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排序方式: 共有178条查询结果,搜索用时 62 毫秒
1.
L V Karabashian S A Agadzhanian K V Danoian R A Kazarian 《Bioorganicheskaia khimiia》1988,14(11):1502-1508
The urea-induced inactivation and dissociation of catalytically active hexamer of glutamate dehydrogenase (L-glutamate-NAD(P)-oxidoreductase, EC 1.4.1.3) from bovine liver were studied using radioactive phosphopyridoxyl derivative of the enzyme immobilized on cyanogen bromide-activated Sepharose CL-4B. It is shown that at neutral pH (7.0-7.8) urea causes dissociation of glutamate dehydrogenase to directly yield catalytically inactive immobilized monomers rather than hexamer's stable fragments at the same time. At pH 8.9 or 5.6 the urea-induced is accompanied by the formation of conformationally stable immobilized dimers or trimers, respectively. The trimers are catalytically active, whereas the dimers did not exhibit any enzymatic activity. The data obtained led to suggestion that the hexamer consists of three either equivalent dimers (3 alpha 2) or of two equivalent trimers (2 alpha 3). 相似文献
2.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
3.
4.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献
5.
The simulation of long-term creep response behavior, observed on 54 Rhesus monkey intervertebral joints subjected to a constant axial compressive stress, is attempted by two- and three-parameter-solid models utilizing the Burns- Kaleps 'exact analysis scheme'. Model parameters identified by the analysis of each specimen's experimental strain data were optimized via a computer program and the mechanical properties (Young's moduli and the viscosity coefficient) appropriate to each model were calculated for individual spinal segments. Simulation results for the two-parameter-solid (one- Kelvin -unit) model demonstrate its general ineptness in predicting the observed strain-time behavior of normal spinal sements . The three-parameter-solid model yielded excellent results in the simulation of observed spinal segment compressive creep phenomena. It produced an average error between the model predicted and experimental strain values that ranged from a low of 0.4000% to a high of 3.290% for the 54 Rhesus monkey intervertebral joints, with a collective average error for all specimens of only 1.363%. 相似文献
6.
The creep response phenomena observed on 47 human intervertebral discs subjected to a constant axial compressive stress was analytically studied by two-, three- and four-parameter-solid models employing the Burns- Kaleps 'exact analysis scheme'. The mechanical properties (Young's moduli and viscosity coefficients) associated with each model were calculated for each of the 47 disks, with superior results obtained for the latter two models. Results for the two-parameter-solid model suggest its possible usefulness in simulating creep response that is characteristic of disk degeneration. Results for the three- and four-parameter-solid models were excellent, with an average error for the model predicted strain, epsilon(ti)cal, values from the experimentally measured, epsilon(ti)exp, values of 2.314% for the former model and 4.446% for the latter model on the 47 human spinal segments analyzed. The three-parameter-solid model was most sensitive in its predictability of strain behavior for ti greater than 1 min; whereas the four-parameter-solid model demonstrated greater simulation sensitivity in the 0 less than ti less than or equal to 1 min range. 相似文献
7.
8.
L S Gambarian A G Kazarian A A Garibian 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1975,25(5):953-961
Bilateral ablation of the putamen results in temporary disappearance of natural as well as artificial conditioned motor reflexes in cats. Further training is necessary for their reestablishment. Restored conditioned reflexes appear with a long latency. After partial bilateral ablation of the putamen, animals that have been trained not only to press a pedal, but also to make a choice between a right or left feeding tray, lose the latter ability. After the reestablishment of conditioned reflexes, the animal makes a correct choice of side only in 68--70% of cases. After total bilateral ablation of the putamen the animals lose artificial conditioned reflexes. The results suggest that the putamen has a close relation to the mechanisms of learning and memory. 相似文献
9.
ERIC S. BONO PATRICK SMOLINSKI AL CASAGRANDA JUNDE XU 《Computer methods in biomechanics and biomedical engineering》2013,16(2):125-131
The Shear-slip Mesh Update Method (SSMUM) is being used in flow simulations involving large but regular displacements of one or more boundaries of the computational domain. We follow up the earlier discussion of the method with notes on practical implementation aspects. In order to establish a benchmark problem for this class of flow problems, we define and report results from a two-dimensional viscous flow around a rotating stirrer in a square chamber. The application potential of the method is demonstrated in the context of biomedical design problem, as we perform an analysis of blood flow in a centrifugal left ventricular assist device, or blood pump, which involves a rotating impeller in a non-axisymmetric housing. 相似文献
10.