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1.
Ba(2+) current through the L-type Ca(2+) channel inactivates essentially by voltage-dependent mechanisms with fast and slow kinetics. Here we found that slow inactivation is mediated by an annular determinant composed of hydrophobic amino acids located near the cytoplasmic ends of transmembrane segments S6 of each repeat of the alpha(1C) subunit. We have determined the molecular requirements that completely obstruct slow inactivation. Critical interventions include simultaneous substitution of A752T in IIS6, V1165T in IIIS6, and I1475T in IVS6, each preventing in additive manner a considerable fraction of Ba(2+) current from inactivation. In addition, it requires the S405I mutation in segment IS6. The fractional inhibition of slow inactivation in tested mutants caused an acceleration of fast inactivation, suggesting that fast and slow inactivation mechanisms are linked. The channel lacking slow inactivation showed approximately 45% of the sustained Ba(2+) or Ca(2+) current with no indication of decay. The remaining fraction of the current was inactivated with a single-exponential decay (pi(f) approximately 10 ms), completely recovered from inactivation within 100 ms and did not exhibit Ca(2+)-dependent inactivation properties. No voltage-dependent characteristics were significantly changed, consistent with the C-type inactivation model suggesting constriction of the pore as the main mechanism possibly targeted by Ca(2+) sensors of inactivation. 相似文献
2.
The chloroform-methanol extractable lipids of the Gram-negative fresh-water bacteria Arcocella aquatica NO-502 and Flectobacillus major FM were found to contain an unusual ninhydrin-positive glycolipid. It was purified by two-stage silica gel-column chromatography. By the use of IR and (1)H-NMR spectroscopy, mass spectrometry and chemical-degradation experiment, the lipid was established to be 1-O-monoglycosyl ceramide, the carbohydrate moiety of which was the alpha-pyranose-ring form of 7-desoxy-7-amino-D-manno-heptulosonic acid, or 1-hydroxycarbonyl-6-deoxy-6-amino-alpha-D-mannopyranose. The ceramide portion consisted mainly (by 95% in the A. aquatica glycolipid and 80% in the F. major glycolipid) of 2-N-(2'-D-hydroxy-13'-methyltetradecanoyl)-15-methyl-4(E)-hexad ecasph ingenine. The minor molecular species differed from the major one only in fatty acid structure. The glycolipid accounted for 8 and 11% of the total lipids extracted from A. aquatica NO-502 and F. major FM cells, respectively. 相似文献
3.
The discrimination of the angular velocity of ventrodorsal and dorsoventral movement of an acoustic image was studied in nine test subjects. The experiments were performed using an apparent movement produced by consecutive activation of loudspeakers located along an arc in the vertical plane. The differential thresholds were measured by the minimum increment method. As the velocity of an acoustic image movement in opposite directions increased, the values of its mean absolute differential thresholds increased monotonically. Regression lines plotted by linear approximation of these values did not differ significantly. 相似文献
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6.
E S Bulygina V F Gal'chenko N I Govorukhina A I Netrusov D I Nikitin 《Molekuliarnaia genetika, mikrobiologiia i virusologiia》1989,(4):18-24
5S ribosomal RNA sequences of 33 strains of methylotrophic bacteria were determined. Tentative phylogenetic tree was constructed using the maximum topological similarity principle. Strains under study can be divided into 7 separate branches consistently with the current classification of methylotrophic bacteria. More extensive tree was also built to show the position of methylotrophic bacteria with respect to non-methylotrophic ones. One can conclude that the in contrast to obligate methane-oxidizing bacteria, facultative methylotrophic bacteria do not comprise phylogenetically separate domain on the tree. 相似文献
7.
Plasmid content in Yersinia pestis strains of different origin 总被引:5,自引:0,他引:5
Andrew A. Filippov Nikolai S. Solodovnikov Liubov M. Kookleva Olga A. Protsenko 《FEMS microbiology letters》1990,67(1-2):45-48
Plasmid content in 242 Yersinia pestis strains from various natural plague foci of the U.S.S.R. and other countries was studied. Of these strains, 172 (71%) were shown to carry three plasmids described previously of about 6, 45-50 and 60 MDa, respectively. Twenty strains (8%) from different foci harboured additional cryptic plasmids, most often of about 20 mDa in size. Plasmid pPst displayed considerable constancy of its molecular mass. On the contrary, size variations of pCad (45-49 MDa) and, especially, pFra (60-190 MDa) were found. Molecular mass of these plasmids correlated with the host strain origin. 相似文献
8.
A V Nikitin L P Ivanitskaia V M Fishman L E Bodunkova 《Antibiotiki i khimioterapii͡a》1988,33(10):763-767
Multifactor analysis was applied to combined effect of a low molecular immunomodulator of microbial origin and rifampicin on the primary immune response (increased delayed type hypersensitivity and antibody titer) to the antigens of vaccine EV fraction I. Computer processing of the experimental data provided construction of the 2nd order polynomial models satisfactorily describing cellular and humoral responses in the combined therapy. For increasing the informative capacity of the analysis of the polynomial statistic models it was proposed to develop quasimonofactor relationships reflecting the factor effect on the output with changing of the other factors within the studied ranges. Nomograms (equal level lines at fixed values of one factor) were constructed which provided rapid and correct estimation of optimal values for the regulating parameters (drug doses and administration time). Immunostimulating activity of the microbial immunomodulator was estimated quantitatively and conditions for selective regulation of the cellular and humoral responses were determined. 相似文献
9.
Combined action of doxycycline and mytilan, a natural polysaccharide, on the primary immune response to the antigen of the tularemia vaccinal strain in CBA mice was studied. The polysaccharide was used to compensate the immunosuppressive effect of doxycycline high doses on the humoral immune response. The maximum stimulation of the antibody titers as compared to the controls (more than 250 per cent) was observed when mytilan was administered simultaneously with or prophylactically 3 days prior to the antibiotic in doses of 2.5 and 25 mg/kg. The use of mytilan in combination with doxycycline high doses made it possible to compensate the antibiotic-induced decrease of DTH and even to stimulate it as compared to the controls. The highest levels of DTH (150 per cent against the control) were observed when mytilan was administered prophylactically in doses of 2.5 and 11.25 mg/kg 3 days prior to immunization. Mytilan had the highest stimulating effect on antibody production. The combined use of doxycycline and mytilan was characterized by significant stimulation of antibody production and DTH when the dose/time regimens were rational. 相似文献
10.
Roman G. Efremov Dmitry I. Gulyaev Gerard Vergoten Nikolai N. Modyanov 《Journal of Protein Chemistry》1992,11(6):665-675
A new computer-aided molecular modeling approach based on the concept of three-dimensional (3D) molecular hydrophobicity potential has been developed to calculate the spatial organization of intramembrane domains in proteins. The method has been tested by calculating the arrangement of membrane-spanning segments in the photoreaction center ofRhodopseudomonas viridis and comparing the results obtained with those derived from the X-ray data. We have applied this computational procedure to the analysis of interhelical packing in membrane moiety of Na+, K+-ATPase. The work consists of three parts. In Part I, 3D distributions of electrostatic and molecular hydrophobicity potentials on the surfaces of transmembrane helical peptides were computed and visualized. The hydrophobic and electrostatic properties of helices are discussed from the point of view of their possible arrangement within the protein molecule. Interlocation of helical segments connected with short extramembrane loops found by means of optimization of their hydrophobic/hydrophilic contacts is considered in Part II. The most probable 3D model of packing of helical peptides in the membrane domain of Na+, K+-ATPase is discussed in the final part of the work. 相似文献