共查询到20条相似文献,搜索用时 46 毫秒
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《Journal of Ultrastructure and Molecular Structure Research》1989,102(2):170-177
STM imaging was carried out on the outer surface of bacteriophage T4 type III polyheads, after freeze-drying and coating with a thin conducting film. By taking advantage of the high resolution power of the STM especially in the z-direction (i.e., perpendicular to the support), an apparent surface topography of only about 1 nm height was resolved. The average capsomere morphology was determined by correlation averaging. Because of the high signal-to-noise ratio of the tunneling data, only a few unit cells were needed to reveal a stable average. Both the topology as well as the absolute height of the polyheads have been reproduced in several experiments. The influence of the tip geometry on the STM topographs is discussed. 相似文献
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《Journal of Biomedical Engineering》1991,13(4):328-334
A porous bioglass ceramic was prepared from a finely pulverized bioglass powder mixed with particles of two sizes (5 and 500 μm) of 30% by weight with the foaming agent polyethylene glycol 4000 (HO (C2H4O) nH). The batch composition of the bioglass was Na2O 12%, CaO 28%, SiO2 50% and P2O5 10% by weight. The specimens, formed by pressing, were sintered in a high temperature furnace. In this study we are concerned with the preparation and microstructure of the material and its performance in biological tests. The microstructure and crystalline phases of the material were investigated by differential thermal analysis, X-ray diffraction analysis, transmission electron microscopy and scanning electron microscopy. In a biomedical examination, it was shown that the porous material was compatible with animal tissues. The microstructure of the implant indicated that newly grown bone interlocked well with the glass ceramic and that macropores and micropores were distributed uniformly in the material, which provided channels for bone ingrowth and improved the microscopic bioresorption. 相似文献
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We have studied ouabain-resistant, external sodium-stimulated, lithium efflux (LiNa countertransport) in red blood cells from 21 borderline hypertensives with at least one hypertensive first degree relative (BH-F), 19 borderline hypertensives without family history of essential hypertension (BH-NF), and 35 age-matched normotensive subjects. The data indicate the finding of an increased LiNa countertransport in all BH (F+NF), but with a significant overlap between BH values and control ones: LiNa countertransport is significantly higher only in BH-F but it is normal in BH-NF. Moreover, there is a significant correlation of LiNa countertransport to total peripheral resistance but not to mean blood pressure in all hypertensive patients. It is suggested that in BH the increase of erythrocyte Na flux is mediated by the NaNa exchange diffusion, and its abnormality may be associated to the hereditary trait of essential hypertension rather than the high blood pressure per se, probably resulting in the development of hypertension, through the increased vascular smooth muscle tone. 相似文献
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《Inorganica chimica acta》1987,131(1):33-37
From the Cu(II)NCO−3(5)-methylpyrazole (mpz) system two compounds Cu(NCO)2(mpz)2 and four compounds Cu(mpz·NCO)2 were isolated. The latter compounds contain carbamoylmethylpyrazolate anions as chelate ligands and are coligand isomers of the cyanate compounds. According to the results of indirect structural methods, the Cu(NCO)2(mpz)2 complexes have pseudooctahedral structures and differ in their polyhedron distortions. The Cu(mpz·NCO)2 complexes show tetragonally distorted six or five coordinate structures, possibly differing also by the methyl group position on the pyrazole ring. 相似文献
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Anika?M.?Helferich Wolfgang?P.?Ruf Veselin?Grozdanov Axel?Freischmidt Marisa?S.?Feiler Lisa?Zondler Albert?C.?Ludolph Pamela?J.?McLean Jochen?H.?Weishaupt Karin?M.?Danzer
Background
Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS) are both neurodegenerative diseases leading to impaired execution of movement. α-Synuclein plays a central role in the pathogenesis of PD whereas Cu, Zn superoxide dismutase (SOD1) is a key player in a subset of familial ALS cases. Under pathological conditions both α-synuclein and SOD1 form oligomers and fibrils. In this study we investigated the possible molecular interaction of α-synuclein and SOD1 and its functional and pathological relevance.Results
Using a protein-fragment complementation approach and co-IP, we found that α-synuclein and SOD1 physically interact in living cells, human erythrocytes and mouse brain tissue. Additionally, our data show that disease related mutations in α-synuclein (A30P, A53T) and SOD1 (G85R, G93A) modify the binding of α-synuclein to SOD1. Notably, α-synuclein accelerates SOD1 oligomerization independent of SOD1 activity.Conclusion
This study provides evidence for a novel interaction of α-synuclein and SOD1 that might be relevant for neurodegenerative diseases.10.
《Inorganica chimica acta》1986,121(1):33-37
The known complex [Et4N]3[Fe(MoS4)2] has been shown by EPR and visible spectral studies to react with both thiophenol and selenophenol. The reaction results in a change in the characteristic S=3/2 EPR spectrum of this species from a complex rhombic pattern to one of a very simple axial appearance. Although this effect is similar to that observed for reaction of these species with the iron- molybdenum cofactor of nitrogenase, a moiety known to consist of a FeMoS cluster species, the large excesses of reagents and the long reaction times required for complete formation of product indicate that these reactions are of questionable direct relevance to the biological system. The reaction corresponding to the EPR spectral change from rhombic to axial in the [Fe(MoS4)2]3−/PhSeH system has also been partially characterized by product isolation which indicates that attack by selenol of the two terminal MoS2 moieties in the starting material has occurred. 相似文献
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《Inorganica chimica acta》1987,133(2):295-300
The compound K4[Mo2(SO4)4]Br·4H2O has been made and its crystal structure determined. Space group P4/mnc; unit cell dimensions, a = 11.903(2), c = 8.021(1) Å, V = 1136(1) Å3. The compound is isomorphous with the analogous chloride whose structure has been reported. The MoMo and MoBr distances are 2.169(2) and 2.926(1) Å, respectively and the [Mo2(SO4)4] 3− ions reside on crystallographic special positions with 4/m symmetry. The Raman spectra of both the bromo and chloro compounds have been measured and the MoMo stretching frequency is 370 ± 1.5 cm−1 in each, for the compounds containing the natural isotopic distribution of molybdenum. The chloro compound has been prepared containing the pure isotope 92Mo as well, and the Raman spectra recorded. The v(MoMo) band is shifted by 6.8 ± 0.5 cm−1. The compound K4[Mo2(SO4)4]·2H2O has also been prepared with Mo at natural abundance and with the pure isotope 100Mo, whereby a shift of 8.5 ± 0.5 cm−1 was found. These and other results will be discussed with regard to the similarity of the Raman spectra of the Mo2(S04)43− and M02(S04)44− species. 相似文献
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Lisa Ulbrich Mauro Cozzolino Elettra Sara Marini Ilaria Amori Antonella De Jaco Maria Teresa Carrì Gabriella Augusti-Tocco 《Cellular and molecular neurobiology》2014,34(2):205-213
Cystatin B (CSTB), an inhibitor of the cysteine proteases, belongs to the cathepsin family and it is known to interact with a number of proteins involved in cytoskeletal organization. CSTB has an intrinsic tendency to form aggregates depending on the redox environment. The gene encoding for CSTB is frequently mutated in association with the rare neurodegenerative condition progressive myoclonus epilepsy. Increased levels of CSTB have been observed in the spinal cord of transgenic mice modeling SOD1-linked familial amyotrophic lateral sclerosis, a fatal neurodegenerative disease affecting motoneurons. In the present study, we have investigated the relationship occurring between the expression of SOD1 and CSTB either wild-type or double-cysteine substitution mutant (Cys 3 and Cys 64). Whether or not there is a physical interaction between the two proteins was also investigated in overexpression experiments using a human neuroblastoma cell line and mouse-immortalized motoneurons. Here we report evidences for a reciprocal influence of CSTB and SOD1 at the gene expression level and for a direct interaction of the two proteins. 相似文献
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《生物化学与生物物理学报:生物膜》1986,854(2):298-306
Classical NaCa exchange models are based on a symmetric carrier system where Na and Ca competing from the same site, can produce net movement of the other against its electrochemical gradient. We have explored this symmetric assumption by studying the Cao and Nao-dependent Na efflux in dialyzed squid axons in which proper control of both external and internal medium was achieved. The results show: (1) In axons dialyzed without Cai and ATP, Cao-dependent Na efflux cannot be detected even in the absence of Nao. Under these conditions, the level of Na efflux (1 pmol · cm−2 · s−1) is close to that predicted by an electrical ‘leak’. (2) In axons dialyzed with Cai (100 μM) and without ATP, Na efflux measured in 440 mM Nao, is about 4–5 pmol · cm−2 · s−1 and rather insensitive to Cao between 0 and 10 mM. However, in the absence of Nao, a Cao-dependent Na efflux is observed similar in magnitude to that found in the presence of external Na. (3) In the presence of both Cai and ATP, Na efflux into artificial sea-water (440 mM Na, 10 mM Ca) is 18 pmol · cm−2 · s−1. In the absence of Nao the efflux of Na is 7.5 pmol · cm−2 · s−1. In the absence of both Nao and Cao the efflux is close to ‘leak’. With full Nao but no Cao, the Na efflux average 12.6 pmol · cm−2 · s−1. These results indicate a marked asymmetry in the modus operandi of the NaCa exchange system with respect to Cai and ATP. These two substrates are required from the cis side to promote Cao-dependent Na efflux (reversal NaCa exchange). 相似文献
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《Inorganica chimica acta》1986,121(1):13-17
Two new dinuclear μ-cyano complexes, cis-[(en)(tn)FCrNCPt(CN)3] and cis-[(chxn)(tn)FCrNCPt(CN)3] en=ethylenediamine, tn=1,3-diaminepropane and chxn=1,2-cyclohexanediamine) have been obtained by solid state heating of the trans[Cr(aa)(bb)F(H2O)][Pt(CN)4] salts. These complexes have been characterized by chemical analysis, electronic and IR spectra. The dinuclear complexes show strong PtPt interaction both in the solid state and in solution. The association constant of the oligomers formed has been calculated and correlated with the size of the amine ligands. An orbital explanation is proposed to account for the enhancement of the PtPt interaction in the dinuclear complexes relative to the complex salts. 相似文献
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《Inorganica chimica acta》1986,119(1):43-47
The reaction of hexamethyldisilazane with the μ-oxo iron SALEN dimer in toluene under N2 gives the μ-heterobinuclear title complex, FeC19H23N203Si. Crystals of the compound are monoclinic, space group P21/c with a = 6.087(2), b = 10.497(3), c = 28.567(7) Å, β = 97.78(2) and Z = 4. Solution of the structure by direct methods led to a final weighted and unweighted R factors of 6.2 and 5.6%, respectively. The coordination geometry of the iron center is square-pyramidal with the iron displaced 0.56 Å from the best least-squares plane of the coordinating oxygens and nitrogens of the SALEN ligand. The FeOSi angle is bent at 142.7°. The FeOSi linkage does not hydrolyze under neutral pH conditions. 相似文献