose, indicating that tryptophan residues go from a similar to a different molecular environment on saccharide binding. The secondary structure of the protein remains practically unchanged upon modification of tryptophan residues, as indicated by c.d. and immunodiffusion studies, confirming that the loss in activity is due to modification only.

Thermal degradation of polystyrene

The importance of the study of thermal degradation of polymeric fuels arises from their role in the combustion of solid propellants. Estimation of the condensed-phase heat release during combustion can be facilitated by the knowledge of the enthalpy change associated with the polymer degradation process. Differential scanning calorimetry has been used to obtain enthalpy data. Kinetic studies on the polymeric degradation process have been carried out with the following objectives. The literature values of activation energies are quite diverse and differ from author to author. The present study has tried to locate possible reasons for the divergence in the reported activation energy values. A value of 30 kcal has been obtained and found to be independent of the technique employed. The present data on the kinetics support to chain-end initiation and unzipping process. The activation energies are further found to be independent of the atmosphere in which the degradation of polymer fuel is carried out. The degradation in air, N2, and O2 all yield a value of 30 kcal/mole for the activation energies.

A model for doped-oxide-source diffusion with a chemical reaction at the silicon-silicon dioxide interface

A mathematical model for doped-oxide-source diffusion is proposed. In this model the concept of segregation of impurity at the silicon-silicon dioxide is used and also a constant of “rate limitation” is introduced through a chemical reaction at the interface.

Primary structure of a Thomsen-Friedenreich-antigen-specific lectin, jacalin [Artocarpus integrifolia (jack fruit) agglutinin]. Evidence for the presence of an internal repeat

Jacalin [Artocarpus integrifolia (jack fruit) agglutinin] is made up of two types of chains, heavy and light, with M(r) values of 16,200 +/- 1200 and 2090 +/- 300 respectively (on the basis of gel-permeation chromatography under denaturing conditions). Its complete amino acid sequence was determined by manual degradation using a 4-dimethylaminoazobenzene 4'-isothiocyanate double-coupling method. Peptide fragments for sequence analysis were obtained by chemical cleavages of the heavy chain with CNBr, hydroxylamine hydrochloride and iodosobenzoic acid and enzymic cleavage with Staphylococcus aureus proteinase. The peptides were purified by a combination gel-permeation and reverse-phase chromatography. The light chains, being only 20 residues long, could be sequenced without fragmentation. Amino acid analyses and carboxypeptidase-Y-digestion C-terminal analyses of the subunits provided supportive evidence for their sequence. Computer-assisted alignment of the jacalin heavy-chain sequence failed to show sequence similarity to that of any lectin for which the complete sequence is known. Analyses of the sequence showed the presence of an internal repeat spanning residues 7-64 and 76-130. The internal repeat was found to be statistically significant.

Synthesis, characterization, thermal degradation, and comparative chain dynamics studies of weak-link polysulfide polymers

Synthesis, spectroscopic and thermal characterization of two new classes of polysulfide polymers: poly[1(phenoxymethyl) ethylene polysulfide] (PPMEP), and poly [1-(phenoxy) ethylene polysulfide] (PPEP) is presented. The direct pyrolysis mass spectrometry (DP-MS) technique, used to study the thermal degradation behavior of these polysulfide polymers, indicated that the polymers underwent degradation through the weak-links scission. The thermal stability of the polysulfide polymers decreased as the ``rank'' (number of sulfur atoms in the polysulfide linkage; n=1, 2, 4) increased. The main-chain flexibility of these polysulfide polymers in terms of their C-13 NMR spinlattice relaxation time (T-1) measurements on the backbone methine (-CH-) and methylene (-CH2-) carbons are reported here for the first time. A comparative study of the solution chain dynamics indicated that it increased as ``rank'' of the polysulfide linkages decreased as well as by introducing side chain spacers such as, ether (-O-) or methyleneoxy (-CH2O-) groups.

Modeling of Freezing Phenomena Induced by Chemical Reactions

Spatial variations in the concentration of a reactive solute in solution are often encountered in a catalyst particle, and this leads to variation in the freezing point of the solution. Depending on the operating temperature, this can result in freezing of the solvent oil a portion of catalyst, rendering that part of the active area ineffective Freezing call occur by formation of a sharp front or it mush that separates the solid and fluid phases. In this paper, we model the extent of reduction in the active area due to freezing. Assuming that the freezing point decreases linearly with solute concentration, conditions for freezing to occur have been derived. At steady state, the ineffective fraction of catalyst pellet is found to be the same irrespective of the mode of freezing. Progress of freezing is determined by both the heat of reaction and the latent heat of fusion Unlike in freezing of alloys where the latter plays a dominant role, the exothermicity of the reaction has a significant effect on freezing in the presence of chemical reactions. A dimensionless group analogous to the Stefan number could be defined to capture the combined effect of both of these.

Formation of an unusual copper(II) complex from the degradation of a novel tricopper(II) carbohydrazone complex

An unusual copper(II) complex [Cu(L-1a)(2)Cl-2] CH3OH center dot H2O center dot H3O+Cl- (1a) was isolated from a solution of a novel tricopper(II) complex [Cu-3(HL1)Cl-2]Cl-3 center dot 2H(2)O (1) in methanol. where L-1a is 3-(2-pyridyl)triazolo [1,5-a]-pyridine, and characterized with single crystal X-ray diffraction study. The tricopper(II) complex of potential ligand 1,5-bis(di-2-pyridyl ketone) carbohydrazone (H2L1) was synthesized and physicochemically characterized, while the formation of the complex la was followed by time-dependant monitoring of the UV-visible spectra. which reveals degradation of ligand backbone as intensity loss of bands corresponding to O -> Cu(II) charge transfer.

LbL Fabricated Poly(Styrene Sulfonate)/TiO2 Multilayer Thin Films for Environmental Applications

Fabrication of multilayer ultrathin composite films composed of nanosized titanium dioxide particles (P25, Degussa) and polyelectrolytes (PELs), such as poly(allyl amine hydrochloride) (PAH) and poly(styrene sulfonate sodium salt) (PSS), on glass substrates using the layer-by-layer (LbL) assembly technique and its potentia application for the photodegradation of rhodamine B under ultraviolet (UV) irradiation has been reported. The polyelectrolytes and TiO2 were deposited on glass substrates at pH 2.5 and the growth of the multilayers was studied using UV/vis speccrophotometer. Thicknes measurements of the films showed a linear increase in film thickness with increase in number of bilayers. The surface microstructure of the thin films was characterized by field emission scanning electron microscope. The ability of the catalysts immobilized by this technique was compared with TiO2 films prepared by drop casting and spin coating methods. Comparison has been made in terms of film stability and photodegradation of rhodamine B. Process variables such as the effect of surface area of the multilayers, umber of bilayers, and initial dye concentration on photodegradation of rhodamine B were studied. Degradation efficiency increased with increase in number of catalysts (total surface area) and bilayers. Kinetics analysis indicated that the photodegradation rates follow first order kinetics. Under maximum loading of TiO2, with five catalyst slides having 20 bilayers of polyelectrolyte/TiO2 on each, 100 mL of 10 mg/L dye solution could be degraded completely in 4 h. The same slides could be reused with the same efficiency for several cycles. This study demonstrates that nanoparticles can be used in wastewater treatment using a simple immobilization technique. This makes the process an attractive option for scale up.

Adsorption-desorption and photocatalytic properties of inorganic-organic hybrid cadmium thiosulfate compounds

Three inorganic-organic hybrid framework cadmium thiosulfate phases have been investigated for adsorption and photodegradation of organic dye molecules. Different classes of organic dyes, viz., triaryl methane, azo, xanthene, anthraquinone, have been studied. The anionic dyes with sulfonate groups appear to readily adsorb on the cadmium thiosulfate compounds in an aqueous medium. The adsorption of the dye molecules, however, does not create any structural changes on the cadmium thiosulfate compounds, though weak electronic interactions have been observed. The adsorbed dyes have been desorbed partially in an alcoholic medium, suggesting possible applications in scavenging specific anionic dyes from the aqueous solutions. Langmuir adsorption/desorption isotherms have been used to model this behavior. UV-assisted (lambda(max) = 365 nm) photocatalytic decomposition studies on the cationic dyes indicate reasonable activity comparable with that of Degussa P-25 (TiO2) catalyst. Sunlight assisted photocatalyti studies have been carried out in detail employing hybrid framework compounds. The Langmuir-Hinshelwood kinetics model, employed to follow the degradation profile of the organic dyes, indicates that the photocatalytic degradation follows the order: triaryl methane > azo > xanthene.

Surfactant-Mediated Synthesis of Functional Metal Oxide Nanostructures Via Microwave Irradiation-Assisted Chemical Synthesis

In the present work we report a rapid microwave irradiation-assisted chemical synthesis technique for the growth of nanoparticles, nanorods, and nanotubes of a variety of metal oxides in the presence of an appropriate surfactant (cationic, anionic, non ionic and polymeric), without the use of any templates. The method is simple, inexpensive, and helps one to prepare nanostructures in quick time, measured in seconds and minutes. This method has been applied successfully to synthesize nanostructures of a variety of binary and ternary metal oxides such as ZnO, CdO, Fe2O3, CuO, Ga2O3, Gd2O3, ZnFe2O4, etc. There is an observed variation in the morphology of the nanostructures with changes in different process parameters, such as microwave power, irradiation time, identity of solvent, type of surfactant, and its concentration.

H N.M.R. studies of protected alpha-aminoisobutyric acid containing peptides. Chemical shift nonequivalence of benzyloxycarbonyl methylene protons

The benzylic methylene protons in a large number of benzyloxycarbonyl alpha-aminoisobutyric acid (Z-Aib) containing peptides, show chemical shift nonequivalence. The magnitude of the geminal nonequivalence is correlated with the involvement of the urethane carbonyl group, in an intramolecular hydrogen bond. Studies of the model compounds Z-Aib-Aib-Ala-NHMe, and Z-Aib-Aib-Aib-Pro-OMe clearly establish the presence of intramolecular hydrogen bonds, involving the urethane CO group. In both compounds marked anisochrony of the benzylic methylene protons is demonstrated. In Z-Aib-Aib-Pro-OMe, where a 4 leads to 1 hydrogen bonded beta-turn is not possible, the benzylic-CH2-protons appear as a singlet in CDCl3 and have a very small chemical shift difference in (CD3)2SO. The observation of such nonequivalence is of value in establishing whether the amino terminal Aib-Pro beta-turn is retained in large peptide-fragments of alamethicin.