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141.
Asensio JL; Canada FJ; Bruix M; Gonzalez C; Khiar N; Rodriguez-Romero A; Jimenez-Barbero J 《Glycobiology》1998,8(6):569-577
The specific interaction of hevein with GlcNAc-containing oligosaccharides
has been analyzed by1H-NMR spectroscopy. The association constants for the
binding of hevein to a variety of ligands have been estimated from1H-NMR
titration experiments. The association constants increase in the order
GlcNAc-alpha(1-->6)-Man < GlcNAc < benzyl-beta-GlcNAc <
p-nitrophenyl-beta-GlcNAc < chitobiose < p-
nitrophenyl-beta-chitobioside < methyl-beta-chitobioside <
chitotriose. Entropy and enthalpy of binding for different complexes have
been obtained from van't Hoff analysis. The driving force for the binding
process is provided by a negative DeltaH0which is partially compensated by
negative DeltaS0. These negative signs indicate that hydrogen bonding and
van der Waals forces are the major interactions stabilizing the complex.
NOESY NMR experiments in water solution provided 475 accurate protein
proton-proton distance constraints after employing the MARDIGRAS program.
In addition, 15 unambiguous protein/carbohydrate NOEs were detected. All
the experimental constraints were used in a refinement protocol including
restrained molecular dynamics in order to determine the highly refined
solution conformation of this protein- carbohydrate complex. With regard to
the NMR structure of the free protein, no important changes in the protein
nOe's were observed, indicating that carbohydrate-induced conformational
changes are small. The average backbone rmsd of the 20 refined structures
was 0.055 nm, while the heavy atom rmsd was 0.116 nm. It can be deduced
that both hydrogen bonds and van der Waals contacts confer stability to the
complex. A comparison of the three-dimensional structure of hevein in
solution to those reported for wheat germ agglutinin (WGA) and hevein
itself in the solid state has also been performed. The polypeptide
conformation has also been compared to the NMR-derived structure of a
smaller antifungical peptide, Ac-AMP2.
相似文献
142.
IV Zlatkin M Schneider FJ de Bruijn LJ Forney PhD 《Journal of industrial microbiology & biotechnology》1996,17(3-4):219-227
Culturable bacteria from the deep subsurface (179 m) at Cerro Negro, New Mexico were isolated and characterized. The average number of viable aerobic bacteria was estimated to be 5×105g–1 of sediment, but only about 0.1% of these could be recovered on agar medium when incubated under aerobic conditions. Of 158 strains isolated from this depth, 92 were characterized by cellular fatty acid profiles (FAME), 36 by analysis of partial 16S rDNA sequences, and 44 by rep-PCR genome fingerprint analysis using three different sets of oligonucleotide primers (REP, BOX, or ERIC). These analyses showed the majority of isolates (67%) were Gram-positive bacteria and primarily members of genera with a high %G+C DNA. The remaining isolates were -subdivisionProteobacteria (19%) and members of the flavobacteria group (14%). The diversity indices based on these different methods of characterization were very high suggesting this subsurface habitat harbors a highly diverse microbial community. 相似文献
143.
Phylogenetic reconstruction of the Drosophila obscura group, on the basis of mitochondrial DNA 总被引:2,自引:0,他引:2
We have constructed restriction-site maps of the mtDNAs in 13 species and
one subspecies of the Drosophila obscura group. The traditional division of
this group into two subgroups (affinis and obscura) does not correspond to
the phylogeny of the group, which shows two well- defined clusters (the
Nearctic affinis and pseudoobscura subgroups) plus a very heterogeneous set
of anciently diverged species (the Palearctic obscura subgroup). The mtDNA
of Drosophila exhibits a tendency to evolve toward high A+T values. This
leads to a "saturation" effect that (1) begets an apparent decrease in the
rate of evolution as the time since the divergence of taxa increases and
(2) reduces the value that mtDNA restriction analysis has for the
phylogenetic reconstruction of Drosophila species that are not closely
related.
相似文献
144.
Changes in ionized calcium were studied in axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy. Absorption changes measured in situ were calibrated in vitro with media of ionic composition similar to axoplasm containing CaEGTA buffers. Calcium loads of 50-2,500 μmol/kg axoplasm were induced by microinjection, by stimulation in 112 mM Ca seawater, or by soaking in choline saline with 1-10 mM Ca. Over this range of calcium loading of intact axoplasm, the ionized calcium in the axoplasm rose about 0.6 nM/μM load. Similar loading in axons preteated with carbonyl cyanide 4- trifluoromethoxyphenylhydrazone (FCCP) to inhibit the mitochondrial proton gradient increased ionized calcium by 5-7 percent of the imposed load, i.e. 93-95 percent of the calcium load was buffered by a process insensitive to FCCP. This FCCP- insensitive buffer system was not saturated by the largest calcium loads imposed, indicating a capacity of at least several millimolar. Treatment of previously loaded axons with FCCP or apyrase plus cyanide produced rises in ionized calcium which could be correlated with the extent of the load. Analysis of results indicated that, whereas only 6 percent of the endogenous calcium in fresh axons is stored in the FCCP-sensitive (presumably mitochondrial) buffer system, about 30 percent of an imposed exogenous load in the range of 50-2,500 μM is taken up by this system. 相似文献
145.
Additional electrocardiocardiographic chest leads (V7, V8, and V9) were used in 117 persons consecutively admitted to a coronary care unit. Among the 46 (39%) with a proven acute myocardial infarction the electrocardiograms (ECGs) of 9 (20%) showed ST-segment elevation or abnormal Q-waves, or both, in the three additional leads. In six of the nine, such changes were associated with signs of anterolateral or inferior wall infarction (in three each) on the standard 12-lead ECG, but in the other three (7% of the 46) electrocardiographic changes diagnostic of acute myocardial infarction were found only on the additional chest leads; the last three had characteristic changes in serum enzyme concentrations. This study showed that additional chest leads are helpful in detecting myocardial injury of necrosis in areas of the heart not properly reflected on the standard 12-lead ECG. 相似文献
146.
H Barahona M D Daniel S L Katz J K Ingalls L V Melendez N W King 《Laboratory animal science》1975,25(6):735-740
A viral agent was isolated from ground squirrel primary kidney cultures which presented a spontaneous cell layer alteration. The cultural, morphologic, and physico-chemical characteristics of the agent indicated that it belongs in the herpesvirus group. The isolate presented a narrow in vitro cell host range, growing best in marmoset monkey, owl monkey, rabbit, and hamster kidney cultures and poorly in Vero and dog fetal lung cells. The agent is readily released from infected cells, a fact which indicates that it is a cell-free virus. Good plaque formation was observed only in marmoset monkey kidney monolayers. The virus was not neutralized by antisera against other herpesviruses with the exception of a partial 1-way cross-neutralization between ground squirrel agent and Herpesvirus saguinus antisera. All these characteristics indicate that this virus is likely a new member of the herpesvirus family. 相似文献
147.
The left ventricular function of 30 patients with coronary artery disease and 11 control subjects was studied by electrocardiography gated cardiac blood pool scintigraphy as the participants lay on their backs and either rested or exercised on a cycle ergometer at graded levels on intensity. The control subject showed a progressive increase in ejection fraction from rest (51% +/- 7%) to intermediate (56% +/- 10%, P less than 0.05) and maximum levels of exercise (64% +/- 10%, P less than 0.001). All the patients showed a decrease in ejection fraction from rest (42% +/- 16%) to their maximal level of exercise (36% +/- 11%, P less than 0.001). However, the response of some of the patients to intermediate exercise ranged from a decrease or no change to an increase in ejection fraction. Thus, exercise at maximal intensity is necessary to induce the left ventricular dysfunction that is diagnostic of coronary artery disease. 相似文献
148.
149.