A mixed disulfide bond in bacterial glutathione transferase: functional and evolutionary implications

BACKGROUND: Glutathione S-transferases (GSTs) are a multifunctional group of enzymes, widely distributed in aerobic organisms, that have a critical role in the cellular detoxification process. Unlike their mammalian counterparts, bacterial GSTs often catalyze quite specific reactions, suggesting that their roles in bacteria might be different. The GST from Proteus mirabilis (PmGST B1-1) is known to bind certain antibiotics tightly and reduce the antimicrobial activity of beta-lactam drugs. Hence, bacterial GSTs may play a part in bacterial resistance towards antibiotics and are the subject of intense interest. RESULTS: Here we present the structure of a bacterial GST, PmGST B1-1, which has been determined from two different crystal forms. The enzyme adopts the canonical GST fold although it shares less than 20% sequence identity with GSTs from higher organisms. The most surprising aspect of the structure is the observation that the substrate, glutathione, is covalently bound to Cys 10 of the enzyme. In addition, the highly structurally conserved N-terminal domain is found to have an additional beta strand. CONCLUSIONS: The crystal structure of PmGST B1-1 has highlighted the importance of a cysteine residue in the catalytic cycle. Sequence analyses suggest that a number of other GSTs share this property, leading us to propose a new class of GSTs - the beta class. The data suggest that the in vivo role of the beta class GSTs could be as metabolic or redox enzymes rather than conjugating enzymes. Compelling evidence is presented that the theta class of GSTs evolved from an ancestral member of the thioredoxin superfamily.     

Low-frequency characteristics of thin-film multijunction thermalvoltage converters

Low-frequency errors of thin-film multijunction thermal voltage converters are estimated using a simple model based on easily measured parameters. The model predictions are verified by measuring the converter's frequency characteristic using a digitally synthesized source     

The effect of stimulus range on perceived contrast: Evidence for contrast gain control.

Investigated whether the stimulus range affected the perceived contrast of vertical gratings whose spatial frequencies were either 1 or 4 cycles/deg to determine if adjustive processes apply to the contrast sensitivity of spatial frequency channels in a vision task. Nine Ss judged the perceived contrasts of 1 and 4 cycle/deg gratings intermixed within a session. Four different conditions were created by combining either a set of low-contrast or high-contrast gratings at 1 frequency with a broad range of contrasts at the other frequency. When the broad-range set was at 1 cycle/deg, contrast-matches across spatial frequencies were unaffected by changing the range of the 4-cycle/deg gratings. When the broad-range set was 4 cycles/deg, contrast matches were changed by changing the range of the 1 cycle/deg gratings. This asymmetry in the range effect was shown to be consistent with the characteristics of the 2 channels' receptive-field profiles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Customer satisfaction and self-reported treatment outcomes among psychiatric inpatients

OBJECTIVE: Relationships among different dimensions of patient satisfaction and selected demographic, clinical, and outcome variables were explored in a sample of severely ill people receiving inpatient psychiatric services. METHOD: The sample consisted of 81 patients admitted to and discharged from an inpatient psychiatric unit at a midwestern Veterans Affairs medical center. Stepwise multiple regression was used to examine the relationship between patient satisfaction and self-reported changes in quality of life, symptomatology, and level of functioning as measured by the Treatment Outcome Profile. Other variables such as diagnosis, length of stay, employment, living situation, and prior psychiatric and substance abuse treatment were also considered. A subsample of the most satisfied and dissatisfied patients was chosen to further explore variables contributing to satisfaction with services. RESULTS: Patient satisfaction was related to initial level of functioning, certain diagnoses, and treatment gains. Clinicians were highly accurate in identifying patients who were satisfied, based on blind chart reviews. CONCLUSIONS: This study underscores the significant relationships between patient satisfaction, psychiatric diagnosis, and other outcome measures, and argues for the validity and utility of patient satisfaction measures in assessing the efficacy of inpatient care.     

An on-line microcomputing system for the acquisition and processing of data from a fourier spectrometer

A microcomputing system has been developed to provide on-line data acquisition and analysis for a Fourier transform spectrometer, and the interface between the spectrometer and the microcomputer is described in detail. The system has been equipped with software which includes a fast Fourier transform programme for use in either conventional or dispersive Fourier transform spectroscopy, and programmes for calculating the optical constants and dielectric functions of solids from complex spectra obtained by dispersive Fourier transform spectroscopy.     

Approximation programming of chemical processes—2: computational difficulties

Part 1 of this series presents successful results in implementing quadratic approximation programming for optimization of processes modelled with Monsanto's FLOWTRAN®³ system. Detailed analysis of the computations indicates that the optimization of the approximate quadratic models provides one of the main computational problems. This paper describes some of these problems and our solutions, and indicates further improvements which should be investigated.     

Effect of pulpmill effluent on dissolved oxygen in a stratified estuary—I. Empirical observations

Pulpmill effluent discharged at the surface in Alberni Inlet is shown to prevent oxygen production in the stratum immediately beneath the halocline by restricting light penetration. This stratum is the source of marine water for entrainment in the halocline and to the upper mixed zone. This situation cannot be remedied by removal of BOD from the pulpmill effluent, rather the staining properties must be diminished or removed.