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71.
Rogers MS Hurtado-Guerrero R Firbank SJ Halcrow MA Dooley DM Phillips SE Knowles PF McPherson MJ 《Biochemistry》2008,47(39):10428-10439
Galactose oxidase (GO) belongs to a class of proteins that self-catalyze assembly of their redox-active cofactors from active site amino acids. Generation of enzymatically active GO appears to require at least four sequential post-translational modifications: cleavage of a secretion signal sequence, copper-dependent cleavage of an N-terminal pro sequence, copper-dependent formation of a C228-Y272 thioether bond, and generation of the Y272 radical. The last two processes were investigated using a truncated protein (termed premat-GO) lacking the pro sequence and purified under copper-free conditions. Reactions of premat-GO with Cu(II) were investigated using optical, EPR, and resonance Raman spectroscopy, SDS-PAGE, and X-ray crystallography. Premat-GO reacted anaerobically with excess Cu(II) to efficiently form the thioether bond but not the Y272 radical. A potential C228-copper coordinated intermediate (lambda max = 406 nm) in the processing reaction, which had not yet formed the C228-Y272 cross-link, was identified from the absorption spectrum. A copper-thiolate protein complex, with copper coordinated to C228, H496, and H581, was also observed in a 3 min anaerobic soak by X-ray crystallography, whereas a 24 h soak revealed the C228-Y272 thioether bond. In solution, addition of oxygenated buffer to premat-GO preincubated with excess Cu(II) generated the Y272 radical state. On the basis of these data, a mechanism for the formation of the C228-Y272 bond and tyrosyl radical generation is proposed. The 406 nm complex is demonstrated to be a catalytically competent processing intermediate under anaerobic conditions. We propose a potential mechanism which is in common with aerobic processing by Cu(II) until the step at which the second electron acceptor is required. 相似文献
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Zehava Grossman Jonathan M. Schapiro Itzchak Levy Daniel Elbirt Michal Chowers Klaris Riesenberg Karen Olstein-Pops Eduardo Shahar Valery Istomin Ilan Asher Bat-Sheva Gottessman Yonat Shemer Hila Elinav Gamal Hassoun Shira Rosenberg Diana Averbuch Keren Machleb-Guri Zipi Kra-Oz Sara Radian-Sade Hagit Rudich Daniela Ram Shlomo Maayan Nancy Agmon-Levin Zev Sthoeger 《PloS one》2014,9(1)
Background
Analysis of potentially different impact of Lopinavir/Ritonavir (LPV/r) on non-B subtypes is confounded by dissimilarities in the conditions existing in different countries. We retrospectively compared its impact on populations infected with subtypes B and C in Israel, where patients infected with different subtypes receive the same treatment.Methods
Clinical and demographic data were reported by physicians. Resistance was tested after treatment failure. Statistical analyses were conducted using SPSS.Results
607 LPV/r treated patients (365 male) were included. 139 had HIV subtype B, 391 C, and 77 other subtypes. At study end 429 (71%) were receiving LPV/r. No significant differences in PI treatment history and in median viral-load (VL) at treatment initiation and termination existed between subtypes. MSM discontinued LPV/r more often than others even when the virologic outcome was good (p = 0.001). VL was below detection level in 81% of patients for whom LPV/r was first PI and in 67% when it was second (P = 0.001). Median VL decrease from baseline was 1.9±0.1 logs and was not significantly associated with subtype. Median CD4 increase was: 162 and 92cells/µl, respectively, for patients receiving LPV/r as first and second PI (P = 0.001), and 175 and 98, respectively, for subtypes B and C (P<0.001). Only 52 (22%) of 237 patients genotyped while under LPV/r were fully resistant to the drug; 12(5%) were partially resistant. In48%, population sequencing did not reveal resistance to any drug notwithstanding the virologic failure. No difference was found in the rates of resistance development between B and C (p = 0.16).Conclusions
Treatment with LPV/r appeared efficient and tolerable in both subtypes, B and C, but CD4 recovery was significantly better in virologically suppressed subtype-B patients. In both subtypes, LPV/r was more beneficial when given as first PI. Mostly, reasons other than resistance development caused discontinuation of treatment. 相似文献74.
Ion Migration and the Role of Preconditioning Cycles in the Stabilization of the J–V Characteristics of Inverted Hybrid Perovskite Solar Cells 下载免费PDF全文
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M. T. Fernández-Espinar S. Vallés F. Piñaga J. A. Pérez-González D. Ramón 《Applied microbiology and biotechnology》1996,45(3):338-341
Using recombinant DNA techniques, an Aspergillus nidulans multicopy transformant for the gene xlnB coding for the minor X24 xylanase has been constructed. When grown on glucose as sole carbon source this transformant secretes 114 U of xylanase (mg
protein)-1. In this culture condition, X24 is the only xylanase secreted and the predominant protein in the culture filtrate. This strategy has been used to purify
the X24 enzyme to homogeneity. The purified xylanase showed a single band on sodium dodecyl sulphate/ polyacrylamide gel electrophoresis
with a molecular mass of 24 kDa and had an isoelectric point of approximately 3.5. The enzyme was a non-debranching endo-1,4-β-xylan
xylanohydrolase highly specific for xylans and showed optimal activity at pH 5.5 and 52°C. The X24 xylanase had a Michaelis constant, K
m, of 12.43 mg oat spelt xylan ml-1 and a V
max of 1639 μmol min-1 (mg protein)-1.
Received: 17 May 1995/Received last revision: 25 September 1995/Accepted: 29 September 1995 相似文献
78.
Exploitation of biological resources and the harvest of population species are commonly practiced in fisheries, forestry and
wild life management. Estimation of maximum harvesting effort has a great impact on the economics of fisheries and other bio-resources.
The present paper deals with the problem of a bioeconomic fishery model under environmental variability. A technique for finding
the maximum harvesting effort in fluctuating environment has been developed in a two-species competitive system, which shows
that under realistic environmental variability the maximum harvesting effort is less than what is estimated in the deterministic
model. This method also enables us to find out the safe regions in the parametric space for which the chance of extinction
of the species is minimized. A real life fishery problem has been considered to obtain the inaccessible parameters of the
system in a systematic way. Such studies may help resource managers to get an idea for controlling the system. 相似文献
79.
Spatial patterns of trees and juveniles in a laurel forest of Tenerife, Canary Islands 总被引:5,自引:0,他引:5
Spatial patterns are important characteristics of the forest and theycan reveal such things as successional status and ecological characteristics ofthe species. We tested the hypothesis that spatial distribution will bedifferent, depending on whether the species is intolerant or tolerant to shade.We assessed the spatial distribution of trees (> 4 cm dbh) andjuveniles in eight laurel forest plots. A univariate spatial analysis(performed with Ripley's K1) showed that all tree species havesignificantaggregation at short distances (2 m). Nevertheless, two groups ofspecies could be differentiated: Erica scoparia,Myrica faya and Ilex canariensisshowed a tendency for aggregation at large distances (larger than 6m)while L. azorica and Prunuslusitanicashowed aggregation only at shorter distances. Ripley's BivariateK1,2 analyses showed no significant differences in the spatialdistribution ofanalyzed species pairs from a null model. Only Laurusazoricahad a sufficient sample size for analysis of juvenile distribution. Aunivariateanalysis revealed thatL. azorica seedlings (stems < 50 cm high)were clumped in some plots up to 5 m, but this was not consistent.Saplings (stems > 50 cm high and < 4 cm dbh)didnot show strong clumping even at short distances. L.azoricasaplings had no significant aggregation with, nor repulsionfrom, adults of the same or different species. Spatial patterns of the speciesshould be considered in the development of restoration plans of the laurelforest 90%of which has disappeared or been intensively disturbed on Tenerife Island. 相似文献
80.
Billie‐Jean Martin Subodh Verma Francois Charbonneau Lawrence M. Title Eva M. Lonn Todd J. Anderson 《Obesity (Silver Spring, Md.)》2013,21(2):266-273