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31.
Ryan Davis David Bienvenue Sabina I. Swierczek Danuta M. Gilner Lakshman Rajagopal Brian Bennett Richard C. Holz 《Journal of biological inorganic chemistry》2006,11(2):206-216
Glutamate-134 (E134) is proposed to act as the general acid/base during the hydrolysis reaction catalyzed by the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae. To date, no direct evidence has been reported for the role of E134 during catalytic turnover by DapE. In order to elucidate
the catalytic role of E134, altered DapE enzymes were prepared in which E134 was substituted with an alanine and an aspartate
residue. The Michaelis constant (K
m) does not change upon substitution with aspartate but the rate of the reaction changes drastically in the following order:
glutamate (100% activity), aspartate (0.09%), and alanine (0%). Examination of the pH dependence of the kinetic constants
k
cat and K
m for E134D-DapE revealed ionizations at pH 6.4, 7.4, and approximately 9.7. Isothermal titration calorimetry experiments revealed
a significant weakening in metal K
d values of E134D-DapE. D134 and A134 perturb the second divalent metal binding site significantly more than the first, but
both altered enzymes can still bind two divalent metal ions. Structural perturbations of the dinuclear active site of DapE
were also examined for two E134-substituted forms, namely E134D-DapE and E134A-DapE, by UV–vis and electron paramagnetic resonance
(EPR) spectroscopy. UV–vis spectroscopy of Co(II)-substituted E134D-DapE and E134A-DapE did not reveal any significant changes
in the electronic absorption spectra, suggesting that both Co(II) ions in E134D-DapE and E134A-DapE reside in distorted trigonal
bipyramidal coordination geometries. EPR spectra of [Co_(E134D-DapE)] and [Co_(E1341A-DapE] are similar to those observed
for [CoCo(DapE)] and somewhat similar to the spectrum of [Co(H2O)6]2+ which typically exhibit E/D values of approximately 0.1. Computer simulation returned an axial g-tensor with g
(x,y)=2.24 and E/D=0.07; g
z
was only poorly determined, but was estimated as 2.5–2.6. Upon the addition of a second Co(II) ion to [Co_(E134D-DapE)] and
[Co_(E134A-DapE)], a broad axial signal was observed; however, no signals were observed with B
0||B
1 (“parallel mode”). On the basis of these data, E134 is intrinsically involved in the hydrolysis reaction catalyzed by DapE
and likely plays the role of a general acid and base. 相似文献
32.
33.
Catechol 2, 3-dioxygenase is present in several types of bacteria and undergoes degradation of environmental pollutants through
an important key biochemical pathways. Specifically, this enzyme cleaves aromatic rings of several environmental pollutants such
as toluene, xylene, naphthalene and biphenyl derivatives. Hence, the importance of Catechol 2, 3-dioxygenase and its role in the
degradation of environmental pollutants made us to predict the three-dimensional structure of Catechol 2, 3-dioxygenase from
Burkholderia cepacia. The 10ns molecular dynamics simulation was carried out to check the stability of the modeled Catechol 2, 3-
dioxygenase. The results show that the model was energetically stable, and it attains their equilibrium within 2000 ps of production
MD run. The docking of various petroleum hydrocarbons into the Catechol 2,3-dioxygenase reveals that the benzene, O-xylene,
Toluene, Fluorene, Naphthalene, Carbazol, Pyrene, Dibenzothiophene, Anthracene, Phenanthrene, Biphenyl makes strong
hydrogen bond and Van der waals interaction with the active site residues of H150, L152, W198, H206, H220, H252, I254, T255,
Y261, E271, L276 and F309. Free energy of binding and estimated inhibition constant of these compounds demonstrates that they
are energetically stable in their binding cavity. Chrysene shows positive energy of binding in the active site atom of Fe. Except
Pyrene all the substrates made close contact with Fe atom by the distance ranges from 1.67 to 2.43 Å. In addition to that, the above
mentioned substrate except pyrene all other made π-π stacking interaction with H252 by the distance ranges from 3.40 to 3.90 Å.
All these docking results reveal that, except Chrysene all other substrate has good free energy of binding to hold enough in the
active site and makes strong VdW interaction with Catechol-2,3-dioxygenase. These results suggest that, the enzyme is capable of
catalyzing the above-mentioned substrate. 相似文献
34.
35.
36.
Luke B Chenoweth Simon M Tierney Jaclyn A Smith Steven JB Cooper Michael P Schwarz 《BMC evolutionary biology》2007,7(1):246
Background
The major lineages of eusocial insects, the ants, termites, stingless bees, honeybees and vespid wasps, all have ancient origins (≥ 65 mya) with no reversions to solitary behaviour. This has prompted the notion of a 'point of no return' whereby the evolutionary elaboration and integration of behavioural, genetic and morphological traits over a very long period of time leads to a situation where reversion to solitary living is no longer an evolutionary option. 相似文献37.
38.
Integrative analyses of genetic variation in enzyme activities of primary carbohydrate metabolism reveal distinct modes of regulation in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>
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39.
Kutryk MJ Wardeh AJ Knook AH Foley DP Giessen WJ Hamburger JN Brand Mv Feyter PJ Becker GJ Serruys PW 《International journal of cardiovascular interventions》1999,2(3):163-169
BACKGROUND: Coronary stents have been used with increasing frequency and in increasingly complex coronary disease. A new 316 LVM stainless steel coronary stent, the R Stent, has been designed to provide maximum flexibility for tracking and high radial strength post-deployment. PURPOSE: To assess the clinical feasibility of the R Stent in a tertiary referral population of patients with coronary heart disease. Specific objectives are to assess the R Stent's deployment success, angiographic and procedural success (<20% residual stenosis and >TIMI 2 flow), safety (absence of complications), and 30-day clinical success (angiographic/procedural success plus no major adverse coronary events). METHODS: Between April and November 1998, stent deployment was attempted in 27 patients with stable (46%) or unstable (54%) angina pectoris who qualified for percutaneous transluminal coronary angioplasty. Eighty per cent of patients had a pre-existing history of myocardial infarction, coronary bypass surgery or percutaneous transluminal coronary angioplasty, and several of the lesions were anatomically complex (totally occluded, n 32; thrombus present, n 32; heavily calcified, n 33; ostial, n 31; >20 mm long, n 39; angulation >45 degrees, n 37). Lesions in aortocoronary saphenous vein grafts were excluded. Adjunctive medical management included intraprocedural aspirin and heparin and post-procedural aspirin and ticlopidine. After deployment, patients were followed up in the hospital and at 30 days post procedure. RESULTS: Stent deployment was achieved in 32 of 33 attempts (26 of 27 patients). There was one deployment failure in a long, calcified ostial and proximal left coronary lesion. In the 26 successful deployments, TIMI 3 flow was achieved. One other patient experienced a painless increase in creatine kinase to 375 (CK-MB of 59) at 12 h without ECG changes. At 30 days, there were no deaths, no myocardial infarctions, no subacute thromboses, no repeat interventions, no bypass surgeries and no bleeding complications. Only the patient with post-procedural CK-MB elevation experience recurrence of CCS class 2 angina within the 30 days. CONCLUSION: The R Stent is a promising new device for the treatment of complex coronary heart disease. A larger, more broadly-based study is warranted. 相似文献
40.