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1.
2.
A phospholipid, 1,2-bis(4-(n-butyl)phenylazo-4'-phenylbutyroyl)phosphatidylcholine (Bis-Azo PC), has been synthesised and shown to form stable bilayer vesicles. Light-scattering measurements and differential scanning calorimetry show that a dispersion of the lipid has a cooperative phase transition at a similar temperature to that of dipalmitoylphosphatidylcholine, which Bis-Azo PC resembles in overall size. The phase behaviour of Bis-Azo PC has been investigated by fluorescence spectroscopy and using a series of spin-labelled fatty acid probes. Fluorescence measurements using chlorophyll a as probe sense the onset of the cooperative phase transition, but this is not clearly revealed by any of the spin probes tested. Hysteresis in the phase transition is detected both by light scattering measurements and by fluorescence spectroscopy. No transition is observed for a lipid analogue having a palmitic acid chain and a single azo-containing substituent. Bis-Azo PC is reversibly photochromic, isomerising on exposure to ultraviolet light to a photostationary state mixture where cis isomer predominates. Electron microscopy shows that photoisomerisation decreases average vesicle size, and light scattering and calorimetry demonstrate that the cooperative phase transition is abolished. Illumination with visible light establishes a new photostationary state where trans isomer predominates, and the phase transition is restored. The ability to modulate bilayer phase behaviour reversibly has possible application to relaxation studies of bilayer membrane function, and to drug delivery research. 相似文献
3.
Fluorescence studies of Hoechst 33342 with supercoiled and relaxed plasmid pBR322 DNA 总被引:1,自引:0,他引:1
The fluorescence properties of Hoechst 33342 (HO 33342) were examined with plasmid pBR322 in the supercoiled (Form I) or relaxed covalently closed circular (Form Io) conformation in order to determine whether qualitative or quantitative differences in fluorescence properties might provide an assay for topological states of DNA. It was found that HO 33342 exhibited a 30% greater fluorescence intensity with Form I pBR322, independent of the dye or DNA concentration. As the dye to DNA ratio was increased, a red shift of approximately 8 nm was observed for HO 33342 complexed with Form I or Form Io. The red shift in fluorescence emission occurred at higher HO 33342 concentrations with Form I vs. Form Io DNA; however, when Form I and Form Io were mixed in various proportions, neither the fluorescent intensity differences nor the HO 33342 concentration at which the wavelength shift occurred could be used to quantitate the relative proportions of topological states present. These results suggest that although the fluorescence properties of HO 33342 complexed with Form I DNA are different than those of HO 33342 complexed with Form Io DNA, the fluorescence assay is not sufficiently sensitive to quantitatively discriminate among a mixture of DNA in various topological states. 相似文献
4.
Thirteen yeast species belonging to nine genera were screened for the production of single-cell protein (SCP) using cheese whey as the substrate. Cheese whey supplemented with minerals and yeast extract proved to the best medium for yield, lactose utilization, biomass production, and conversion efficiency. Production of beta-galactosidase was studied in Brettanomyces anomalus, Kluyveromyces fragilis, Trichosporon cutaneum, and Wingea robertsii; the last proved to be the best strain combining high yield with shorter incubation period. 相似文献
5.
The pathogenicity ofNocardia caviae, N. asteroides andN. brasiliensis has been tested for white mice, guinea pigs and rabbits and chorio-allantoic membrane of the developing chick embryo. Altogether, 14 strains belonging to the 3Nocardia species originating from soil, human and animal sources in India or abroad were tested. All of them proved pathogenic though the degree of virulence varied from strain to strain. Incorporation of hog gastric mucin in the inoculum enhanced the virulence of all the 3Nocardia species for white mice.N. caviae strains were uniformly more virulent than those ofN. asteroides andN. brasiliensis.In the white mice inoculated intraperitoneally, a greater dissemination of the disease was apparent withN. caviae than withN. asteroides. Of the 6 strains ofN. caviae tested, 5 disseminated to the lung, 3 to the heart and 2 to the brain. InN. asteroides dissemination of the disease to the brain was observed with 2 of its 3 strains.N. brasiliensis showed no dissemination.N. caviae was found to be equally virulent for white mice, guinea pigs and rabbits. On the other hand,N. asteroides andN. brasiliensis were more virulent for white mice than for guinea pigs and rabbits. The lesions caused byN. caviae in mice, guinea pigs and rabbits persisted up to 4 weeks. In strong contrast to this the lesions due toN. asteroides andN. brasiliensis found in the guinea pigs and rabbits showed a strong tendency towards spontaneous clearance.Histologically, the lesions caused byN. caviae, N. asteroides andN. brasiliensis in mice, guinea pigs and rabbits were in the form of abscesses which showed an acute or chronic reaction. In the case ofN. caviae these abscesses showed both granules and freely dispersed cocco-bacillary bodies or filaments. As forN. asteroides it occurred in the form of cocco-bacillary bodies or filaments whereasN. brasiliensis consistently produced granules in the lesions.The lesions caused by the 3Nocardia species on the chorio-allantoic membrane of the developing chick embryo were in the form of abscesses which contained cocco-bacillary bodies and branching filaments but no granules.This forms a part of the thesis submitted by P.V.K. for Ph. D. degree, of the University of Delhi. 相似文献
6.
Current proposals in the general practitioner contract include additional payments to doctors working among deprived populations. The underprivileged area score will be used to identify local authority wards with the greatest levels of deprivation, thus acting as the basis for distributing considerable resources. Two methods of identifying deprived populations--the underprivileged area score and the material deprivation score--were compared to determine whether they result in similar allocation of resources to regions. Financial allocations to regions based on figures derived from the contract differed considerably if the material deprivation score was used instead of the underprivileged area score: Northern and Mersey regions gained over 50% of their allocation whereas East Anglia, Oxford, and South West Thames regions lost more than 30% of theirs. Such differences have considerable implications for doctors working among deprived populations as up to 60m pounds each year might be distributed by these payments. 相似文献
7.
S. K. Soni I. K. Sandhu K. S. Bath U. C. Banerjee P. R. Patnaik 《Folia microbiologica》1996,41(3):243-248
A strain of starch-assimilating yeast,Saccharomycopsis capsularis, isolated from Indian cereal-based fermented foods, produced significant levels of extracellular α-amylase and glucoamylase.
The enzymes reached their peak activities during the stationary phase at the end of the 5th and 4th day of cultivation, respectively.
The amylase yields were maximized by a proper choice of carbon and nitrogen sources, starting pH of the culture medium and
growth temperature. High activities of the enzymes were obtained through inexpensive agricultural commodities, such as wheat
bran and corn meal as carbon sources, and defatted soybean meal and peanut meal as nitrogen sources. A temperature of 28–32°C
and an initial pH of 4.5–5.0 were optimum. The crude amylase mixture could liquefy and saccharify a 1% starch solution completely
in 24 h at 50°C. 相似文献
8.
9.
Unformulated conidia of Beauveria bassiana were stored at five different temperatures (0°, 10°, 20°, 30° and 40°C) at six different relative humidities (RH) (0, 33, 53, 75, 85 and 98%). Conidial viabilities and virulence against third instar larvae of Helicoverpa armigera were determined over a 24‐month period. Conidia survived longest at lower temperatures (0–20°C) and lower RH levels (0–53% RH). At higher temperatures (30–40°C) conidia did not survive. When the temperature was decreased from 30°C to 0°C, at nearly all RH levels the longevity of conidia increased. Conidia remained virulent for third instar larvae of H. armigera under favourable storage conditions for 24 months. 相似文献
10.
Allergic bronchopulmonary aspergillosis (ABPA): Studies on the general and specific humoral response
Serum specimens from 138 patients suffering from chronic respiratory disorders including 63 with allergic bronchopulmonary aspergillosis (ABPA), 20 with suspected ABPA, 25 with pulmonary tuberculosis, 14 with bronchial asthma, 10 with chronic bronchitis and 6 with miscellaneous pulmonary conditions were studied for circulating antibodies to Aspergillus. The ammonium sulfate test was employed with an iodine-125 labeled mycelial component derived from Aspergillus fumigatus. When compared to normal controls from the same area, this test indicated that sera from 82 per cent of patients with ABPA had elevated binding titers to the radiolabeled antigenic component. Immunodiffusion using a culture filtrate antigen from A. fumigatus, revealed precipitating antibody to this fungus in 89 per cent of sera from ABPA patients. The majority of patients with ABPA demonstrated marked elevations of total serum IgE, moderate elevations of serum IgA and IgD and slightly increased levels of IgG and IgM.This study was supported in part by Research Grant AI 10940 from the National Institutes of Health and by NHLI Contract N01-HL-3-2942(B), and forms a part of the Ph.D. thesis submitted by Z.U.K. to the University of Delhi. 相似文献