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951.
Fons A.L.J. Peters Guus A.B. Smit Arie T.M. Van Diepen Klaas Krab Ruud Kraayenhof 《BBA》1984,766(1):179-187
Cytochrome redox changes and electric potential generation are kinetically compared during cyclic electron transfer in Photosystem-I-enriched and Photosystem-II-depleted subchloroplast vesicles (i.e., stroma lamellae membrane vesicles) supplemented with ferredoxin using a suitable electron donating system. In response to a single-turnover flash, the sequence of events is: (1) fast reduction of cytochrome b-563 (t0.5 ≈ 0.5 ms) (2) oxidation of cytochrome c-554 (t0.5 ≈ 2 ms), (3) slower reduction of cytochrome b-563 (t0.5 ≈ 4 ms), (4) generation of the ‘slow’ electric potential component (t0.5 ≈ 15–20 ms), (5) re-reduction of cytochrome c-554 (t0.5 ≈ 30 ms) and (6) reoxidation of cytochrome b-563t0.5 ≈ 90 ms). Per flash two cytochrome b-563 species turn over for one cytochrome c-554. These b-563 cytochromes are reduced with different kinetics via different pathways. The fast reductive pathway proceeds probably via ferredoxin, is insensitive to DNP-INT, DBMIB and HQNO and is independent on the dark redox state of the electron transfer chain. In contrast, the slow reductive pathway is sensitive to DNP-INT and DBMIB, is strongly delayed at suboptimal redox poising (i.e., low ratio) and is possibly coupled to the reduction of cytochrome c-554. Each reductive pathway seems obligatory for the generation of about 50% of the slow electric potential component. Also cytochrome c-559LP (LP, low potential) is involved in Photosystem-I-associated cyclic electron flow, but its flash-induced turnover is only observed at low preestablished electron pressure on the electron-transfer chain. Data suggest that cyclic electron flow around Photosystem I only proceeds if cytochrome b-559LP is in the reduced state before the flash, and a tentative model is presented for electron transfer through the cyclic system. 相似文献
952.
The conditions used in some immunoblot procedures can fail to detect calmodulin, S100 proteins, and other proteins with similar physical properties. We describe here some of the basis of this difficulty, and provide an immunoblot protocol that allows the rapid and reproducible detection of calmodulin and S100 beta in crude biological samples. These proteins are rapidly transferred from sodium dodecyl sulfate-polyacrylamide gels to membrane matrices, and retention on the matrix is enhanced by a glutaraldehyde fixation step. Either nitrocellulose or a positively charged membrane filter (ZetaProbe) can be used as the immobilizing matrix. By combining microslab gel electrophoresis, 30 min electrophoretic transfer, and glutaraldehyde fixation of nitrocellulose paper, an immunoblot analysis can be done in an 8-hr day. 相似文献
953.
The cytologic findings in two histologically confirmed cases of granuloma inguinale are presented. The Papanicolaou staining method used in routine cytology screening proved to be suitable for the detection of the characteristic Donovan bodies in smears of the vulvar lesions. 相似文献
954.
Periodic acid oxidation in methanol followed by incubation with 1, 1-dimethylhydrazine results in release of diacylglycerols from 1,2-diacyl-3-glycosyl-sn-glycerols. During hydrazinolysis of oxidized monogalactosyl diacylglycerol, an intermediate hydrazone derivative was observed which was isolated and identified. The diacylglycerols recovered are 1,2-diacyl isomers containing the same fatty acid mixtures as the intact glycolipids. The yields of diacylglycerols released from plant monogalactosyl-, digalactosyl-, and sulfoquinovosyl diacylglycerols were in the range of 30-50%. The method may be used for analysis of molecular species and for preparative purposes. 相似文献
955.
The depression of the phase-transition temperature of dimyristoyl- and dipalmitoylphosphatidylcholine vesicles induced by phenol has been investigated by fluorescence polarization. This effect is strongly pH and concentration dependent. Only the uncharged phenol molecule influences the fluidity of the bilayer so that the interaction of phenol with the bilayer can be situated in the hydrophobic acyl chain region. Direct measurements of the partitioning of phenol in the phospholipid vesicles confirm these results and show a limited and concentration-dependent solubility. Phase-transition temperature depressions, obtained from thermodynamic analysis of partition coefficient measurement, are in good agreement with the experimental values. 相似文献
956.
H S Van Walraven E Koppenaal H J Marvin M J Hagendoorn R Kraayenhof 《European journal of biochemistry》1984,144(3):563-569
The lipid specificity for the enzymatic and proton-translocating functions of a reconstituted thermophilic ATPase complex has been investigated. The proteoliposomes were prepared from the ATPase complex of the thermophilic cyanobacterium Synechococcus 6716 and various lipids and lipid mixtures extracted from this organism and from a related mesophilic strain. Some commercial lipids were used as well. An improved method of lipid extraction from chlorophyll-containing membranes is presented. This method is based on acetone extraction and additional chlorophyll separation and results in higher yields, less chlorophyll contamination and a simpler procedure than the conventional methods based on chloroform/methanol extraction. The lipids of Synechococcus 6716 thus extracted were fractionated by thin-layer chromatography. The fatty acyl chain composition of the separated lipids was analyzed by gas chromatography. The coupling quality of the reconstituted ATPase proteoliposomes made of different lipids was tested by a membrane-bound fluorescent probe and uncoupler stimulation of ATP hydrolysis. None of the separated lipids alone was able to produce a well-coupled system. The best results were obtained with the native lipid mixture. The minimum requirement was the combination of a typical bilayer-forming lipid and the non-bilayer (hexagonal II structure)-forming monogalactosyldiacylglycerol. Lipids from the mesophilic Synechococcus 6301 and commercial lipids (also mesophilic) produced poorly coupled vesicles but significant improvement was obtained when thermophilic monogalactosyldiacylglycerol was included. Both the reconstituted and solubilized ATPase complex have a sharp temperature optimum at 50 degrees C. The effect of reconstitution and measurement temperatures on the yield of well-coupled vesicles from different lipid sources was also studied. 相似文献
957.
Detection of a yeast polyphosphate fraction localized outside the plasma membrane by the method of phosphorus-31 nuclear magnetic resonance 总被引:3,自引:0,他引:3
J P Tijssen J Van Steveninck 《Biochemical and biophysical research communications》1984,119(2):447-451
Non-penetrating cations, like UO2+(2) and Eu3+, are bound to the outside of yeast cells in a reversible fashion. Binding of these ions was attended with a decrease of the 31P NMR polyphosphate signal. Subsequent addition of EDTA to the suspension restored the original spectrum. These experiments confirm the localization of a polyphosphate fraction outside the plasma membrane of yeast. 相似文献
958.
Bends in human mitotic metaphase chromosomes, including a bend marking the X-inactivation center. 总被引:3,自引:2,他引:1
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Bends in mitotic metaphase chromosomes are not distributed randomly throughout the karyotype. The frequency of bends at centromeres is positively correlated with the relative length of the chromosomes and negatively correlated with the centromere index (more bends in metacentrics, fewer in acrocentrics). The frequency of bends in the noncentromeric regions (except at Xq13-Xq21) is positively correlated with the relative length of chromosome arms. A bend at Xq13.3 to Xq21.1 was more frequent than a bend in any other region of the karyotype, centromeric or noncentromeric. It was observed in one member of the X-chromosome pair in 63% of 46,XX cells. In contrast, it was observed in only 2% of 46,XY cells. RBG-staining showed that this specific bend is confined to the lyonized X chromosome. These observations in cells from normal subjects were confirmed using G-banding and RBG-staining on cells from nine subjects with different X-chromosome abnormalities and on metaphases from amniotic fluid cell and lymphocyte cultures. The "center for Barr body condensation" has been localized to the region between Xq11.2 and Xq21.1. The functional and structural relationship is unclear, but we believe this highly specific bend may represent a visible manifestation of the condensation process; it could represent the first folded (and last unfolded) position, upon or around which the rest of the chromosome condenses. The late replication of this region may also be a factor. The smallest region of overlap (SRO) for the X-chromosome inactivation center and the specific chromosome bend is Xq13.3 to Xq21.1. 相似文献
959.
The structural distortion of oligonucleotides upon cis-PtCl2(NH3)2[d(T-C-T-C-G-G-T-C-T-C)-N7(5), N7(6)] reveals shifting of 4 phosphorus resonances due to platination. 3 Resonances could be assigned by selective 31P-irradiation, showing P(6) (P between the two Gs) to be shifted 1.5 ppm to low field. In the concomitant double strands P(6) is shifted 0.9 ppm to lower field. A similar peak has been observed in platinated salmon sperm DNA (37 degrees C), indicating that Pt-binding to GpG-fragments in DNA is similar to that found for the decanucleotide, so the distortion of DNA might be comparable. 相似文献
960.
The mechanism by which ethanol decreases the concentration of fructose 2,6-bisphosphate in the liver. 总被引:17,自引:3,他引:14
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The intragastric administration of ethanol to fed rats caused in their liver, within about 1 h, a 20-fold decrease in the concentration of fructose 2,6-bisphosphate, an activation of fructose 2,6-bisphosphatase, an inactivation of phosphofructo-2-kinase but no change in the concentration of cyclic AMP. Incubation of isolated hepatocytes in the presence of ethanol caused a rapid increase in the concentration of sn-glycerol 3-phosphate and a slower and continuous decrease in the concentration of fructose 2,6-bisphosphate with no change in that of hexose 6-phosphates. There was also a relatively slow activation of fructose 2,6-bisphosphatase and inactivation of phosphofructo-2-kinase. Glycerol and acetaldehyde had effects similar to those of ethanol on the concentration of phosphoric esters in the isolated liver cells. 4-Methylpyrazole cancelled the effect of ethanol but reinforced those of acetaldehyde. High concentrations of glucose or of dihydroxyacetone caused an increase in the concentration of hexose 6-phosphates and counteracted the effect of ethanol to decrease the concentration of fructose 2,6-bisphosphate. As a rule, hexose 6-phosphates had a positive effect and sn-glycerol 3-phosphate had a negative effect on the concentration of fructose 2,6-bisphosphate in the liver, so that, at a given concentration of hexose 6-phosphates, there was an inverse relationship between the concentration of fructose 2,6-bisphosphate and that of sn-glycerol 3-phosphate. These effects could be explained by the ability of sn-glycerol 3-phosphate to inhibit phosphofructo-2-kinase and to counteract the inhibition of fructose 2,6-bisphosphatase by fructose 6-phosphate. sn-Glycerol 3-phosphate had also the property to accelerate the inactivation of phosphofructo-2-kinase by cyclic AMP-dependent protein kinase whereas fructose 2,6-bisphosphate had the opposite effect. The changes in the activity of phosphofructo-2-kinase and fructose 2,6-bisphosphatase appear therefore to be the result rather than the cause of the decrease in the concentration of fructose 2,6-bisphosphate. 相似文献