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41.
Replacement substitutions of mitochondrial cytochrome and α- and β-chains of haemoglobin have been studied by considering the structural similarity among amino acid residues at the secondary and tertiary structural levels. Secondary structural similarity explains ~70% while tertiary structural similarity explains ~50% of observed replacements for most of the cases. These structural similarities could not account for all the replacement substitutions. The study was extended to consider the composition of codons, and the chemical nature and polarity of the replacing and replaced residues. These also could not individually account for all the affected replacements. In general, no property of amino acid residues is conserved for substitutions occurring at any single position during evolution of proteins. 相似文献
42.
E. Eliopoulos A.J. Geddes M. Brett D.J.C. Pappin J.B.C. Findlay 《International journal of biological macromolecules》1982,4(5):263-268
A putative model for the structure of the relatively independent carboxyl-terminal domain of (rhod)opsin has been developed by use of a combination of several secondary structure prediction methods. The validity of this approach was confirmed by comparing the secondary structure for bacteriorhodopsin as predicted by these methods with its known low resolution structure. The resulting predicted structure agreed well with the experimental data. The model obtained for opsin incorporates two transmembrane α-helical rods linked by an intradiscal loop. Each of the helical sections is interrupted by a short irregular region. One of these includes the lysyl residue to which the chromophore 11-cis retinal is attached. The second non-regular segment, almost opposite the first, contains a cysteinyl and a tryptophanyl residue which may be involved in protein—chromophore interaction. The proposed structure of this whole domain could prove instructive in the elucidation of the primary events of visual transduction. 相似文献
43.
Preservation of proteins in mummified tissues 总被引:1,自引:0,他引:1
R A Barraco 《American journal of physical anthropology》1978,48(4):487-491
Protein material was extracted from the dessicated tissues of several Egyptian mummies and a frozen Eskimo. The distribution and degree of preservation of high molecular weight protein was analyzed by gel filtration, protein assays, amino acid analysis, and polyacrylamide gel electrophoresis. The protein has undergone considerable degradation although some high molecular weight protein (C. 130,000 daltons) remains intact. Amino acid analysis of the extracted protein indicates the basic amino acids have undergone a chemical modification and may represent a point of preferential breakdown in the polypeptide chain. Atomic absorption spectrophotometry of tissue cations suggests a correlation between degree of preservation of mummified tissue and levels of sodium salts (natron) in the tissue. 相似文献
44.
We have previously reported that treatment of CsA with aqueous HCl gives rise to the formation of a number of water-soluble compounds. Two of these were identified from their FAB-MS/MS spectra as open-chain nona- and decapeptides. We describe here the identification of two other main compounds deriving from the same treatment. Identification was rendered possible from the comparison of their FAB-MS/MS spectra with those of methyl and acetyl derivatives. The two compounds are water-soluble, open-chain undecapeptides corresponding to 1,11 seco-CsA and of 4,5 seco-isoCsA, respectively. 相似文献
45.
Microbial production and uptake of nitric oxide in soil 总被引:3,自引:0,他引:3
Abstract Fluxes of NO from three different soils have been studied by a flow-through system in the laboratory as a function of gas flow rate, of NO mixing ratio, and of incubation conditions. The dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by a simple model of simultaneous NO production and NO uptake. By using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios could be determined as function of the soil type and the incubation condition. Gross NO production rates were one to two orders of magnitude larger under anaerobic than under aerobic conditions. NO uptake rate constants, on the other hand, were only 5–8 times larger so that the compensation mixing ratios of NO were in a range of about 1600–2200 ppbv under anaerobic and of about 50–600 ppbv under aerobic conditions. The different soils exhibited similar NO uptake rate constants, but the gross NO production rate and compensation mixing ratio was significantly higher in an acidic (pH 4.7) sandy clay loam than in other less acidic soils. Experiments with autoclaved soil samples showed that both NO production and NO uptake was mainly due to microbial metabolism. 相似文献
46.
Solveig Herrmann Milena Ninkovic Tobias Kohl éva L?rinczi Luis A. Pardo 《The Journal of biological chemistry》2012,287(53):44151-44163
KV10.1 is a voltage-gated potassium channel aberrantly expressed in many cases of cancer, and participates in cancer initiation and tumor progression. Its action as an oncoprotein can be inhibited by a functional monoclonal antibody, indicating a role for channels located at the plasma membrane, accessible to the antibody. Cortactin is an actin-interacting protein implicated in cytoskeletal architecture and often amplified in several types of cancer. In this study, we describe a physical and functional interaction between cortactin and KV10.1. Binding of these two proteins occurs between the C terminus of KV10.1 and the proline-rich domain of cortactin, regions targeted by many post-translational modifications. This interaction is specific for KV10.1 and does not occur with KV10.2. Cortactin controls the abundance of KV10.1 at the plasma membrane and is required for functional expression of KV10.1 channels. 相似文献
47.
48.
Nb1-particles fromNitrobacter agilis were found to be highly stable and could only be disrupted by chemicals or prolonged sonication.Spectra of the Nb1-particles indicated that protein is their major component. They contain no lipid.Highly purified Nb1-particles that were electronmicroscopically free from contaminating membranes, contained 7 different proteins, as shown by sodium dodecyl sulfate-polyacrylamide gelelectrophoresis.Abbreviations SDS
sodium dodecyl sulfate
- PAGE
polyacrylamide-gelelectrophoresis
- M. W.
molecular weight
- O.D.
opitical density
- HAA
hepatitis associated antigen 相似文献
49.
Theresa L. M. Pohl Elisabeth H. Schwab Elisabetta A. Cavalcanti-Adam 《Journal of visualized experiments : JoVE》2013,(78)
Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell differentiation into osteoblasts, thus stimulating healing and de novo bone formation. The clinical use of recombinant human BMP-2 (rhBMP-2) in conjunction with scaffolds has raised recent controversies, based on the mode of presentation and the amount to be delivered. The protocol presented here provides a simple and efficient way to deliver BMP-2 for in vitro studies on cells. We describe how to form a self-assembled monolayer consisting of a heterobifunctional linker, and show the subsequent binding step to obtain covalent immobilization of rhBMP-2. With this approach it is possible to achieve a sustained presentation of BMP-2 while maintaining the biological activity of the protein. In fact, the surface immobilization of BMP-2 allows targeted investigations by preventing unspecific adsorption, while reducing the amount of growth factor and, most notably, hindering uncontrolled release from the surface. Both short- and long-term signaling events triggered by BMP-2 are taking place when cells are exposed to surfaces presenting covalently immobilized rhBMP-2, making this approach suitable for in vitro studies on cell responses to BMP-2 stimulation. 相似文献
50.
Jinrui Gan Kun Qian Jingjing Wan Liang Qiao Weichao Guo Pengyuan Yang Hubert H. Girault Baohong Liu 《Proteomics》2013,13(21):3117-3123
Amino‐functionalized macroporous silica foam (NH2‐MOSF) has been developed as a host reactor to realize highly efficient proteolysis in acidic solutions where normal tryptic reactions cannot occur. The digestion protocol consists simply of adding the functionalized NH2‐MOSF into the protein and trypsin solutions without altering the bulk pH or preloading the enzymes on the materials. With this protocol, digestion of sample fractions from LC can be efficiently realized in the acidic solutions directly. Digestion of a protein fraction extracted from rat liver tissue after LC separation was performed to illustrate this principle, where 103 proteins were successfully identified at pH 3 after 1.5 h of tryptic digestion. 相似文献