全文获取类型
收费全文 | 62篇 |
免费 | 2篇 |
专业分类
64篇 |
出版年
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 1篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1995年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有64条查询结果,搜索用时 0 毫秒
1.
Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections 总被引:15,自引:4,他引:11
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusabler ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A.V. Somlyo, and A.P. Somlyo. 1976. Ultramicros. 1:317-339.) of freeze-dried ultrathin cryto sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of CI in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition if striated muscle. There was no evidence of sequestered CI in the terminal cisternae of resting muscles, although calcium (66mmol/kg dry wt +/- 4.6 SE) was detected. The values of [C1](i) determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial Ci ratio of 2.4 +/- 0.88 SD. The elemental concentrations (mmol/kg dry wt +/- SD) of muscle fibers measured with 0.5-9-μm diameter electron probes in normal frog striated muscle were: P, 302 +/- 4.3; S, 189 +/- 2.9;C1, 24 +/- 1.1;K, 404 +/- 4.3, and Mg, 39 +/- 2.1. It is concluded that: (a) in normal muscle the "excess CI" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic C1 in low [K](0) solutions exceeds that predicted by a passive electrochemical distribution. Hypertonic 2.2 X NaCl, 2.5 X sucrose, or 2.2 X Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P = approximately (6 Ca + 1 Mg)/6P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules. 相似文献
2.
3.
AV Shevchenko IG Budzanivska TP Shevchenko VP Polischuk D Spaar 《Archives Of Phytopathology And Plant Protection》2013,46(2):139-146
The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants. 相似文献
4.
5.
6.
Priamchuk SD Fursova NK Abaev IV Kovalev IuN Shishkova NA Pecherskikh EI Korobova OV Astashkin EI Pachkunov DM Kruglov AN Ivanov DV Sidorenko SV Svetoch EA Diatlov IA 《Antibiotiki i khimioterapii͡a》2010,55(9-10):3-10
Nosocomial bacterial isolates collected within 2003-2004 (n=411) and 2005-2007 (n=422) were highly resistant to cephalosporins III-IV and antibacterials of other groups (aminoglycosides, fluoroquinolons, chloramphenicol, and co-trimoxazole). Genes encoding TEM, SHV, CTX-M, OXA-2, and AmpC types of beta-lactamases (BLs) in the E. coli, Klebsiella spp., and Enterobacter spp. isolates were detected using polymerase chain reaction (PCR). Prevalent CTX-M-type BLs were detected in 85% of the E. coli, 87% of the Klebsiella spp., and 38% of the Enterobacter spp. isolates of the first strain collection and in 94% of the E. coli, 91% of the Klebsiella spp., and 38% of the Enterobacter spp. isolates of the second one. Genes belonging to three subtypes of blacTx-M genes were identified: bla(CTX-M-1) (228 bla(CTX-M-15) and six bla(CTX-M-3) of the first strain collection; 275 bla(CTX-M-15), three bla(CTX-M-3), and one bla(CTX-M-22) of the second one), bla(CTX-M-2) (one bla(CTX-M-5) of the first strain collection and one bla(CTX-M-2) of the second one), bla(CTX-M-9) (17 bla(CTX-M-14) and one bla(CTX-M-9) of the first strain collection; seven bla(CTX-M-14) and one bla(CTX-M-9) of the second one). Three isolates of the first strain collection and one isolate of the second one carried two genes belonging to two different subtypes, i.e., bla(CTX-M-15) and bla(CTX-M-14) simultaneously. The bacterial isolates had high levels of associative resistance to ciprofloxacin, co-trimoxazole, gentamicin, amikacin, and chloramphenicol associated with the resistance gene cassettes aadA1, aadA2, aadA5, aadB, aacA4, aac(6')Ib; dfrA1, dfrA5, dfrA12, dfrA17, cmlA1, ereA2, and catB8 in the class 1 integrons and the resistance gene cassettes dfrA1, sat1, and aadA1 in the class 2 integrons. 相似文献
7.
Trevor D. Rapson Andrei V. Astashkin Kayunta Johnson-Winters Paul V. Bernhardt Ulrike Kappler Arnold M. Raitsimring John H. Enemark 《Journal of biological inorganic chemistry》2010,15(4):505-514
Continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopy have been used to characterize two variants
of bacterial sulfite dehydrogenase (SDH) from Starkeya novella in which the conserved active-site arginine residue (R55) is replaced by a neutral amino acid residue. Substitution by the
hydrophobic methionine residue (SDHR55M) has essentially no effect on the pH dependence of the EPR properties of the Mo(V) center, even though the X-ray structure
of this variant shows that the methionine residue is rotated away from the Mo center and a sulfate anion is present in the
active-site pocket (Bailey et al. in J Biol Chem 284:2053–2063, 2009). For SDHR55M only the high-pH form is observed, and samples prepared in H2
17O-enriched buffer show essentially the same 17O hyperfine interaction and nuclear quadrupole interaction parameters as SDHWT enzyme. However, the pH dependence of the EPR spectra of SDHR55Q, in which the positively charged arginine is replaced by the neutral hydrophilic glutamine, differs significantly from that
of SDHWT. For SDHR55Q the blocked form with bound sulfate is generated at low pH, as verified by 33S couplings observed upon reduction with 33S-labeled sulfite. This observation of bound sulfate for SDHR55Q supports our previous hypothesis that sulfite-oxidizing enzymes can exhibit multiple pathways for electron transfer and product
release (Emesh et al. in Biochemistry 48:2156–2163, 2009). At pH ≥ 8 the high-pH form dominates for SDHR55Q. 相似文献
8.
Andrei V. Astashkin Arnold M. Raitsimring F. Ann. Walker Christopher Rensing Megan M. McEvoy 《Journal of biological inorganic chemistry》2005,10(3):221-230
Electron paramagnetic resonance (EPR) spectroscopy has been used to structurally characterize the copper-binding site in CusF protein from Escherichia coli. The EPR spectra indicate a single type II copper center with parameters typical for nitrogen and oxygen ligands (A~200 G, g~2.186, g~2.051). The pulsed EPR data show that one of the ligands to Cu2+ is an imidazole ring of a histidine residue. The remote amino nitrogen of this imidazole ring is readily observed by electron spin-echo envelope modulation spectroscopy, while the imino nitrogen that is directly coordinated to the Cu2+ ion is observed by pulsed electron–nuclear double resonance (ENDOR). In addition, the ENDOR spectra reveal the presence of one more nitrogen ligand that was assigned to be a deprotonated peptide nitrogen. Apart from the two nitrogen ligands, it has been established that there are two nearby hydroxyl protons, although whether these belong to a single equatorial water ligand or two equatorial hydroxide ligands is not known.
相似文献
Megan M. McEvoyEmail: Phone: +1-520-6213489Fax: +1-520-6211697 |
9.
Alexander M. Khenkin Debbie Baute Andrei V. Astashkin Daniella Goldfarb Ronny Neumann 《Inorganica chimica acta》2006,359(9):3072-3078
An EPR spectrum of as synthesized [G.A. Tsigdinos, C.J. Hallada, Inorg. Chem. 7 (1968) 437-441], orange colored, H5PV2Mo10O40 polyoxometalate showed the presence of a reduced vanadium(IV) addenda atom. Surprisingly, further 31P ENDOR (electron-nuclear double resonance) measurements indicated the absence of a phosphorous heteroatom leading to the suggestion that H5VVVIVMo11O40 exists as a previously unrecognized impurity in the typically synthesized H5PV2Mo10O40 compound. H5/4PVVO4VIV/VMo11O36 was then synthesized in low yield (0.8 mol%) by omitting the addition of phosphate in a typical H5PV2Mo10O40 preparation. The molecular formulation and structure was supported by X-ray crystallography, infrared and mass spectrometry. Further use of EPR/ENDOR/ESEEM (electron-spin echo envelope modulation) allowed the formulation of [VVVIVMo11O40]5− as [VVO4VIVMo11O36]5−. Accordingly, the polyoxometalate has a heteroatom core with 11 molybdenum addenda and one VO2+ moiety at the polyoxometalate surface. The redox potential and the catalytic activity of the new vanadomolybdate polyoxometalate compound were essentially identical to the often-studied H5PV2Mo10O40 polyoxometalate isomeric mixture. 相似文献
10.