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101.
K. Peng A. J. W. G. Visser A. van Hoek C. J. A. M. Wolfs J. C. Sanders M. A. Hemminga 《European biophysics journal : EBJ》1990,18(5):277-283
Fluorescent probes located in heterogeneous environments give rise to anomalous time-resolved fluorescence anisotropy. A simple analytical expression of anisotropy has been derived for the case of a small difference in local fluorescence lifetimes. The expression has the diagnostic advantage that the time dependence of the fluorescence anisotropy can be predicted from the differences in fluorescence lifetimes and residual anisotropies of the probes located in different sites. Using this model, the local fluorescence anisotropy parameters and the relative contributions of the lipid probe octadecyl rhodamine B in a lipid environment and in the vicinity of bacteriophage M13 coat protein reconstituted in phospholipid bilayers, composed of 80% 1,2-dimyristoyl-sn-glycero-3-phosphocholine and 20% 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol have been determined experimentally. At 40°C, the correlation times for bound and free probes are 2.3 and 3.0 ns, respectively, while the corresponding order parameters are 0.85 and 0.62, respectively.Abbreviations ESR
electron spin resonance
- DMPC
1,2-dimyristoyl-sn-glycero-3-phosphocholine
- DMPC
1,2-dimyristoyl-sn-glycero-3-phosphoglycerol
- L/P ratio
phospholipid to coat protein molar ratio
- <>
average fluorescence lifetime
-
r(0)
initial anisotropy
-
r()
residual anisotropy
On leave of Shanghai Medical Equipment Research Institute, 77 Jiang Ning Rd. Shanghai, People's Republic of China
Offprint requests to: M. A. Hemminga 相似文献
102.
Graham W. Burton Keith U. Ingold Kevin H. Cheeseman Trevor F. Slater 《Free radical research》1990,11(1):99-107
-Tocopherol, a superior chain-breaking, peroxyl radical-trapping antioxidant and the most active component of vitamin E, is elevated in liver tumor cells, contributing to their greater resistance towards lipid peroxidation compared to cells from normal tissues. Also, in regenerating rat liver the level of vitamin E has been found to fluctuate in phase with the rate of cell division. In order to study the biokinetcis and mechanisms of the distribution of vitamin E in organs and within tissues of animals, deuterated forms of -tocopherol have been synthesized and their uptake into blood and tissues has been measured by gas chromatography-mass spectrometry. Measurement of the competitive uptake from a mixture of the RRR-and SRR--tocopherol stereoisomers labelled with different amounts of deuterium shows that the liver exerts a strong preference for secretion of the natural (RRR) stereoisomer into the plasma. It is suggested that a tocopherol-binding protein plays a key role in this process. 相似文献
103.
Abstract The global regulators agr and sar control expression of cell wall and extracellular proteins. Inactivation of either sar and/or agr in a typical heterogeneously methicillin-resistant Staphylococcus aureus resulted in a small but reproducible decrease in the number of cells in the subpopulation expressing high methicillin resistance. The amount of low affinity penicillin-binding protein PBP2', the prerequisite for methicillin resistance, was apparently not affected, however, a reduction in PBP1 and PBP3 production was observed, suggesting that these resident PBPs of the cells might be involved somehow together with PBP2' in high level methicillin resistance. 相似文献
104.
The time dependence of the human
1-antitrypsin polymerization process was studied by means of the intrinsic fluorescence stopped-flow technique as well as the fluorescence-quenching-resolved spectra (FQRS) method and native PAGE. The polymerization was induced by mild denaturing conditions (1 M GuHCl) and temperature. The data show that the dimer formation reaction under mild conditions was followed by an increase of fluorescence intensity. This phenomenon is highly temperature sensitive. The structure of
1-antitrypsin dimer resembles the conformation of antithrombin III dimer. In the presence of the denaturant the polymerization process is mainly limited to the dimer state. The
1-antitrypsin activity measurements confirm monomer-to-dimer transition under these conditions. These results are in contrast to the polymerization process induced by temperature, where the dimer state is an intermediate step leading to long-chain polymers. On the basis of stopped-flow and electrophoretic data it is suggested that both C-sheet as well as A-sheet mechanisms contribute to the polymerization process under mild conditions.Abbreviations GuHCL
guanidinium hydrochloride
- RSL
reactive site loop
- PAI-1
plasminogen activator inhibitor type 1
- AT III
antithrombin III
- FQRS
fluorescence quenching resolved spectra 相似文献
105.
The contribution of the alternative pathway to the respiration of suspension-cultured pear ( Pyrus communis cv. Passa Crasanne) cells was enhanced, often severalfold, within 2 to 4 days following the addition of cycloheximide, actinomycin D, or 2-(4-methyl-2,6-dinitroanalino)- N -methyl propionamide (D-MDMP). Concomitant inhibition of cellular protein synthesis by cycloheximide and actinomycin D was transient and incomplete. However, inhibition by D-MDMP was virtually complete (>97%) and persisted over several days. [35 S]-labelling and polyacrylamide gel separation indicated that cycloheximide precluded the appearance of discernable new proteins in mitochondria. Probes with monoclonal antibodies revealed a conservation of alternative oxidase protein levels in the mitochondria of inhibitor-treated cells. The data, appraised within the complexities of cell-culture dynamics, lead to the conclusion that the observed increases in capacity for cyanide-resistant respiration are the consequence, likely indirect, of inhibited protein synthesis with resultant retention and activation of constitutive alternative oxidase. 相似文献
106.
107.
Shinichiro Nakamura Wijit Kiatipattanasakul Hiroyuki Nakayama Fumiko Ono Ippei Sakakibara Yasuhiro Yoshikawa Naoaki Goto Kunio Doi 《Journal of medical primatology》1996,25(4):294-300
Abstract: In this study, we immunohistochemically examined the several constituents of senile plaques (SPs) and cerebral amyloid angiopathy (CAA) in aged cynomolgus monkeys. Apolipoprotein E (apoE) deposited in all mature plaques and CAA, and in half of the diffuse plaques. Alpha-1-antichymotripsin (αACT) deposited in half of the mature plaques and in one third of the CAA. Amyloid precursor protein (APP), ubiquitin (Ub), and microtubule-associated protein-2 (MAP-2) accumulated in the swollen neurites of mature plaques. Glial fibrillary acidic protein (GFAP) was detected in the astrocytes and their processes surrounding the mature plaques. Tau was detected in neither the SPs nor CAA. Therefore, mature plaques involved extracellular Aβ, apoE, and αACT, and also astrocytes and swollen neurites. However, diffuse plaques involved only extracellular Aβ and apoE. Since these features, except for tau, were consistent with those in humans, this animal model will be useful for studying the pathogenesis of cerebral amyloid deposition. 相似文献
108.
Tenshuk A. Kadima Susan E. Jensen Michael A. Pickard 《Journal of industrial microbiology & biotechnology》1995,14(1):35-40
Summary -(l--Aminoadipyl)-l-cysteinyl-d-valine (ACV)-synthetase fromStreptomyces clavuligerus was studied under conditions that enabled the reuse of the enzyme. Coupling of ACV-synthetase to DEAE-Trisacryl and aminopropyl-glass resulted in an immobilized enzyme product of little or no catalytic activity. However, an enzyme reactor was designed by physical confinement of partially-purified ACV-synthetase in an ultrafiltration cell. This system was stimulated by phosphoenolpyruvate at lower concentrations of ATP, an effect not observed with purified enzyme. Up to 30% conversion of the limiting substrate, cysteine, to ACV occurred under semi-continuous conditions. Reaction products were investigated as potential inhibitors: AMP was the most inhibitory, but only when used at concentrations in excess of those produced in reaction mixtures. Under a nitrogen atmosphere, both product and enzyme stabilities were greatly improved and the enzyme retained 45–46% of its initial activity after five uses at room temperature during a 24-h period. Extrapolations based on these data suggest that 1.3 g partially purified enzyme (0.13 U g–1) would be capable of producing 411 mg of ACV in a 1-L reaction mixture in this period. 相似文献
109.
L-亮氨酸Schiff碱Cu(Ⅱ)、Ni(Ⅱ)配合物的合成及抑菌活性 总被引:2,自引:0,他引:2
合成了L-亮氨酸Schiff碱的Cu(Ⅱ)、Ni(Ⅱ)配合物,其化学结构由红外光谱、元素分析、热重分析及摩尔电导等证实。对配合物进行了抑菌测试。 相似文献
110.
利用人粒细胞集落刺激因子(hG-CSF)cDNA3′端非翻译区(3′-UTR)中存在的DraⅠ酶切位点,通过部分酶切与完全酶切,删除3′-UTR不同长度,构建了四种hG-CSFcDNA瞬时重组表达质粒。转染COS-7细胞后,生物活性测定结果提示,hG-CSFcDNA3′-UTR对其表达起负调控作用,其关键性序列位于紧接终止密码子TGA下游的65bp范围内,3′-UTR对hG-CSFcDNA表达的影响与转录水平的差别有一定关系。 相似文献