Structural and functional analysis of two universal stress proteins YdaA and YnaF from Salmonella typhimurium: possible roles in microbial stress tolerance

In many organisms ``Universal Stress Proteins'' CUSPS) are induced in response to a variety of environmental stresses. Here we report the structures of two USPs, YnaF and YdaA from Salmonella typhimurium determined at 1.8 angstrom and 2.4 angstrom resolutions, respectively. YnaF consists of a single USP domain and forms a tetrameric organization stabilized by interactions mediated through chloride ions. YdaA is a larger protein consisting of two tandem USP domains. Two protomers of YdaA associate to form a structure similar to the YnaF tetramer. YdaA showed ATPase activity and an ATP binding motif G-2X-G-9X-G(S/T/N) was found in its C-terminal domain. The residues corresponding to this motif were not conserved in YnaF although YnaF could bind ATP. However, unlike YdaA, YnaF did not hydrolyse ATP in vitro. Disruption of interactions mediated through chloride ions by selected mutations converted YnaF into an ATPase. Residues that might be important for ATP hydrolysis could be identified by comparing the active sites of native and mutant structures. Only the C-terminal domain of YdaA appears to be involved in ATP hydrolysis. The structurally similar N-terminal domain was found to bind a zinc ion near the segment equivalent to the phosphate binding loop of the C-terminal domain. Mass spectrometric analysis showed that YdaA might bind a ligand of approximate molecular weight 800 daltons. Structural comparisons suggest that the ligand, probably related to an intermediate in lipid A biosynthesis, might bind at a site close to the zinc ion. Therefore, the N-terminal domain of YdaA binds zinc and might play a role in lipid metabolism. Thus, USPs appear to perform several distinct functions such as ATP hydrolysis, altering membrane properties and chloride sensing. (C) 2015 Elsevier Inc. All rights reserved.

Gamma oscillations in the midbrain spatial attention network: linking circuits to function

Gamma-band (25-140 Hz) oscillations are ubiquitous in mammalian forebrain structures involved in sensory processing, attention, learning and memory. The optic tectum (01) is the central structure in a midbrain network that participates critically in controlling spatial attention. In this review, we summarize recent advances in characterizing a neural circuit in this midbrain network that generates large amplitude, space-specific, gamma oscillations in the avian OT, both in vivo and in vitro. We describe key physiological and pharmacological mechanisms that produce and regulate the structure of these oscillations. The extensive similarities between midbrain gamma oscillations in birds and those in the neocortex and hippocampus of mammals, offer important insights into the functional significance of a midbrain gamma oscillatory code.

System reliability of randomly vibrating structures: Computational modeling and laboratory testing

The problem of determination of system reliability of randomly vibrating structures arises in many application areas of engineering. We discuss in this paper approaches based on Monte Carlo simulations and laboratory testing to tackle problems of time variant system reliability estimation. The strategy we adopt is based on the application of Girsanov's transformation to the governing stochastic differential equations which enables estimation of probability of failure with significantly reduced number of samples than what is needed in a direct simulation study. Notably, we show that the ideas from Girsanov's transformation based Monte Carlo simulations can be extended to conduct laboratory testing to assess system reliability of engineering structures with reduced number of samples and hence with reduced testing times. Illustrative examples include computational studies on a 10 degree of freedom nonlinear system model and laboratory/computational investigations on road load response of an automotive system tested on a four post Lest rig. (C) 2015 Elsevier Ltd. All rights reserved.

Analysis of five glucometers available in India

In this study, we report on the accuracy, precision and clinical acceptability of the five blood glucose meters available in India. Glucose levels of 100 blood samples were measured with each meter, at IISc health centre laboratory under same conditions and the results were compared with laboratory reference standard. In order to calculate the coefficient of variation (CV), each sample was tested three times. None of the glucometer showed 100 % compliance on CV measure. In terms of accuracy, none of the glucometer satisfied the most stringent ADA-1994 standard. In general all the glucometers showed improved accuracy with respect to the most relaxed ISO 1597:2003 standard. The Clarke error grid analysis was performed to assess the clinical acceptability of the glucometers. All five glucometers had more than 90 % of test results in Zone A and B. Bland-Altman analysis indicates that all glucometers show a positive bias, indicating that the measured values tend to be higher than the laboratory reference standard.