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Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones 总被引:1,自引:1,他引:0
A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer. 相似文献
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The reversible inhibition of respiratory activity could provide a novel approach to the preservation of traditionally hard to store plant germplasm such as clonal materials and recalcitrant seed. The gaseous anesthetic nitrous oxide caused a reversible, dose-dependent, partial inhibition of dioxygen utilization in mitochondrial particles isolated from cell suspension cultures of the salt-tolerant marsh grass Distichlis spicata, with maximal inhibition of 33% after 30 minutes exposure to an atmosphere of 80% nitrous oxide plus 20% oxygen. Respiration of whole cells required longer time to be affected by the anesthetic, and was reversibly inhibited an average of 19% when measured using a differential respirometer. Exposure to 80% nitrous oxide plus 20% oxygen for up to 10 days caused no measurable effect on cell growth.Abbreviations PCV
packed cell volume
- EDTA
sodium ethylenediaminetetraacetic acid
- BSA
bovine serum albumin
- MOPS
3(N-morpholino) propanesulfonic acid
- TMPD
N,N,N',N'-tetramethyl-p-phenylene diamine
- STP
standard temperature and pressure 相似文献
7.
Leigh EG 《Trends in ecology & evolution》1991,6(8):257-262
Adam Smith proposed that individuals can share sufficient interest in their society's welfare to profit by cooperating for its benefit and by jointly suppressing behavior hurtful to it. Similarly, a genome's genes share a common interest in 'honest' meiosis, which ensures that alleles can spread only by benefitting their carriers. Honeybee workers express a common interest in raising their queen's, rather than their half-sisters', eggs by eating eggs laid by half sisters. Can analogous principles explain the evolution of harmony at other levels of biological organization, such as ecosystems or organismic development? 相似文献
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R LoBrutto G W Smithers G H Reed W H Orme-Johnson S L Tan J S Leigh 《Biochemistry》1986,25(19):5654-5660
Pulsed electron paramagnetic resonance spectroscopy has been used to detect Mn(II)-ligand superhyperfine couplings in complexes with creatine kinase and in the Mn(II) metalloprotein concanavalin A. Electron spin-echo envelopes from Mn(II), bound in these complexes, are modulated by superhyperfine interactions between Mn(II) and nearby, weakly coupled nuclear spins. The characteristic frequencies of the modulations were obtained by Fourier transformation of the three-pulse, spin-echo envelopes. In transition-state analogue complexes of creatine kinase (enzyme-MnIIADP-anion-creatine), superhyperfine interactions from the directly coordinated nitrogen of the thiocyanate ligand give envelope modulations. The source of the modulations was confirmed by measurements with the 14N and 15N forms of thiocyanate. On the other hand, the nitrogen of coordinated nitrate, which is two bonds removed from the paramagnetic center, does not produce detectable modulations. In spectra for Mn(II) concanavalin A, envelope modulations are detected due to the nitrogen of the coordinated histidine residue. Complexes prepared in 2H2O give strong signals due to weakly coupled 2H. For Mn(II)-doped single crystals of sodium pyrophosphate, signals are observed in the frequency domain spectra that are due to coupling from 31P. Phosphorus signals from the ADP ligand in complexes with creatine kinase show approximately the same coupling constant but have a much broader line width. 相似文献
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A procedure for the culture of Solanum etuberosum mesophyll protoplasts with subsequent shoot regeneration is described. Several factors affected protoplast yield, colony formation, and shoot regeneration from in vitro plants. A protoplast isolation medium with 0.6 M sucrose produced twice the yield as one with 0.3 M sucrose. uowever, a higher concentration of osmoticum was inhibitory to colony development unless it was diluted into a lower osmoticum medium in a bilayer system. A 16 hour light/8 hour dark photoperiod for stock plants allowed twice the protoplast yield compared to plants grown under continuous light but no effect was found on subsequent colony formation or shoot regeneration. The concentrations of four major salts in the protoplast plating medium were critical for a high frequency of colony formation from protoplasts. Levels of 0.25 × or 1 × were considerably better than 4 ×. Fast colony formation, but at a lower efficiency, was obtained with a monolayer plating method. A bilayer plating system allowed a higher efficiency but colonies developed more slowly. For the best treatments, the frequency of colony formation from protoplasts ranged from 2.4 to 3.6 × 10-3 with 37% to 66% of the colonies producing shoots ten weeks after protoplast isolation.Cooperative investigation of the USDA-ARS and the Wisconsin Agric. Exp. Stn. 相似文献
10.
Vacuoles isolated from the storage roots of red beet (Beta vulgaris L.) accumulate sucrose via two different mechanisms. One mechanism transports sucrose directly, and its rate is increased by the addition of MgATP. The other mechanism utilizes uridine diphosphate glucose (UDP-glucose) to synthesize and simultaneously transport sucrose phosphate and sucrose into the vacuole. This group translocation mechanism has also been found in sugarcane vacuoles. As in sugarcane, the beet group translocator does not require fructose 6-phosphate, nor is the latter substance transported into the vacuole. The uptake of UDP[14C]glucose in inhibited by high concentrations of osmoticum.Abbreviations EDTA
ethylenediaminetetraacetic acid
- Hepes
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- UDP
uridine 5-diphosphate 相似文献