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排序方式: 共有187条查询结果,搜索用时 15 毫秒
1.
The protease-protected 30 kDa domain of SecA is largely inaccessible to the membrane lipid phase 总被引:2,自引:0,他引:2
SecA binds to the inner membrane of Escherichia coli through low affinity lipid interactions or with high affinity at SecYEG, the integral domain of preprotein translocase. Upon addition of preprotein and nucleotide, a 30 kDa domain of SecYEG-bound SecA is protected from proteolysis via membrane insertion. Such protection could result from some combination of insertion into the lipid phase, into a proteinaceous environment or across the membrane. To assess the exposure of SecYEG-bound SecA to membrane lipids, a radiolabeled, photoactivatable and lipid-partitioning crosslinker, 3-trifluoromethyl-3-(m[125I]iodophenyl) diazirine benzoic acid ester, was incorporated into inner membrane vesicles. The 30 kDa domain of SecYEG-bound SecA, inserted into the membrane in response to translocation ligands, is 18-fold less labeled than SecY, which is labeled effectively. In contrast, incorporation of the purified 30 kDa SecA fragment into crosslinker-containing detergent micelles or addition of detergent to crosslinker-containing membranes bearing the protease-protected SecA domain readily allows for labeling of this domain. We propose that the protease-inaccessible 30 kDa SecA domain is shielded from the fatty acyl membrane phase by membrane-spanning SecYEG helices and/or is largely exposed to the periplasm. 相似文献
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S Vasil'ev KD Irrgang T Schr?tter A Bergmann HJ Eichler G Renger 《Canadian Metallurgical Quarterly》1997,36(24):7503-7512
The protein composition, steady state and time-resolved fluorescence emission spectra were studied in solubilized and aggregated LHCII complexes, that were prepared according to two different isolation protocols: (1) by fractionation of cation-depleted thylakoid membranes using the non-ionic detergent Triton X-100 according to the procedure of Burke et al. [(1978) Arch. Biochem. Biophys. 187, 252-263] or (2) by solubilization with N-beta-dodecyl maltoside (beta-DM) of photosystem II (PSII) membrane fragments in the presence of cations [Irrgang et al. (1988) Eur. J. Biochem. 178, 207-217]. Based on the analysis of the decay-associated emission spectra measured at 10 and 80 K five long-wavelength chlorophyll species were identified in aggregated LHCII complexes. These five forms are characterized by emission maxima at 681.5, 683, 687, 695, or 702 nm. All of these forms were found in both types of LHCII preparations but the relative amounts and temperature dependency of these species were markedly different in the aggregated LHCII complexes isolated by the two procedures. It was found that these differences cannot be simply explained by effects due to using a less mild detergent as beta-DM or by an ionic influence of Ca2+. Biochemical analysis of the protein composition showed that beta-DM type LHCII consists of all the chlorophyll (Chl)binding proteins belonging to the antenna system of PSII except the CP29 type II gene product (CP29). In contrast, the Triton X-100-solubilized LHCII is highly depleted in CP26 (CP 29 type I gene product) and is contaminated by a variety of unidentified polypeptides. It is proposed that the aggregates of LHCII prepared using Triton X-100 acquire specific spectral and kinetic features due to interaction between the bulk of LHCII subunits and minor protein(s). 相似文献
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Jens Eichler Jürgen Rödel Ulrich Eisele Mark Hoffman 《Journal of the American Ceramic Society》2007,90(9):2830-2836
This paper considers fracture strength, fracture origins, and hydrothermal degradation of 3Y-TZP with grain sizes in the range of 110–480 nm. Biaxial fracture strength testing was used to show that the fracture strength increases with grain size and is governed by the concurrent change in fracture toughness. Hydrothermal degradation was studied by means of fractography, Raman microscopy and its effect on fracture strength. Up to 200 nm grain size, hydrothermal degradation of strength is limited. Larger grain sizes exhibit either premature failure or an increase in strength. A surface transformation zone was found to be responsible for both phenomena. 相似文献
6.
Poly(p-tert-butoxycarbonyloxystyrene): a convenient precursor to p-hydroxystyrene resins 总被引:1,自引:0,他引:1
An efficient synthetic route to pure, high molecular weight poly(p-hydroxystyrene) is reported. The route involves synthesis of a new monomer, p-tert-butoxycarbonyloxystyrene, polymerization by radical initiation or by cationic initiation in liquid SO2, followed by thermolysis or acidolysis of the tert-butoxycarbonyl protecting group. Porous, crosslinked resin beads containing the nucleophilic, phenol pendant group have been prepared in a similar fashion from the precursor terpolymer of p-tert-butoxycarbonyloxystyrene, styrene and divinylbenzene. The utility of this resin for solid-phase synthesis has been demonstrated. 相似文献
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Lucas Weißenborn Elie Richel Helena Hüseman Julia Welzer Silvan Beck Simon Schfer Heinrich Sticht Klaus Überla Jutta Eichler 《International journal of molecular sciences》2022,23(11)
Based on the structure of a de novo designed miniprotein (LCB1) in complex with the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, we have generated and characterized truncated peptide variants of LCB1, which present only two of the three LCB1 helices, and which fully retained the virus neutralizing potency against different SARS-CoV-2 variants of concern (VOC). This antiviral activity was even 10-fold stronger for a cyclic variant of the two-helix peptides, as compared to the full-length peptide. Furthermore, the proteolytic stability of the cyclic peptide was substantially improved, rendering it a better potential candidate for SARS-CoV-2 therapy. In a more mechanistic approach, the peptides also served as tools to dissect the role of individual mutations in the RBD for the susceptibility of the resulting virus variants to neutralization by the peptides. As the peptides reported here were generated through chemical synthesis, rather than recombinant protein expression, they are amenable to further chemical modification, including the incorporation of a wide range of non-proteinogenic amino acids, with the aim to further stabilize the peptides against proteolytic degradation, as well as to improve the strength, as well the breadth, of their virus neutralizing capacity. 相似文献
9.
Boersch H. Eichler H. Pfundstein M. Wiesemann W. 《Quantum Electronics, IEEE Journal of》1974,10(6):501-504
The frequency of one axial mode of a three-mode He/Ne laser can be tuned independently from the other modes if a third mirror is added to the usual two laser mirrors. Provided the adjustment is correct, the frequency shift is proportional to a change of the optical path length between the third mirror and the neighboring laser mirror. By observing the beat frequency of the laser, measurements of optical path variations down to 10-5Å are possible. 相似文献
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