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1.
H G Bull N A Thornberry M H Cordes A A Patchett E H Cordes 《The Journal of biological chemistry》1985,260(5):2952-2962
Two novel peptide analogs, N alpha-[(S)-1-carboxy-3-phenylpropyl]L-alanyl-L-proline and the corresponding L-lysyl-L-proline derivative, have been demonstrated to be potent competitive inhibitors of purified rabbit lung angiotensin-converting enzyme: Ki = 2 and 1 X 10(-10) M, respectively, at pH 7.5, 25 degrees C, and 0.3 M chloride ion. Second-order rate constants for addition of these inhibitors to enzyme under the same conditions are in the range 1-2 X 10(6) M-1 s-1; first-order rate constants for dissociation of the EI complexes are in the range 1-4 X 10(-4) s-1. The association rate constants are similar to those measured for D-3-mercapto-2-methylpropanoyl-L-proline, captopril, but the dissociation rate constants are severalfold slower and account for the higher affinity of these inhibitors for the enzyme. The dissociation constant for the EI complex containing N alpha-[(S)-1-carboxy-3-phenylpropyl]L-alanyl-L-proline is pH-dependent, and reaches a minimum at approximately pH 6: Ki = 4 +/- 1 X 10(-11) M. The pH dependence is consistent either with a model for which the protonation state of the secondary nitrogen atom in the inhibitor determines binding affinity, or one for which ionizations on the enzyme alone influence affinity for these inhibitors. The affinity of this inhibitor for the zinc-free apoenzyme is 2 X 10(4) times less than for the zinc-free apoenzyme is 2 X 10(4) times less than that for the holoenzyme. If considered as a "collected product" inhibitor, N alpha-[(S)-1-carboxy-3-phenylpropyl]L-alanyl-L-proline appears to derive an additional factor of 375 M in its affinity for the enzyme compared to that of the two products of its hypothetical hydrolysis, a consequence of favorable entropy effects. 相似文献
2.
Respiratory chain phosphorylation has been investigated in the methylotrophic bacterium Methylophilus methylotrophus following the addition of oxidisable substrates to aerobic, whole cell suspensions. Initial-rate experiments showed that ATP synthesis occurred at the overall expense of AMP and inorganic phosphate via the sequential action of the ATP phosphohydrolase and adenylate kinase; some of the nascent ATP was rapidly used to synthesis nonadenine nucleoside triphosphates. After being corrected for ATP turnover, Pi/O quotients of 0.46 to 0.54, 0.77 and 1.37 nmol/ng-atom O were obtained for the oxidation of methanol dehydrogenase-linked substrates (methanol, ethanol and acetaldehyde), duroquinol and formate (NAD+-linked) respectively. These values were proportional to the H+/O and/or K+/O quotients exhibited by these substrates, and yielded an average H+/ATP (H+/Pi) quotient of 4.2 ng-ion H+/nmol. Steady-state experiments showed that the extent of cellular energisation varied with the respiration rate but was always in the order methanol > duroquinol > acetaldehyde, thus indicating that under these longer-term conditions methanol was completely oxidised to yield PQQH2 and 2NAD(P)H. These results are discussed in terms of the various reactions which lead to the generation or utilisation of the protonmotive force in this organism.Abbreviations FCCP
carbonylcyanide p-trifluoromethyxyphenyl-hydrazone
-
bulk phase, transmembrane electrochemical potential difference of protons (
)
- pH
bulk phase, transmembrane pH difference (pHin–pHout)
-
bulk phase, transmembrane electrical potential difference (in - out)
- [P]
concentration of anhydride phosphate bonds in adenine nucleotides (2[ATP]+[ADP])
- FPLC
fast protein liquid chromatography
- PQQ
pyrroloquinoline quinone
- Gp
phosphorylation potential 相似文献
3.
Uptake of [14C]glycine-betaine by Listeria monocytogenes was stimulated by NaCl with optimal stimulation at 0.4–0.5 M. The glycine-betaine transport system had a K
m of 22 M and a V
max of 11.7 nmol-1 min-1 mg-1 protein when grown in the absence of NaCl. When grown in the presence of 0.8 M NaCl the V
max increased to 27.0 nmol-1 min-1 mg-1 protein in 0.8 M NaCl. At NaCl concentrations above 0.5 M the uptake rate of glycine-betaine was reduced. Measurement of intracellular K+ concentrations and fluorescent dye quenching indicated that higher NaCl concentrations also led to a decrease in the electrochemical potential difference across the cytoplasmic membrane. Uptake of glycine was also observed, but this was not stimulated by NaCl. 相似文献
4.
The effect of EDTA and related chelating agents on the oxidation of methanol by the methylotrophic bacterium, Methylophilus methylotrophus 总被引:3,自引:0,他引:3
M A Carver K M Humphrey R A Patchett C W Jones 《European journal of biochemistry》1984,138(3):611-615
The effects of EDTA and related metal-chelating agents on the respiratory system of the methylotrophic bacterium Methylophilus methylotrophus have been investigated. EDTA completely inhibited whole cell methanol oxidase activity and concomitantly decreased the aerobic steady-state reduction level of cytochrome c, but only partially inhibited methanol dehydrogenase activity. Analysis of the inhibition kinetics of EDTA and other chelating agents on methanol oxidase activity indicated that they were effective in the order CDTA greater than EDTA greater than HEDTA greater than EGTA greater than EDDA, and that they inhibited in an uncompetitive manner. Inhibition by EDTA varied as a function of the ambient cell mass in the assay, and could be partly reversed by the addition of divalent cations. EDTA had no effect on the activity of solubilised methanol dehydrogenase. These and other results indicate that EDTA binds a divalent metal ion, probably Mg2+, which is involved in the functional association of methanol dehydrogenase with the respiratory membrane. This concept is discussed in terms of the electron transfer properties and spatial organisation of the terminal respiratory chain of M. methylotrophus. 相似文献
5.
6.
The concentrations of intracellular solutes in Listeria monocytogenes were examined in cells grown at various concentrations of NaCl. At 5% NaCl, cells contained elevated concentrations of potassium and glycine betaine compared with concentrations in cells grown without NaCl. At 7.5% NaCl, cells contained increased concentrations of K+, glycine betaine, glycine, alanine, and proline. Only glycine betaine, choline, or glycine promoted growth on a solidified defined medium containing 4% NaCl; there was no growth at higher concentrations of NaCl in the defined medium. 相似文献
7.
S Patchett S Beattie E Leen C Keane C O'Morain 《BMJ (Clinical research ed.)》1991,303(6812):1238-1240
OBJECTIVE--To examine the effect of eradication of Helicobacter pylori on symptoms of non-ulcer dyspepsia. DESIGN--Four week prospective study. SETTING--One hospital outpatient and endoscopy department. PATIENTS--90 adults with persistent symptoms typical of non-ulcer dyspepsia but no clinical or endoscopic evidence of other peptic, biliary, pancreatic, or malignant disease; all had histological and microbiological evidence of infection with H pylori. 83 patients completed the treatment regimen. INTERVENTION--Colloidal bismuth subcitrate 120 mg four times a day for four weeks (27 patients); metronidazole 400 mg and amoxycillin 500 mg each three times a day for one week (27); and bismuth subcitrate 120 mg four times a day for four weeks, metronidazole 400 mg three times a day for one week, plus amoxycillin 500 mg three times a day for the first week (29). MAIN OUTCOME MEASURES--Change in symptom scores determined with questionnaire; histological evidence of gastritis and microbiological evidence of presence of H pylori in biopsy specimens. RESULTS--Overall, H pylori was eradicated in 41 (49%) patients. Although gastritis scores improved significantly in only patients in whom H pylori had been eradicated (from 1.56 to 0.61, p less than 0.01 v from 1.83 to 1.07, p = 0.52) mean symptom scores after treatment were similar in patients in whom H pylori had or had not been eradicated (3.0 v 2.3, NS). Similarly the mean symptom score improved whether or not gastritis improved (2.8 v 3.1 respectively, p = 0.72). The observations were similar for treatment groups analysed individually. CONCLUSION--Antral infection with the organism does not seem to have an important aetiological role in non-ulcer dyspepsia short term. 相似文献
8.
M.J. Payne Shona Campbell R.A. Patchett R.G. Kroll 《Journal of applied microbiology》1992,73(1):41-52
Lectins from Helix pomatia, Canavalia ensiformis, Agaricus bisporus and Triticum vulgaris agglutinated cultures of Staphylococcus aureus, Escherichia coli, Listeria and Salmonella spp. This agglutination was specific as it was inhibited (except with A. bisporus lectin) by the competing sugar substrates. The ability of three of these lectins, immobilized on a variety of supports, to separate these micro-organisms from pure cultures was investigated. Immobilization of the lectins on magnetic microspheres was the most effective method. Immobilized T. vulgaris lectin bound 87–100% of cells from cultures of L. monocytogenes , 80–100% of Staph. aureus , 33–45% of Salmonella spp. and 42–77% of E. coli. The A. bisporus lectin bound 31–63% of cells in cultures of L. monocytogenes , 83% of Staph. aureus but only 3–5% of the salmonella cells. Similarly H. pomatia lectin bound >92% of Staph. aureus and 64% of L. monocytogenes cells but was poor at binding the Gram-negative organisms. This preference for binding Gram-positive organisms was confirmed when mixed cultures were studied. The T. vulgaris lectin was effective in removing L. monocytogenes (43%) and Staph. aureus (26%) from diluted milk and Salmonella (31–54%) from raw egg. Agaricus bisporus lectin removed L. monocytogenes from undiluted milk (10–47%) or ground beef (32–50%). 相似文献
9.
Differential response of cycling and noncycling cells to inducers of DNA synthesis and mitosis 总被引:1,自引:0,他引:1 下载免费PDF全文
The objective of this study was to determine whether cells in G(0) phase are functionally distinct from those in G(1) with regard to their ability to respond to the inducers of DNA synthesis and to retard the cell cycle traverse of the G(2) component after fusion. Synchronized populations of HeLa cells in G(1) and human diploid fibroblasts in G(1) and G(0) phases were separately fused using UV-inactivated Sendai virus with HeLa cells prelabeled with [(3)H]ThdR and synchronized in S or G(2) phases. The kinetics of initiation of DNA synthesis in the nuclei of G(0) and G(1) cells residing in G(0)/S and G(1)/S dikaryons, respectively, were studied as a function of time after fusion. In the G(0)/G(2) and G(1)/G(2) fusions, the rate of entry into mitosis of the heterophasic binucleate cells was monitored in the presence of Colcemid. The effects of protein synthesis inhibition in the G(1) cells, and the UV irradiation of G(0) cells before fusion, on the rate of entry of the G(2) component into mitosis were also studied. The results of this study indicate that DNA synthesis can be induced in G(0)nuclei after fusion between G(0)- and S-phase cells, but G(0) nuclei are much slower than G(1) nuclei in responding to the inducers of DNA synthesis because the chromatin of G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells differ from G(1) cells with regard to their effects on the cell cycle progression of the G(2) nucleus into mitosis. This difference between G(0) and G(1) cells appears to depend on certain factors, probably nonhistone proteins, present in G(1) cells but absent in G(0) cells. These factors can be induced in G(0) cells by UV irradiation and inhibited in G(1) cells by cycloheximide treatment. 相似文献
10.
Danilo ML Prado Fabiana B Benatti Ana L de Sá-Pinto Ana P Hayashi Bruno Gualano Rosa MR Pereira Adriana ME Sallum Eloisa Bonfá Clovis A Silva Hamilton Roschel 《Arthritis research & therapy》2013,15(2):R46