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排序方式: 共有145条查询结果,搜索用时 16 毫秒
1.
Starch supported production of maximum α-amylases (dextrinizing and saccharifying) byFusarium oxysporum andF. scirpi. Addition of gibberellic acid resulted in an increased production of α-amylase. Presence of glucose depressed the enzyme production. pH 4.5 and 4.0 was found to be optimum for the dextrinizing enzyme secreted by both species. The temperature of 25 and 40 °C was optimum for the dextrinizing enzyme secreted byF. oxysporum andF. scirpi, respectively. Saccharifying enzymes of both species showed their optimum at pH 6.9. The optimum temperature for the activity of the saccharifying enzyme was 30 and 40 °C, respectively. 相似文献
2.
We present the three-dimensional (3D) solution structure of a calcium-binding protein from Entamoeba histolytica (EhCaBP), an etiologic agent of amoebiasis affecting millions worldwide. EhCaBP is a 14.7 kDa (134 residues) monomeric protein thought to play a role in the pathogenesis of amoebiasis. The 3D structure of Ca(2+)-bound EhCaBP has been derived using multidimensional nuclear magnetic resonance (NMR) spectroscopic techniques. The study reveals the presence of two globular domains connected by a flexible linker region spanning 8 amino acid residues. Each domain consists of a pair of helix-loop-helix motifs similar to the canonical EF-hand motif of calcium-binding proteins. EhCaBP binds to four Ca(2+) with high affinity (two in each domain), and it is structurally related to calmodulin (CaM) and troponin C (TnC) despite its low sequence homology ( approximately 29%) with these proteins. NMR-derived structures of EhCaBP converge within each domain with low RMSDs and angular order-parameters for backbone torsion angles close to 1.0. However, the presence of a highly flexible central linker region results in an ill-defined orientation of the two domains relative to one other. These findings are supported by backbone (15)N relaxation rate measurements and deuterium exchange studies, which reveal low structural order parameters for residues in the central linker region. Earlier, biochemical studies showed that EhCaBP is involved in a novel signal transduction mechanism, distinct from CaM. A possible reason for such a functional diversity is revealed by a detailed comparison of the 3D structure of EhCaBP with that of CaM and TnC. The studies indicate a more open C-terminal domain for EhCaBP with larger water exposed total hydrophobic surface area as compared to CaM and TnC. Further dissimilarities between the structures include the presence of two Gly residues (G63 and G67) in the central linker region of EhCaBP, which seem to impart it a greater flexibility compared to CaM and TnC and also play crucial role in its biological function. Thus, unlike in CaM and TnC, wherein the length and/or composition of the central linker have been found to be crucial for their function, in EhCaBP, both flexibility as well as amino acid composition is required for the function of the protein. 相似文献
3.
NMR characterisation of a triple stranded complex formed by homo-purine and homo-pyrimidine DNA strands at 1:1 molar ratio and acidic pH. 总被引:1,自引:1,他引:0 下载免费PDF全文
Homo-purine (d-TGAGGAAAGAAGGT) and homo-pyrimidine (d-CTCCTTTCTTCC) oligomers have been designed such that they are complementary in parallel orientation. When mixed in a 1:1 molar ratio, the system adopts an antiparallel duplex at neutral pH with three mismatched base pairs. On lowering the pH below 5.5, a new complex is formed. The NMR results show the coexistence of a intermolecular pyrimidine.purine:pyrimidine DNA triplex and a single stranded oligopurine at this pH. The triplex is stabilized by five T.A:T, four C+.G:C and two mismatched triads, namely, C+.G-T and T.A-C. This triplex is further stabilized by a Hoogsteen C+.G base-pair on one end. Temperature dependence of the imino proton resonances reveals that the triplex dissociates directly into single strands around 55 degrees C, without duplex intermediates. Parallel duplexes are not formed under any of the conditions employed in this study. 相似文献
4.
P Sodano K V Chary O Bj?rnberg A Holmgren B Kren J A Fuchs K Wüthrich 《European journal of biochemistry》1991,200(2):369-377
Escherichia coli glutaredoxin (85 amino acid residues, Mr = 9100), the glutathione-dependent hydrogen donor for ribonucleotide reductase, was purified from an inducible lambda PL, expression system both with a natural isotope content and with uniform 15N labelling. This material was used for obtaining sequence-specific 1H magnetic resonance assignments and the identification of regular secondary structures in the oxidized form of the protein, which contains the redox-active disulfide Cys11-Pro-Tyr-Cys14. Oxidized glutaredoxin contains a four-stranded beta-sheet, with the peripheral strand 32-37 arranged parallel to the strand 2-7, which further combines with the two additional strands 61-64 and 67-69 in an antiparallel fashion. The protein further contains three helices extending approximately from residues 13-28, 45-54 and 72-84. 相似文献
5.
Homonuclear two-dimensional (J, delta) proton spectroscopy has been suggested as a method for the measurement of 1H-31P coupling constants in oligonucleotides. The technique has been applied to a dinucleoside monophosphate G2'p5'C and a deoxydecanucleotide d(ACATCGATGT). PCILO energy calculations have been carried out to find minimum energy conformations with respect to the DNA backbone torsion angle epsilon, and these have been considered for the interpretation of the observed H3'-31P coupling constants in oligonucleotides. 相似文献
6.
7.
High-throughput fluorescent tagging of full-length Arabidopsis gene products in planta 总被引:12,自引:0,他引:12
Tian GW Mohanty A Chary SN Li S Paap B Drakakaki G Kopec CD Li J Ehrhardt D Jackson D Rhee SY Raikhel NV Citovsky V 《Plant physiology》2004,135(1):25-38
We developed a high-throughput methodology, termed fluorescent tagging of full-length proteins (FTFLP), to analyze expression patterns and subcellular localization of Arabidopsis gene products in planta. Determination of these parameters is a logical first step in functional characterization of the approximately one-third of all known Arabidopsis genes that encode novel proteins of unknown function. Our FTFLP-based approach offers two significant advantages: first, it produces internally-tagged full-length proteins that are likely to exhibit native intracellular localization, and second, it yields information about the tissue specificity of gene expression by the use of native promoters. To demonstrate how FTFLP may be used for characterization of the Arabidopsis proteome, we tagged a series of known proteins with diverse subcellular targeting patterns as well as several proteins with unknown function and unassigned subcellular localization. 相似文献
8.
Structural basis for sequential displacement of Ca(2+) by Yb(3+) in a protozoan EF-hand calcium binding protein 下载免费PDF全文
Atreya HS Mukherjee S Chary KV Lee YM Luchinat C 《Protein science : a publication of the Protein Society》2003,12(3):412-425
We have studied the displacement of Ca(2+)by the trivalent lanthanide ions (Yb(3+)) in a protozoan (Entamoeba histolytica) Ca(2+)-binding protein (EhCaBP), by NMR and thermodynamics. We have demonstrated, for the first time, how one can use in a combined fashion the utility of NMR and thermodynamics to have an insight to the relative binding specificities/affinity between Ca(2+) and Yb(3+). As revealed by the titration experiments, Yb(3+) displaces Ca(2+) from the four metal binding sites present in EhCaBP in a sequential manner. The study provides a structural origin for such a sequential Ca(2+) displacement by Yb(3+) in EhCaBP. 相似文献
9.
Crowell DN Packard CE Pierson CA Giner JL Downes BP Chary SN 《Physiologia plantarum》2003,118(1):29-37
We have identified a mutant of Arabidopsis thaliana ( lvr111 ) that exhibits a variegated phenotype, reduced isoprenoid pigmentation, and dwarfism in comparison with wild-type plants. Segregation analysis indicated that this phenotype was caused by a single, semi-dominant mutation and PCR-based marker mapping placed the mutation near position 56 on the RI map of chromosome IV. The lvr111 lesion was identified by genomic PCR and sequence analysis as a missense mutation (D306N) in the CLA1 gene (AT4g15560) and complementation analysis confirmed the allelic relationship between lvr111 and CLA1 . CLA1 encodes 1-deoxy- d -xylulose 5-phosphate synthase, which catalyses the first step of the non-mevalonate isoprenoid biosynthetic pathway. These observations demonstrate that, unlike the albinism caused by severe alleles of CLA1 , weaker alleles are associated with leaf variegation. 相似文献
10.
A novel automated approach for the sequence specific NMR assignments of 1HN, 13C, 13C, 13C/1H and 15N spins in proteins, using triple resonance experimental data, is presented. The algorithm, TATAPRO (Tracked AuTomated Assignments in Proteins) utilizes the protein primary sequence and peak lists from a set of triple resonance spectra which correlate 1HN and 15N chemical shifts with those of 13C, 13C and 13C/1H. The information derived from such correlations is used to create a `master_list' consisting of all possible sets of 1HN
i, 15Ni, 13C
i, 13C
i, 13Ci/1H
i, 13C
i–1, 13C
i–1 and 13Ci–1/ 1H
i–1 chemical shifts. On the basis of an extensive statistical analysis of 13C and 13C chemical shift data of proteins derived from the BioMagResBank (BMRB), it is shown that the 20 amino acid residues can be grouped into eight distinct categories, each of which is assigned a unique two-digit code. Such a code is used to tag individual sets of chemical shifts in the master_list and also to translate the protein primary sequence into an array called pps_array. The program then uses the master_list to search for neighbouring partners of a given amino acid residue along the polypeptide chain and sequentially assigns a maximum possible stretch of residues on either side. While doing so, each assigned residue is tracked in an array called assig_array, with the two-digit code assigned earlier. The assig_array is then mapped onto the pps_array for sequence specific resonance assignment. The program has been tested using experimental data on a calcium binding protein from Entamoeba histolytica (Eh-CaBP, 15 kDa) having substantial internal sequence homology and using published data on four other proteins in the molecular weight range of 18–42 kDa. In all the cases, nearly complete sequence specific resonance assignments (> 95%) are obtained. Furthermore, the reliability of the program has been tested by deleting sets of chemical shifts randomly from the master_list created for the test proteins. 相似文献