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21.
M Lindgren M Svensson P O Freskg?rd U Carlsson P Jonasson L G M?rtensson B H Jonsson 《Biophysical journal》1995,69(1):202-213
The spin-labeling method was used to investigate human carbonic anhydrase, HCA II, undergoing unfolding induced by guanidine-HCI (Gu-HCI). The spin-probe, N-(2,2,5,5-tetramethyl-1-yloxypyrrolidinyl-3-yl)iodoacetamide, was attached covalently to the single cysteine (position 206) in the enzyme. The electron paramagnetic resonance spectrum of the folded structure showed the characteristic slow motional spectra. When the concentration of the denaturing agent, Gu-HCI, was gradually increased, new spectral components with narrower lines evolved to give complex electron paramagnetic resonance spectra, apparently containing superimposed contributions from several components of different mobility. By a differentiation technique, it was possible to follow the relative increase of the narrow components as a function of Gu-HCI concentration. The amplitude of difference spectra versus Gu-HCI concentration showed two distinct maxima, indicating the existence of a folding intermediate state/structure. The results were found to agree with optical absorption data, which showed similar transitions at the same Gu-HCI concentrations. From line-shape simulations assuming a Brownian diffusion model, the rotational diffusion constants for the spin-label in the folded, folding intermediate, and unfolded structures were determined. The relative abundances of the three conformations in the region 0-4 M Gu-HCI were obtained by least squares fitting of the simulated spectra to the experimental ones. The folding intermediate was found to have a maximum population of 39 +/- 4% at approximately 0.7 M Gu-HCI. 相似文献
22.
Matthew Breen Gabriella Lindgren Matthew M. Binns Julianne Norman Zlaka Irvin Kevin Bell Kaj Sandberg Hans Ellegren 《Mammalian genome》1997,8(4):267-273
Twenty equine microsatellites were isolated from a genomic phage library, and their genetical and physical localization was
sought by linkage mapping and fluorescent in situ hybridization (FISH). Nineteen of the markers were found to be polymorphic
with, in most cases, heterozygosities exceeding 50%. The markers were mapped in a Swedish reference family for gene mapping,
comprising eight half-sib families from Standardbred and Icelandic horse sires. Segregation was analyzed against a set of
35 other markers typed in the pedigree. Thirteen of the microsatellites showed linkage to at least one other marker, with
a total of 21 markers being involved in these linkages. In parallel, 18 of the microsatellites could be assigned to their
chromosomal region by FISH. These assignments involved eight equine autosomes: ECA1, 2, 4, 6, 9, 10, 15, and 16. The genetical
and physical mappings revealed by this study represent a significant extension of the current knowledge of the equine genome
map.
Received: 24 September 1996 / Accepted: 1 December 1996 相似文献
23.
Several substituted phenols with antioxidant properties were potent reversible inhibitors of prostaglandin synthesis in 3T3 cell cultures. The ID50's for prostaglandin (PG) E2 synthesis in these cells were 0.1 muM for 2,6-xylenol, 5 muM for tricresol, 6 muM for p-cresol, 7 muM for o-cresol, 15 muM for 3,5-xylenol, 30 muM for m-cresol and 100 muM for phenol. The corresponding values for aspirin and indomethacin were 4 muM and 0.02 muM, respectively. The substituted phenols also inhibited serotinin release, aggregation and prostaglandin synthesis in human platelets induced by arachidonic acid but not by PGG2. 相似文献
24.
The patterns of termination of DNA replication in human embryonic MRC-5 fibroblasts at four passage levels have been examined by autoradiography. Only chromosome 9 showed statistically significant differences in the time of replication among cultures of different ages. This chromosome terminated replication earlier at later passages than at earlier passages, primarily because of differences in the time of replication of the centromere region. Because very few differences were observed at different passage levels, we conclude that changes in the order of chromosome replication are unlikely to contribute to the phenomenon of in vitro senescence. 相似文献
25.
A number of inducible plant responses are believed to contribute to disease resistance. These responses include the hypersensitive reaction, phytoalexin synthesis, and the production of chitinase, glucanase, and hydroxyproline-rich glycoproteins. Because of the coordinate induction of these responses, it has been difficult to determine whether they are functional defense responses, and if they are, how they specifically contribute to disease resistance. Recent developments in molecular biology have provided experimental techniques that will reveal the specific contribution of each response to disease resistance. In this paper, we describe a strategy to determine if the hypersensitive reaction is a functional plant defense mechanism. 相似文献
26.
Inhibition of transplasma membrane electron transport by monoclonal antibodies to the transferrin receptor 总被引:1,自引:0,他引:1
W Toole-Simms I L Sun W P Faulk H L?w A Lindgren F L Crane D J Morré 《Biochemical and biophysical research communications》1991,176(3):1437-1442
Reduction of iron in diferric transferrin is inhibited by monoclonal antibodies to the transferrin receptor which bind at sites other than the high affinity transferrin binding site. These antibodies include B3/25, GB16 and GB22. Two antibodies which bind at the high affinity site for transferrin, 42/6 and GB18, do not inhibit iron reduction by transplasma membrane electron transport. The results are consistent with the proposal that differric transferrin reduction or stimulation of transmembrane NADH oxidase activity involves a site different from the high affinity diferric transferrin binding site. A synergistic action of antibodies with epitopes at the tight binding site involved in iron uptake and the antibodies which inhibit electron transport, B3/25 and GB16, can explain the increased inhibition of growth observed when both 42/6 and B3/25 are added to proliferating cells. 相似文献
27.
Clark A. Lindgren Dennis J. Paulson Michael F. Shanahan 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1982,721(4):385-393
The usefulness of isolated Ca2+-tolerant myocytes as a cellular model system for investigating modulation of monosaccharide transport by insulin was investigated. We have found that the isolation technique described by Haworth et al. (Haworth, R.A., Hunter, D.R. and Berkoff, H.A. (1980) J. Mol. Cell. Cardiol. 12, 715–724), with some minor modifications, consistently gave the highest yield of quiescent, rod-shaped myocytes which maintained their integrity in the presence of 2 mM calcium. Using 3-O-methylglucose, a non-metabolized sugar, transport was shown to possess saturability, substrate stereospecificity, competition and countertransport; all of which have been thoroughly established for d-glucose transport in other systems. The apparent Km of transport ranged from 2.3 to 3.5 mM. Insulin (10 nM) caused a small but significant increase in Km and a 2–3-fold increase in Vmax. These results suggest that this myocyte preparation will provide a useful model for studying the transport-related effects of insulin as well as current hypotheses regarding the mechanism of insulin modulation of transport at the cellular level. 相似文献
28.
Anders
lund Hans Kindahl Ernst Oliw ke Lindgren Jan Bertil Larsson 《Prostaglandins & other lipid mediators》1980,19(5):791-803
Abortion or delivery were induced by extra-amniotic instillation of Rivanol during the second trimester in twelve patients and during the third trimester in two patients with fetal death and one patient with fetal acrania. Serial sampling of amniotic fluid was performed through a transabdominal catheter and the levels of free arachidonic acid (AA), prostaglandin F2α (PGF2α), prostaglandin E2 (PGE2), 6-keto-prostaglandin F1α (6-keto-PGF1α) and thromboxane B2 (TXB2) were determined. The levels of AA, PGF2α, PGE2, 6-keto-PGF1α and TXB2 in amniotic fluid increased significantly during induction with the exception of AA in fetal death which was high and remained constant during induction. Furthermore, PGF2α, 6-keto-PGF1α and TXB2 were all significantly correlated to AA.These observations suggested that free AA is released during Rivanol-induction of abortion and labour giving an increased synthesis of PGF2α, PGE2 prostacyclin and thromboxane A2 in the fetal membranes and the decidua but not in the fetus. This increase might be relevant for the initiation and progress of abortion and labour in these patients. 相似文献
29.
High-molecular-weight penicillin-binding proteins from membranes of bacilli 总被引:3,自引:3,他引:0 下载免费PDF全文
Mixtures of high-molecular-weight, cephalosporin-sensitive penicillin-binding proteins (PBPs) can be purified from Bacillus subtilis membranes by cephalosporin affinity chromatography (G. Kleppe and J. L. Strominger, J. Biol. Chem. 254:4856-4862, 1979). By appropriate modification of this technique, B. subtilis PBP 1 was purified to homogeneity, and a mixture of Bacillus stearothermophilus PBPs 1, 2, and 4 was isolated. [14C]penicillin-PBP complexes of high-molecular-weight PBPs purified from membranes of these two bacilli, after denaturation, were found to have chemical reactivities typical of the penicilloyl-serine derivative formed by D-alanine carboxypeptidase from B. stearothermophilus. Although enzymatic activity catalyzed by these and several other high-molecular-weight PBPs from gram-positive organisms has not been detected with cell wall-related substrates, a slow, enzymatic acylation of B. subtilis PBPs 1, 2ab, and 4 by [14C]-diacetyl-L-lysyl-D-alanyl-D-lactate was demonstrated. Further study is necessary to clarify the physiological relevance of the slow acylation by this analog of a natural cell wall biosynthetic intermediate. 相似文献
30.
In pleiotropic negative glycerol utilization mutants (GlpPI mutants) of Bacillus subitilis, glycerol kinase and sn-glycerol 3-phosphate (G3P) dehydrogenase are noninducible. GlpPI mutants also fail to take up exogenous [14C]G3P. To study the regulation of the glp system in B. subtilis phenotypically, Glp+ revertants were isolated from GlpPI mutants. Four classes of revertants were identified: phenotypically, wild type; R1 type, which contains an informational suppressor, R2 type, which produced G3P dehydrogenase constitutively; and R3 type, with a temperature-sensitive Glp phenotype producing G3P dehydrogenase constitutively at permissive temperature (32 degrees C). The properties of the revertants indicate that the glpPI locus codes for a protein with a positive regulatory function. 相似文献