Accelerated X-ray Structure Elucidation of a 36 kDa Muramidase/Transglycosylase Using wARP

The X-ray structure of the 36kDa soluble lytic transglycosylase from Escherichia coli has been determined starting with the multiple isomorphous replacement method with inclusion of anomalous scattering at 2.7 Å resolution. Subsequently, before any model building was carried out, phases were extended to 1.7 Å, resolution with the weighted automated refinement procedure wARP, which gave a dramatic improvement in the phases. The electron-density maps from wARP were of outstanding quality for both the main chain and the side chains of the protein, which allowed the time spent on the tracing, interpretation and building of the X-ray structure to be substantially shortened. The structure of the soluble lyric transglycosylase was refined at 1.7 Å, resolution with X-PLOR to a final crystallographic R factor of 18.9%. Analysis of the wARP procedure revealed that the use of the maximum-likelihood refinement in wARP gave much better phases than least-squares refinement, provided that the ratio of reflections to protein atom parameters was approximately 1.8 or higher. Furthermore, setting aside 5% of the data for an Rfree test set had a negative effect on the phase improvement. The mean WwARP, a weight determined at the end of the wARP procedure and based on the variance of structure factors from six individually refined wARP models, proved to be a better indicator than the Rfree factor to judge different phase improvement protocols. The elongated Slt35 structure has three domains named the alpha, beta and core domains. The alpha domain contains mainly α-helices, while the beta domain consists of a five-stranded antiparallel β-sheet flanked by a short α-helix. Sandwiched between the alpha and beta domains is the core domain, which bears some resemblance to the fold of the catalytic domain of the previously elucidated 70 kDa soluble lytic transglycosylase from E. coli. The putative active site is at the bottom of a large deep groove in the core domain.

Controversen in de tandheelkunde:voorwoord

Het onlangs gehouden jubileumcongres ter gelegenheid van het honderdjarig bestaan van de Nederlandse Vereniging van Tandartsen had als thema Controversen in de tandheelkunde. Hierbij stond de vraag centraal of er nog, en zo ja welke, controversen bestaan in de restauratieve tandheelkunde. Bij de opzet van het congres werd gekozen voor een aantal onderwerpen waarmee de tandarts-algemeen practicus bijna dagelijks wordt geconfronteerd

Standards of diabetic care successes and failures of a patient education policy

Objective. To determine: (i) some aspects of the quality of medical care provided for adult diabetic patients in primary care settings; and (ii) changes in these variables 1 year after attending a specialist diabetes clinic that provided 2 - 3 hours of self-care education. Design. An analysis of the prevalences of obesity, uncontrolled diabetes, hypertension and hypercholesterolaemia at entry and 1 year later.Setting. Diabetes Clinic, Johannesburg Hospital, South Africa.Patients. Ninety randomly selected adult diabetic patients (46 black), with duration of diabetes ≥1 year at the first assessment.Results. At entry insulin-treated (N = 46) and non-insulintreated (N = 44) subjects showed prevalences of obesity (body mass index > 30) of 17% and 36%, respectively; there was unsatisfactory glycaemic control (haemoglobin A1C ≥ 9.5%) in 72% and 64%; untreated hypertension (blood pressure > 160/90 mmHg) in 24% and 23%; and untreated hypercholesterolaemia (> 7.0 mmol/l) in 15% and 11%. One year later weight had increased only in the non-insulintreated patients (+ 1.9 kg, P < 0.01). Mean HbA1C had improved (P < 0.D1 in both groups), but remained unsatisfactory in 49% of patients. Blood pressure control was poor in 14 of the 22 hypertensive patients; and hypercholesterolaemia persisted in 11 subjects. At presentation the patterns of poor control were similar in black and white patients, and the rates of improvement were comparable.Conclusion. There was a low rate of overall metabolic control of diabetes and its associations in primary care settings, with only limited improvements as a result of attending a dedicated diabetes clinic

Crystal structure of a murine α-class glutathione S-transferase involved in cellular defense against oxidative stress

Glutathione S-transferases (GSTs) are ubiquitous multifunctional enzymes which play a key role in cellular detoxification. The enzymes protect the cells against toxicants by conjugating them to glutathione. Recently, a novel subgroup of α-class GSTs has been identified with altered substrate specificity which is particularly important for cellular defense against oxidative stress. Here, we report the crystal structure of murine GSTA4-4, which is the first structure of a prototypical member of this subgroup. The structure was solved by molecular replacement and refined to 2.9 Å resolution. It resembles the structure of other members of the GST superfamily, but reveals a distinct substrate binding site.

Uncertainties of predictions from parton distribution functions II: the Hessian method

We develop a general method to quantify the uncertainties of parton distribution functions and their physical predictions, with emphasis on incorporating all relevant experimental constraints. The method uses the Hessian formalism to study an effective chi-squared function that quantifies the fit between theory and experiment. Key ingredients are a recently developed iterative procedure to calculate the Hessian matrix in the difficult global analysis environment, and the use of parameters defined as components along appropriately normalized eigenvectors. The result is a set of 2d Eigenvector Basis parton distributions (where d=16 is the number of parton parameters) from which the uncertainty on any physical quantity due to the uncertainty in parton distributions can be calculated. We illustrate the method by applying it to calculate uncertainties of gluon and quark distribution functions, W boson rapidity distributions, and the correlation between W and Z production cross sections.Comment: 30 pages, Latex. Reference added. Normalization of Hessian matrix changed to HEP standar