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1.
Profile of the alpha-bungarotoxin-binding regions on the extracellular part of the alpha-chain of Torpedo californica acetylcholine receptor. 总被引:3,自引:0,他引:3 下载免费PDF全文
The continuous alpha-neurotoxin-binding regions on the extracellular part (residues 1-210) of the alpha-chain of Torpedo californica acetylcholine receptor were localized by reaction of 125I-labelled alpha-bungarotoxin with synthetic overlapping peptides spanning this entire part of the chain. The specificity of the binding was confirmed by inhibition with unlabelled toxin and, for appropriate peptides, with unlabelled anti-(acetylcholine receptor) antibodies. Five toxin-binding regions were localized within residues 1-10, 32-41, 100-115, 122-150 and 182-198. The third, fourth and fifth (and to a lesser extent the first and second) toxin-binding regions overlapped with regions recognized by anti-(acetylcholine receptor) antibodies. The five toxin-binding regions may be distinct sites or, alternatively, different 'faces' in one (or more) sites. 相似文献
2.
C. Steven McDaniel Taghi Manshouri M. Zouhair Atassi 《Journal of Protein Chemistry》1987,6(5):455-461
A peptide corresponding to residues 26–41 of α-bungarotoxin, and closed by a disulfide bond between two cysteine residues
at the amino and C terminal ends of the peptide, was synthesized and the monomeric form was purified. The peptide, which represents
the exposed part of the long central loop of the toxin molecule, was examined for binding to acetylcholine receptor. The peptide
was shown by radiometric titrations to bind radiolabeled receptor, and radiolabeled peptide was bound by receptor. The specificity
of the binding was confirmed by inhibition with the parent toxin. A synthetic analog of the peptide in which Trp-28 was replaced
by glycine had very little (10%) of the original activity. Succinylation of the amino groups of the peptide resulted in virtually
complete (98%) loss of the binding activity. These results indicate that a shortened loop peptide corresponding to the region
26–41 of α-bungarotoxin exhibits binding activities mimicking those of the parent molecule. In this region, Trp-28, and one
or both of Lys-26 and Lys-38, are essential contact residues in the binding to receptor. 相似文献
3.
Biserka Mulac-Jericevic Taghi Manshouri Tsuyoshi Yokoi M. Zouhair Atassi 《Journal of Protein Chemistry》1988,7(2):173-177
A set of 18 synthetic uniform overlapping peptides spanning the entire extracellular part (residues 1–210) of the -subunit of human acetylcholine receptor were studied for their binding activity of125I-labeled -bungarotoxin and cobratoxin. A major toxin-binding region was found to reside within peptide 122–138. In addition, low-binding activities were obtained with peptides 34–49 and 194–210. It is concluded that the region within residues 122–138 constitutes a universal major toxin-binding region for acetylcholine receptor of various species. 相似文献
4.
Biserka Mulac-Jericevic Taghi Manshouri Tsuyoshi Yokoi M. Zouhair Atassi 《The protein journal》1988,7(2):173-177
A set of 18 synthetic uniform overlapping peptides spanning the entire extracellular part (residues 1–210) of the α-subunit of human acetylcholine receptor were studied for their binding activity of125I-labeled α-bungarotoxin and cobratoxin. A major toxin-binding region was found to reside within peptide α122–138. In addition, low-binding activities were obtained with peptides α34–49 and α194–210. It is concluded that the region within residues α122–138 constitutes a universal major toxin-binding region for acetylcholine receptor of various species. 相似文献
5.
Immunochemical cross-reactivity of protein variants has been very frequently used to map protein antigenic sites. The approach is based on the assumption that amino acid substitutions affecting the binding of a protein to its antibody, particularly when monoclonal antibodies (mAbs) are used, must be part of the antigenic site and not far from it. The assumption was investigated in this study by determining the effects of amino acid substitutions outside the antigenic site on the reactivity of six myglobin (Mb) variants with three mAbs of predetermined specificity prepared by immunization with a free synthetic peptide representing region 113–120 (antigenic site 4) of Mb. Two of the Mb variants used had no substitutions within residues 113–120 (the region to which the specificity of the mAbs is directed) and yet exhibited markedly decreased cross-reactions and binding affinities, relative to the reference antigen, sperm-whale Mb. The other three Mb variants possessed substitutions within, as well as outside, region 113–120 and showed very little cross-reactivities. The results of this study, particularly with the Mbs that have no substitutions within the indicated antigenic site, clearly show that substitutions outside the site, and which by design are not part of the site, can influence very markedly the reactivity of the protein variant with the anti-site mAbs. The approach can, therefore, lead to serious errors if used to identify residues of protein antigenic sites. 相似文献
6.
Site recognition by protein-primed T cells shows a non-specific peptide size requirement beyond the essential residues of the site. Demonstration by defining an immunodominant T site in myoglobin. 总被引:2,自引:1,他引:1 下载免费PDF全文
In previous studies, six T sites within myoglobin (Mb) were localized. To define precisely the boundaries of the T sites, a new approach is introduced and applied here to the T site residing within residues 107-120 of Mb. Two sets of peptides were synthesized. One set represents a stepwise elongation by one-residue increments of the Mb sequence. The other set represents an identical stepwise addition of one-residue increments of the Mb sequence, but which were extended by additional unrelated (nonsense) residues to a uniform size of 14 residues. The longer peptides (nonsense-extended) usually gave higher proliferative responses than did their shorter counterparts having the same Mb region. Thus a minimum peptide size is required for optimal T-cell stimulation. The T site subtends, in three high-responder mouse strains, residues 109-119 or 110-120, depending on strain, and, in three low-responder strains, maps to residues 108-120. Thus, in this case, the T site coincides with the site of B-cell recognition and resides in a small discrete surface region of the protein chain. 相似文献
7.
8.
Specific reduction of carboxyl groups in peptides and proteins by diborane 总被引:1,自引:1,他引:0 下载免费PDF全文
1. The reaction of several peptides and proteins with diborane was studied under different conditions to determine those most suitable for the specific reduction of carboxyl groups. 2. In the reaction of model peptides and the cyclic peptides bacitracin and tyrocidin, reduction at 0 degrees was entirely specific for the carboxyl groups without affecting the peptide bonds. Acid amide residues were not reduced. Some tripeptides showed anomalous results in that the C-terminal residue was quite resistant to reduction. 3. Specific reduction of carboxyl groups was achieved in each of the following proteins: human serum albumin, egg albumin, adult human haemoglobin, sperm-whale apomyoglobin, horse heart cytochrome c and egg-white lysozyme. The C-terminal amino acid was usually reduced. 4. Conditions for specific reduction of all available carboxyl groups are not easily found and may vary from one substance to another. Specific reduction of a limited number of available carboxyl groups may be generally accomplished by reactions at -10 degrees . 5. It is suggested that this chemical modification, which has the advantage of permanence, may be useful in studying the role of carboxyl groups in the conformation of proteins and in the biological properties of peptides and proteins. 相似文献
9.
1. The reactions of beta-propiolactone with amino acids were investigated under various conditions of pH and temperature to find those under which the reagent acted with specificity. 2. At pH9.0 and 22 degrees , after 15min. of reaction, at least 85% of each amino acid had reacted, methionine and cystine being the most reactive. 3. At pH7.0 and 22 degrees most amino acids reacted; methionine, cystine and histidine reacted almost entirely, and proline and lysine to a significantly smaller extent. 4. At pH3.0 and 22 degrees further specificity was obtained; methionine and cystine were the only reactive amino acids. 5. Reaction at pH3.0 and 0 degrees was specific for methionine; it was the only amino acid modified even after 145hr. of reaction. 相似文献
10.
M. Z. Atassi 《The Biochemical journal》1964,93(1):189-197