Showing papers by "National Chemical Laboratory published in 1993"
TL;DR: The proteolytic activity produced by aBacillus subtilis isolated from a hot spring was investigated and effects of various carbon and nitrogen sources indicate the requirement of starch and bacteriological peptone to be the best inducers for maximum protease production.
Abstract: The proteolytic activity produced by a Bacillus subtilis isolated from a hot spring was investigated. Maximum protease production was obtained after 38 h of fermentation. Effects of various carbon and nitrogen sources indicate the requirement of starch and bacteriological peptone to be the best inducers for maximum protease production. Requirement for phosphorus was very evident, and the protease was secreted over a wide range of pH 5-11. The partially purified enzyme was stable at 60 degrees C for 30 min. Calcium ions were effective in stabilizing the enzyme, especially at higher temperature. The enzyme was extremely salt tolerant and retained 100% activity in 5M NaCl over 96 h. The molecular weight of the purified enzymes as determined by SDS-PAGE was 28,000. The enzyme was completely inactivated by PMSF, but little affected by urea, sodium dodecyl sulfate, and sodium tripoly phosphate.
329 citations
TL;DR: An analysis of the binding of 52 sulfate and phosphate ions in 34 protein structures has been carried out, finding patterns in the binary and ternary interactions involving various anions.
195 citations
TL;DR: Its stability over a range of alkaline pH and temperature and its compatibility with commercial detergents was determined, and the enzyme was most stable between pH 6.0–8.5 and at temperatures up to 40°C.
192 citations
TL;DR: Results indicate that nucleotide sequences are conserved, but variation in copy number were detected and several rearrangements in linkage orders appeared to have occurred since the divergence of the two species.
Abstract: Genome relationships between mungbean (Vigna tradiata) and cowpea (V. Unguiculata) based on the linkage arrangement of random genomic restriction fragment length polymorphism (RFLP) markers have been investigated. A common set of probes derived from cowpea, common bean (Phaseolus vulgaris), mungbean, and soybean (Glycine max) PstI genomic libraries were used to construct the genetic linkage maps. In both species, a single F2 population from a cross between an improved cultivar and a putative wild progenitor species was used to follow the segregation of the RFLP markers. Approximately 90% of the probes hybridized to both mungbean and cowpea DNA, indicating a high degree of similarity in the nucleotide sequences among these species. A higher level of polymorphism was detected in the mungbean population (75.7%) than in the cowpea population (41.2%). Loci exhibiting duplications, null phenotypes, and distorted segregation ratios were detected in both populations. Random genomic DNA RFLP loci account for about 89% of the currently mapped markers with a few cDNA and RAPD markers added. The current mungbean map is comprised of 171 loci/loci clusters distributed in 14 linkage groups spanning a total of 1570cM. On the other hand, 97 markers covered 684 cM and defined 10 linkage groups in the current cowpea map. The mungbean and cowpea genomes were compared on the basis of the copy number and linkage arrangement of 53 markers mapped in common between the two species. Results indicate that nucleotide sequences are conserved, but variation in copy number were detected and several rearrangements in linkage orders appeared to have occurred since the divergence of the two species. Entire linkage groups were not conserved, but several large linkage blocks were maintained in both genomes.
144 citations
TL;DR: The staining pattern indicates that the trkB-like antigen is widely distributed and present within both glia and neurons, aiding the definition of neuronal and glial subpopulations of the central nervous system that may utilize BDNF.
100 citations
TL;DR: The contribution chitin enzymology can make to basic and applied research is discussed and applications in ultrastructural studies, in the preparation of chitooligosaccharides which show anti-tumour activity, as biocontrol agents and in single-cell protein production are discussed.
Abstract: After cellulose, chitin is the second most abundant renewable resource available in nature. Marine invertebrates and fungal biomass are the two main sources of chitinous waste, which is commercially exploited. The enzymes involved in chitin degradation have been particularly well studied. Such enzymes have applications in ultrastructural studies, in the preparation of chitooligosaccharides which show anti-tumour activity, as biocontrol agents and in single-cell protein production. Here, the contribution chitin enzymology can make to basic and applied research is discussed.
95 citations
TL;DR: In this article, the vapour phase hydrogenation of phenol over platinum and palladium supported on alumina and zeolite LTL was studied in a vertical fixed-bed high-pressure reactor.
Abstract: The vapour-phase hydrogenation of phenol over platinum and palladium supported on alumina and zeolite LTL was studied in a vertical fixed-bed high-pressure reactor. The major products of the hydrogenation reaction were cyclohexanone and cyclohexanol with cyclohexane, cyclohexene and benzene as the minor products. The selectivity for the major products was upto 99%, the conversion being influenced by temperature, feed rate and the partial pressure of hydrogen. Platinum catalysts were found to be better for the production of cyclohexanol while palladium catalysts favoured cyclohexanone production. The platinum catalysts also showed twice as much overall conversion as the palladium catalysts.
90 citations
TL;DR: The results indicate that putative partial resistance loci for powdery mildew in mungbean can be identified with DNA markers, even in a population of modest size analyzed at a single location in a single year.
Abstract: We have used restriction fragment length polymorphisms (RFLPs) to map genes in mungbean (Vigna radiata) that confer partial resistance to the powdery mildew fungus, Erysiphe polygoni. DNA genotypes for 145 RFLP loci spanning 1570 centimorgans of the mungbean genome were assayed in a population of 58 F2 plants. This population was derived from a cross between a moderately powdery mildew resistant (“VC3980A”) and a susceptible (“TC1966”) mungbean parent. F3 lines derived from the F2 plants were assayed in the field for powdery mildew response and the results were compared to the RFLP genotype data, thereby identifying loci associated with powdery mildew response. A total of three genomic regions were found to have an effect on powdery mildew response, together explaining 58% of the total variation. At 65 days after planting, two genomic regions were significantly associated with powdery mildew resistance. For both loci, the allele from “VC3890A” was associated with increased resistance. At 85 days, a third genomic region was also associated with powdery mildew response. For this locus, the allele from the susceptible parent (“TC1966”) was the one associated with higher levels of powdery mildew resistance. These results indicate that putative partial resistance loci for powdery mildew in mungbean can be identified with DNA markers, even in a population of modest size analyzed at a single location in a single year.
88 citations
TL;DR: In this article, the catalysts are first activated in the initial reaction, which is started at 535-560°C, by the reduction of NiO and creation of active sites.
Abstract: NiO-LnO x
(Ln = lanthanide) catalysts (with Ni∶Ln=1∶1) without prereduction show high activity/selectivity and very high productivity in the oxidative conversion of methane to CO and H2. The catalysts are first activated in the initial reaction, which is started at 535–560°C, by the reduction of NiO and creation of active sites. The carbon deposition on the catalysts in the reaction, particularly for the NiO-Gd2O3, NiO-Tb4O7 and NiO-Dy2O3 catalysts, is quite fast but it has caused a little or no influence on the catalytic activity/selectivity. Pulse reaction of pure methane on NiO-Nd2O3 (at 600°C) shows involvement of lattice oxygen in the initial reaction and also reveals formation of carbon from CO on the catalyst reduced in the reaction.
88 citations
TL;DR: In this article, the isopropylation of benzene with propene over Al-, B- and Ga-beta zeolites is reported and the influence of the SiO 2 /Al 2 O 3 ratio, space velocity, temperature and reactants mole ratios are discussed.
Abstract: The isopropylation of benzene with isopropanol/propene over Al-, B- and Ga-beta zeolites is reported. The influence of the SiO 2 /Al 2 O 3 ratio, space velocity, temperature and reactants mole ratios are discussed. The selectivity to cumene is maximum at lower SiO 2 /Al 2 O 3 ratio and at lower space velocity as well as higher benzene-to-isopropanol ratio. At higher temperatures, cumene isomerizes to n-propyl benzene. Zeolite beta does not exhibit any product shape selectivity among the di-isopropyi benzene isomers. The activity and selectivity of H-Al-beta is compared with other large pore zeolites such as Hmordenite and H-ZSM-12. The stable activity and higher selectivity over zeolite beta can be attributed to its highly silicious nature and interconnecting channel system.
84 citations
TL;DR: In this paper, the authors investigated the low-temperature sinterability of calcium-doped lanthanum chromites which are to be used as interconnectors in solid oxide fuel cells (SOFCs).
Abstract: Investigations have been made on the low-temperature sinterability of calcium-doped lanthanum chromites which are to be used as interconnectors in solid oxide fuel cells (SOFCs). Nominally chromium deficient lanthanum calcium chromites (La[sub 0.7]Ca[sub 0.3]Cr[sub 1[minus]y]O[sub 3], y = 0.02) were found to be sinterable to 94% theoretical density at 1573 K in air, whereas no densification was observed for samples with y = 0. The two-step shrinkage process suggests a liquid-phase sintering mechanism with calcium oxychromates playing an important role as the liquid phase. After sintering at 1573 K, calcium-rich substances remained at grain boundaries.
TL;DR: In this article, the authors compared the performance of TS-2 and VS-2 catalysts in the hydroxylation of phenol, and found that the oxidations are deeper on VS2 than on TS2, while the primary carbon atoms of the alkanes and the methyl substituents of the aromatic hydrocarbons of the phenol were different.
Abstract: Selective oxidation reactions like the oxyfunctionalization of alkanes, hydroxylation of aromatics and sulfoxidation of thioethers have been carried out with dilute hydrogen peroxide over titanium and vanadium metallosilicate molecular sieves with MEL topology, viz., TS-2 and VS-2. Though both the catalysts possess similar activities, substantial differences in the product distribution are observed. The oxyfunctionalization of the primary carbon atoms of the alkanes and the oxidation of the methyl substituents of the aromatic hydrocarbons distinguish VS-2 from TS-2. Both the catalysts are found to be equally active in the hydroxylation of phenol, though they possess different activities in different solvents. In general, the oxidations are “deeper” over VS-2 than on TS-2.
TL;DR: In this paper, critical examples from the last ten years dealing with the radical ion reactions of synthetic importance initiated by photoexcitation of donor-acceptor pairs are discussed. But the focus of this paper is not on the reactions of the last decade.
Abstract: PET processes between ground and excited states of donor-acceptor pairs lead to the formation of radical ion pairs which upon disproportionation gives neutral radicals and/or ions required for synthetic purposes. A host of new reactions has been uncovered, the nature of which is governed by the chemical properties and reactivity profiles of these reactive intermediates. Our objective in this chapter will be to enlist critical examples from the last ten years dealing with the radical ion reactions of synthetic importance initiated by photoexcitation of donor-acceptor pairs.
TL;DR: Surprisingly, a gene complementing the swi7 mutation maps to chromosome I and encodes S. pombe DNA polymerase-α, suggesting that DSB formation is coupled with DNA replication.
Abstract: IN the fission yeast Schizosaccharomyces pombe, the double-stranded chromosomal break (DSB) at the mating-type locus (mat1) initiates recombination during mating-type switching1–3. A constant DSB level is maintained throughout the cell-cycle1. In the strand-segregation model for mating-type switching, it was postulated that if the DSB is generated during or soon after mat1 replication4, one of the chromatids could be repaired and switched during replication in the next cell cycle, while the other chromatid inherits the break3–6. Here we report a molecular characterization of swi7, one of the genes required for DSB formation. Surprisingly, a gene complementing the swi7 mutation maps to chromosome I and encodes S. pombe DNA polymerase-α. Disruption of this gene is lethal in both switching and non-switching strains, as expected. S. pombe DNA polymerase-α must therefore play a role in generating the DSB at mat1, suggesting that DSB formation is coupled with DNA replication.
TL;DR: In this article, a gas chromatography pulse technique was used to investigate the adsorption of methane, ethane, ethylene, and carbon dioxide in HZSM-5, Na-ZSMM-5 and ALPO-5 at 303-473 K.
Abstract: Adsorption of methane, ethane, ethylene, and carbon dioxide in H-ZSM-5, Na-ZSM-5, H-ZSM-8, Na-ZSM-8, Silicalite, and ALPO-5 at 303–473 K has been investigated using a gas chromatography pulse technique. The zeolites have been compared for the heat of adsorption of the adsorbates at near zero adsorbate loading and also for the specific retention volume (or thermodynamic adsorption equilibrium constant) of ethane, ethylene, and carbon dioxide relative to that of methane. Among the zeolites, ALPO-5 has a high potential for the separation of methane, ethane, ethylene, and carbon dioxide from their mixture.
TL;DR: In this article, the thermal decomposition of n−octadecyl amine-titanyl oxalate complex multilayer Langmuir-blodgett films was used to obtain thin TiO2 films.
Abstract: Excellent quality thin TiO2 films have been obtained by the thermal decomposition of n‐octadecyl amine‐titanyl oxalate complex multilayer Langmuir–Blodgett films. The films were characterized by x‐ray diffraction and x‐ray photoemission studies. X‐ray diffraction studies suggest a preferred orientation of the TiO2 films.
TL;DR: Vanadium silicate molecular sieves with MEL structure (VS-2 ) were found to be active in the hydroxylation of phenol with hydrogen peroxide, a reaction which is commercially practiced over titanium silicalite (TS-1 and TS-2) catalysts as discussed by the authors.
Abstract: Vanadium silicate molecular sieves with MEL structure (VS-2 ) are found to be active in the hydroxylation of phenol with hydrogen peroxide, a reaction which is commercially practiced over titanium silicalite (TS-1 and TS-2) catalysts. Among various reaction parameters, the influence of the solvent on the conversion and product selectivity appears to be different from that reported on titanium silicalites. In methanol, for example, no hydroxylation takes place. In water, the phenol conversion as well as the H 2 O 2 selectivity follows the order, TS-1 > TS-2 > VS-2. Only those vanadium ions which are in the lattice positions appear to catalyse this reaction.
TL;DR: In this article, the performance and characteristics of solid acid type catalysts such as H-ZSM-5 and alumina for the title reaction were investigated and it was suggested that the oxidation of NO to NO 2 is an important reaction step in the overall NO reduction.
TL;DR: In this paper, an yttria stabilized zirconia (YSZ) membrane reactor system was applied to enhance the direct thermal decomposition of CO 2 at high temperature, and the decomposition rate of CO2 and the permeation rate of oxygen through the membrane were measured and their equations were established.
TL;DR: In this paper, the surface potential of poly(ethylene terephthalate), polyimide, and polyethersulfone films has been investigated by measuring the surfaces potential on the films and the velocity distribution in ionic fragments.
01 Jun 1993
TL;DR: In this paper, the authors reported near-selective nitration of phenol to ortho-nitrophenol using a suitably prepared microemulsion solution in the presence of dilute nitric acid.
Abstract: The paper reports near-selective nitration of phenol to ortho -nitrophenol using a suitably prepared microemulsion solution in the presence of dilute nitric acid. The case example indicates that microemulsions, besides enhancing the reaction rates, can also be selective to give the desired product. Microemulsion solution also affords the use of dilute acid as a nitrating agent.
TL;DR: In this article, the first-order kinetics equation and apparent activation energies for the processes of nucleation (En) and crystallization (Ec) were calculated by applying the Arrhenius equation.
TL;DR: In this article, the rate equation derived assuming the addition of H2 as a rate determining step, has been found to represent the data satisfactorily and the rate parameters for the mechanistic model have been evaluated for the data at 60 °C.
Abstract: The kinetics of hydroformylation of 1-decene using homogenous HRh(CO)(PPh3)3 catalyst has been reported in the temperature range of 50–70 °C. The effect of catalyst,PH2,PCO, and 1-decene concentration on the rate of hydroformylation has been studied. Based on the analysis of initial rate data, a rate equation has been proposed and kinetic parameters evaluated. The activation energy was found to be 11.76 kcal/mol. A molecular level approach to kinetic modelling has also been illustrated. The rate equation derived assuming oxidative addition of H2 as a rate determining step, has been found to represent the data satisfactorily. The rate parameters for the mechanistic model have been evaluated for the data at 60 °C.
TL;DR: In this article, a TiO3-based mixed oxide catalysts containing chromium, iron, cobalt or nickel were prepared and used in the oxidation of methane and showed high activity for the synthesis gas production from methane.
Abstract: Ca1−x
- x
Sr
x
TiO3-based mixed oxide catalysts containing chromium, iron, cobalt or nickel were prepared and used in the oxidation of methane. The catalyst containing cobalt or nickel showed high activity for the synthesis gas production from methane. In the case of nickel containing catalyst, nickel oxide originally separated from the perovskite structure was easily reduced to nickel metal, which showed synthesis gas production activity. In the case of the cobalt containing catalyst, pretreatment with methane was required for high activity. Reduced metallic cobalt was formed from the perovskite structure, which revealed relatively high selectivity for the oxidative coupling of methane, and afforded synthesis gas production. Both the catalysts also catalyzed carbon dioxide reforming of methane and especially both high activity and selectivity were observed over the nickel containing catalyst.
TL;DR: In this paper, a simple model considering primary and secondary crystallization has been proposed, which is verified using isothermal crystallization data of PPS and is shown to be a good fit only to the isothermal data of PET.
Abstract: Analysis of isothermal crystallization data of PET and PPS was carried out using Avrami and Tobin models. The models gave fractional values of exponent n and the standard deviation varied between 1 and 4%. No improvement in the standard deviation could be obtained even after incorporating the nucleation rate in these models. The Hillier model gave a good fit only to the isothermal crystallization data of PET. A simple model considering primary and secondary crystallization has been proposed. The model is verified using isothermal crystallization data of PPS. © 1993 John Wiley & Sons, Inc.
TL;DR: Koide et al. as discussed by the authors showed that deep aquifers, which are not used due to high salinity, can host larger amount of carbon dioxide under their high formation pressure than natural gas and oil reservoirs.
TL;DR: This is the first report of an extracellular fungal xylanase which is active and stable at high alkaline pH (8–9.5) and the culture filtrate did not show any significant cellulase activity.
Abstract: An alkalotolerant Cephalosporium (NCL 87.11.9) strain capable of rapid growth and xylanase secretion over a wide pH range (pH 4–10) has been isolated from soil samples. When grown in shake flasks on a wheat bran, yeast extract medium for 96 h it produced 15 to 18 IU/ml. The novel feature of this study is that it is the first report of an extracellular fungal xylanase which is active and stable at high alkaline pH (8–9.5). The culture filtrate did not show any significant cellulase activity. Gel filtration studies indicated two peaks of xylanase activities corresponding to molecular weights of 70,000 and 30,000 in the proportion of 10:90.
TL;DR: Five genotypes of chickpea (Cicer arietinum L.) PG1, PG5, PG12, N59 and C235 were evaluated for induction of somatic embryogenesis and somatic embryos derived from cotyledonary segments of genotype PG12 formed callus.
Abstract: Five genotypes of chickpea (Cicer arietinum L.) PG1, PG5, PG12, N59 and C235 were evaluated for induction of somatic embryogenesis. Somatic embryogenesis was induced from immature cotyledons of genotypes PG12 and C235 and immature embryo axes of genotypes PG5, PG12 and C235. Genotypes N59 and PG1 showed no response. The maximum frequency of globular embryo formation occurred in cotyledonary segments on MS medium with 3.0 mg/l 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Further embryo development was achieved only in somatic embryos derived from cotyledonary segments of genotype PG12. Globular-stage embryos derived from immature embryo axes of PG5, C235, PG12, and cotyledonary segments of C235 dedifferentiated and formed callus. The cotyledonary stage embryos of genotype PG12 germinated on half-strength MS medium supplemented with 1 mg/l zeatin. The regenerated plants were transferred to soil and grown to maturity.