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51.
52.
Darja Fer
ej-Temeljotov Matev Kmet Darko Kocjan Sonja Kotnik Aleksander Resman Uro Urleb Katarina Verhnjak Igor Zver Janko
mitek 《Chirality》1993,5(4):288-292
Structure–interaction relationships, stereoselectivity, and solubility enhancement in inclusion compexation of β-cyclodextrins (CDs) with some racemic and enantiomerically pure 1,4-dihydropyridine derivatives (DHPs) were investigated. 1:1 and 1:2 (mole ratio) complexes were prepared and characterized by X-ray powder diffraction, differential scanning calorimetry (DSC), MS-FAB spectrometry, 1H-NMR spectroscopy, water and phase solubility. The solubility studies have revealed different complexation equilibria for optically pure DHP enantiomers, and corresponding racemic mixtures in water solutions. By means of 1H-NMR chemical shift measurements, the inclusion of aromatic fragments of racemic and enantiomerically pure DHP molecules within the cavities of different CDs was elucidated. Considerable stereoselectivity in complexation interactions was observed. The results indicate the potential use of cyclodextrins as chiral selectors for enantiomeric resolution of 1,4-DHP calcium antagonists. © 1993 Wiley-Liss, Inc. 相似文献
53.
Human papilloma virus E6/E7 genes can expand the lifespan of human corneal fibroblasts 总被引:2,自引:0,他引:2
Donna M. Peters Nathan Dowd Curtis Brandt Teresa Compton 《In vitro cellular & developmental biology. Animal》1996,32(5):279-284
Summary Human corneal fibroblasts were infected with a retroviral delivery vector containing the E6 and E7 genes from human Papilloma
virus type 16 in order to produce cell lines that have an expanded lifespan in culture. Morphologically, some of the trasfected
corneal fibroblast lines appeared to have the normal spindle-shape morphology of diploid fibroblasts, whereas other lines
appeared to have a more elongated morphology. All the cell lines were anchorage-dependent. Cells that had a normal morphology
grew at a rate similar to normal diploid human corneal fibroblasts and had a population doubling time of 48 h. All E6/E7 expressing
cell lines, regardless of morphology, produce types I, III, and V collagen, at levels similar to those observed in the parent
corneal diploid fibroblast. These corneal fibroblast lines will be a usefulin vitro system to study collagen expression and fibril formation, as well as normal stroma development. These results also demonstrate
that the use of E6/E7 genes to expand a cell’s lifespan can be a powerful tool because it does not appear to alter either
the growth rate of the cell or collagen expression. 相似文献
54.
Jeanette Møller Nielsen Jürgen Hansen Kirsten Brandt 《Plant Cell, Tissue and Organ Culture》1995,41(2):165-170
Shoots of Miscanthus X ogiformis Honda Giganteus transferred from medium with benzyladenine (BA) to thidiazuron (TDZ) formed significantly more axillary shoots than shoots grown continuously on either medium, or transferred from TDZ to BA. Shoot formation on axillary shoots transferred from BA-containing media to media with kinetin or isopentenyladenine (2iP) or transferred from media with TDZ, kinetin or 2iP to media with BA, corresponded to the number of shoots formed in the previous subculture. Shoot formation on shoots transferred from medium containing BA to media containing combinations of BA and/or TDZ increased with increasing concentrations of TDZ in the first subculture, whereas shoot formation in the second and third subculture depended on the BA concentration. When shoots were transferred from media with BA to media with TDZ, the time for shoot formation, as well as shoot size, indicate that the combined effect of BA and TDZ is expressed only during the early phase of the subculture. The results suggest that adenine- and phenylurea-type cytokinins have a common binding site in the plant cell, and a model is proposed.Abbreviations BA
6-benzyladenine
- CBP
cytokinin-binding protein
- 2iP
isopentenyladenine
- KIN
kinetin
- MS
Murashige & Skoog
- TDZ
thidiazuron 相似文献
55.
Gas-vesicle (Vac) synthesis in Halobacterium salinarium PHH1 involves the expression of the p-vac region consisting of 14 different gvp genes that are arranged in two clusters: p-gvpACNO and, oppositely oriented, p-gvpDEFGHIJKLM. The latter cluster of genes is transcribed as two units: p-gvpDE and p-gvpF–M. The 5′-terminus of the p-gvpF–M mRMA was located 169 nucleotides upstream of p-gvpF within p-gvpE. The p-gvpG and p-gvpK gene was expressed in Escherichia coli and antibodies to proteins obtained were raised in rabbits. Both proteins could be detected in halobacterial cell lysates; in gas-vesicle preparations, however, neither GvpG nor GvpK could be found. The requirement for single p-gvp gene expression for gas-vesicle synthesis was determined by transformation experiments using the Vac? species Haloferax volcanii as recipient. Construct ΔA containing all p-gvp genes except for p-gvpA, encoding the major gas-vesicle structural protein, produced Vac? transformants, but the addition of p-gvpA on a second vector restored gas-vesicle synthesis to wild-type level (Vac++). Similarly, double transformants containing p-gvpD–M plus p-gvpACNO, or p-gvpG–M (fused to the promoter of the halobacterial ferredoxin gene for expression) plus p-gvpFED–ACNO were Vac++. Transformants containing the p-vac region either lacking gvpA, gvpF, or gvpGHI were Vac?, indicating the absolute requirement of these gvp genes (or at least one in the case of gvpGHI) for gas-vesicle formation. Double transformants containing the constructs p-gvpF–M plus p-gvpACNO (ΔDE) accumulated gas vesicles (Vac+) but synthesized fewer than the wild type, showing that the p-gvpDE genes are not necessary for gas-vesicle assembly. A repressor function affecting the synthesis of the p-gvpF–M mRNA could be suggested for p-gvpD and the 5′- region of its mRNA. 相似文献
56.
R N Cox R R Kaldany P W Brandt B Ferren R A Hudson A Karlin 《Analytical biochemistry》1984,136(2):476-486
A continuous-flow technique is described in which a photoaffinity label, membrane rich in acetylcholine receptor, and various effectors are rapidly mixed, passed through a delay tube, through a tube in which they are irradiated, and are collected in a tube containing quencher. Delay times as short as 20 ms between mixing and photolysis are achievable. Because the flow is continuous, milliliter volumes of membrane can be labeled in a single run, which is convenient for the analysis of both the functional effects and sites of photolabeling. Using this technique, we have found that receptor in its transitory, active state, in which the channel is open, is more susceptible to photolabeling by the noncompetitive inhibitor analog [3H] quinacrine azide than is receptor in either its resting or desensitized states, in which the channel is closed. This technique should prove generally useful for the photolabeling of transient conformational states of macromolecules. 相似文献
57.
D- and L-lactate catabolism to CO2 in rat tissues 总被引:1,自引:0,他引:1
R B Brandt M G Waters M J Rispler E S Kline 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1984,175(3):328-335
The current study was initiated in order to compare the rates of oxidative catabolism of D- and L-lactate in various rat tissues. Uniformly labeled D- or L-[14C]lactate was incubated at 37 degrees C in a closed system with tissue homogenates in Krebs-Ringer phosphate buffer. Evolved 14CO2 was trapped in a center well containing a fluted filter paper saturated with strong base and the radioactivity determined. The ratio of L-lactate to D-lactate oxidation was greatest in brain, followed by kidney, heart, and liver. In liver the rate of oxidation of D-lactate exceeded that of L-lactate, in heart the rates were not significantly different and in the other two tissues L-lactate was oxidized more rapidly than D-lactate. These results indicate that the rate of D-lactate catabolism is considerable and is relatively greater than had been reported previously. 相似文献
58.
59.
The prokaryote Cyanocyta korschikoffiana was isolated from the eukaryote Cyanophora paradoxa. The synthesis of several thylakoid proteins in these cyanelles is influenced by light and darkness and is sensitive to cycloheximide, the inhibitor of the eukaryotic host's translation. The possibility of a direct coordination between the translations of the host and of the cyanelles is discussed.Abbreviations CHM treatment
addition of cycloheximide
- CPN
chlorophylline
- PBN
phycobiline
- SDS-PAGE
sodium-dodecylsulphate-polyacrylamide gelelectrophoresis 相似文献
60.
Summary A saturator of small dimensions is described. Moist air with dewpoint temperatures ranging from 2°C to 30°C with a long-term stability of ±0.05°C and a maximum output of 400 1/h can be attained.Special attention is paid to the calibration procedure and to the effect of the reduction of dewpoint temperature of moist air flowing through a tube. 相似文献