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Hasan A Yu J Smith DL Smith JB 《Protein science : a publication of the Protein Society》2004,13(2):332-341
The alpha-crystallins, alphaA and alphaB, are major lens structural proteins with chaperone-like activity and sequence homology to small heat-shock proteins. As yet, their crystal structures have not been determined because of the large size and heterogeneity of the assemblies they form in solution. Because alpha-crystallin chaperone activity increases with temperature, understanding structural changes of alpha-crystallin as it is heated may help elucidate the mechanism of chaperone activity. Although a variety of techniques have been used to probe changes in heat-stressed alpha-crystallin, the results have not yet yielded a clear understanding of chaperone activity. We report examination of native assemblies of human lens alpha-crystallin using hydrogen/deuterium exchange in conjunction with enzymatic digestion and analysis by mass spectrometry. This technique has the advantage of sensing structural changes along much of the protein backbone and being able to detect changes specific to alphaA and alphaB in the native assembly. The reactivity of the amide linkages to hydrogen/deuterium exchange was determined for 92% of the sequence of alphaA and 99% of alphaB. The behavior of alphaA and alphaB is remarkably similar. At low temperatures, there are regions at the beginning of the alpha-crystallin domains in both alphaA and alphaB that have high protection to isotope exchange, whereas the C termini offer little protection. The N terminus of alphaA also has low protection. With increasing temperatures, both proteins show gradual unfolding. The maximum percent change in exposure with increasing temperatures was found in alphaA 72-75 and alphaB 76-79, two regions considered critical for chaperone activity. 相似文献
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Pay-for-performance programs are often aimed to improve the management of chronic diseases. We evaluate the impact of a local pay for performance programme (QOF+), which rewarded financially more ambitious quality targets (‘stretch targets’) than those used nationally in the Quality and Outcomes Framework (QOF). We focus on targets for intermediate outcomes in patients with cardiovascular disease and diabetes. A difference-in-difference approach is used to compare practice level achievements before and after the introduction of the local pay for performance program. In addition, we analysed patient-level data on exception reporting and intermediate outcomes utilizing an interrupted time series analysis. The local pay for performance program led to significantly higher target achievements (hypertension: p-value <0.001, coronary heart disease: p-values <0.001, diabetes: p-values <0.061, stroke: p-values <0.003). However, the increase was driven by higher rates of exception reporting (hypertension: p-value <0.001, coronary heart disease: p-values <0.03, diabetes: p-values <0.05) in patients with all conditions except for stroke. Exception reporting allows practitioners to exclude patients from target calculations if certain criteria are met, e.g. informed dissent of the patient for treatment. There were no statistically significant improvements in mean blood pressure, cholesterol or HbA1c levels. Thus, achievement of higher payment thresholds in the local pay for performance scheme was mainly attributed to increased exception reporting by practices with no discernable improvements in overall clinical quality. Hence, active monitoring of exception reporting should be considered when setting more ambitious quality targets. More generally, the study suggests a trade-off between additional incentive for better care and monitoring costs. 相似文献
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The majority of soil microorganisms can derive ethylene from L-methionine (L-MET), while some rhizobacteria can hydrolyze 1-aminocyclopropane-1-carboxylate (ACC) due to their ACC-deaminase activity. In this study, three strains having either ACC-deaminase activity (Pseudomonas putida biotype A, A7), or the ability to produce ethylene from L-MET (Acinetobacter calcoaceticus, M9) or both (Pseudomonas fluorescens, AM3) were used for inoculation. The highly ethylene specific bioassay of a classical "triple" response in pea seedlings was used to investigate the effect of the inoculation with the rhizobacteria in the presence of 10 mM ACC or L-MET. The exogenous application of ACC had a concentration-dependent effect on the etiolated pea seedlings in creating the classical "triple" response. The inoculation with P. putida diluted the effect of ACC, which was most likely due to its ACC-deaminase activity. Similarly, the application of Co2+ reduced the ACC-imposed effect on etiolated pea seedlings. In contrast, the inoculation of A. calcoaceticus or P. fluorescens in the presence of L-MET caused a stronger classical "triple" response in etiolated pea seedlings; most likely by producing ethylene from L-MET. This is the first study, to our knowledge, reporting on the comparative effect of rhizobacteria capable of utilizing ACC vs L-MET on etiolated pea seedlings. 相似文献
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Extensive applications of persistent organochlorine pesticides like endosulfan on cotton have led to the contamination of
soil and water environments at several sites in Pakistan. Microbial degradation offers an effective approach to remove such
toxicants from the environment. This study reports the isolation of highly efficient endosulfan degrading bacterial strains
from soil. A total of 29 bacterial strains were isolated through enrichment technique from 15 specific sites using endosulfan
as sole sulfur source. The strains differed substantially in their potential to degrade endosulfan in vitro ranging from 40
to 93% of the spiked amount (100 mg l−1). During the initial 3 days of incubation, there was very little degradation but it got accelerated as the incubation period
proceeded. Biodegradation of endosulfan by these bacteria also resulted in substantial decrease in pH of the broth from 8.2
to 3.7 within 14 days of incubation. The utilization of endosulfan was accompanied by increased optical densities (OD595) of the broth ranging from 0.511 to 0.890. High performance liquid chromatography analyses revealed that endosulfan diol
and endosulfan ether were among the products of endosulfan metabolism by these bacterial strains while endosulfan sulfate,
a persistent and toxic metabolite of endosulfan, was not detected in any case. The presence of endosulfan diol and endosulfan
ether in the bacterial metabolites was further confirmed by GC-MS. Abiotic degradation contributed up to 21% of the spiked
amount. The three bacterial strains, Pseudomonas spinosa, P. aeruginosa, and Burkholderia cepacia, were the most efficient degraders of both α- and β-endosulfan as they consumed more than 90% of the spiked amount (100 mg l−1) in the broth within 14 days of incubation. Maximum biodegradation by these three selected efficient bacterial strains was
observed at an initial pH of 8.0 and at an incubation temperature of 30°C. The results of this study may imply that these
bacterial strains could be employed for bioremediation of endosulfan polluted soil and water environments. 相似文献
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The precise characterization of post translational modifications (PTMs) is important for the understanding of protein regulatory
mechanisms and their role in disease. However, experimental studies on PTMs, especially with multifunctional proteins are
difficult to follow and investigate. Bioinformatic tools are therefore helpful in predicting key protein modifications. To
study the role of PTMs in claudin proteins, specifically claudin-1, -3 and -4 in the onset or progression of human cancers,
we performed an in silico study of various PTMs and investigated their interplay. Given that the activity of claudins is known
to be influenced by two types of PTMs, specifically palmitoylation and kinase- dependent phosphorylation, we predicted two
conserved regions in the topological domains of claudin-1, -3 and -4 as potential palmitoylation sites. Furthermore, conserved
phosphorylation residues, which may be targets for kinases and can alter claudin’s ability to maintain the integrity of tight
junctions, were identified. To our knowledge, this is the first report to suggest O-glycosylation of claudin proteins, as well as a potential novel interplay between phosphorylation and O-glycosylation at Yin Yang sites. Thus, our findings may facilitate the production of anti-cancer drugs, and suggest that
novel therapeutic strategies should target post translational events. 相似文献