The transcriptional repressor protein NsrR senses nitric oxide directly via a [2Fe-2S] cluster

The regulatory protein NsrR, a member of the Rrf2 family of transcription repressors, is specifically dedicated to sensing nitric oxide (NO) in a variety of pathogenic and non-pathogenic bacteria. It has been proposed that NO directly modulates NsrR activity by interacting with a predicted [Fe-S] cluster in the NsrR protein, but no experimental evidence has been published to support this hypothesis. Here we report the purification of NsrR from the obligate aerobe Streptomyces coelicolor. We demonstrate using UV-visible, near UV CD and EPR spectroscopy that the protein contains an NO-sensitive [2Fe-2S] cluster when purified from E. coli. Upon exposure of NsrR to NO, the cluster is nitrosylated, which results in the loss of DNA binding activity as detected by bandshift assays. Removal of the [2Fe-2S] cluster to generate apo-NsrR also resulted in loss of DNA binding activity. This is the first demonstration that NsrR contains an NO-sensitive [2Fe-2S] cluster that is required for DNA binding activity

Study of cosolvent-induced α-chymotrypsin fibrillogenesis: Does protein surface hydrophobicity trigger early stages of aggregation reaction?

The misfolding of specific proteins is often associated with their assembly into fibrillar aggregates, commonly termed amyloid fibrils. Despite the many efforts expended to characterize amyloid formation in vitro, there is no deep knowledge about the environment (in which aggregation occurs) as well as mechanism of this type of protein aggregation. Alpha-chymotrypsin was recently driven toward amyloid aggregation by the addition of intermediate concentrations of trifluoroethanol. In the present study, approaches such as turbidimetric, thermodynamic, intrinsic fluorescence and quenching studies as well as chemical modification have been successfully used to elucidate the underlying role of hydrophobic interactions (involved in early stages of amyloid formation) in α-chymotrypsin-based experimental system. © 2009 Springer Science+Business Media, LLC

Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys

The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP ‘patch’ dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption

Restricted by borders: trade-offs in transboundary conservation planning for large river systems

Effective conservation of freshwater biodiversity requires accounting for connectivity and the propagation of threats along river networks. With this in mind, the selection of areas to conserve freshwater biodiversity is challenging when rivers cross multiple jurisdictional boundaries. We used systematic conservation planning to identify priority conservation areas for freshwater fish conservation in Hungary (Central Europe). We evaluated the importance of transboundary rivers to achieve conservation goals by systematically deleting some rivers from the prioritization procedure in Marxan and assessing the trade-offs between complexity of conservation recommendations (e.g., conservation areas located exclusively within Hungary vs. transboundary) and cost (area required). We found that including the segments of the largest transboundary rivers (i.e. Danube, Tisza) in the area selection procedure yielded smaller total area compared with the scenarios which considered only smaller national and transboundary rivers. However, analyses which did not consider these large river segments still showed that fish diversity in Hungary can be effectively protected within the country’s borders in a relatively small total area (less than 20 % of the country’s size). Since the protection of large river segments is an unfeasible task, we suggest that transboundary cooperation should focus on the protection of highland riverine habitats (especially Dráva and Ipoly Rivers) and their valuable fish fauna, in addition to the protection of smaller national rivers and streams. Our approach highlights the necessity of examining different options for selecting priority areas for conservation in countries where transboundary river systems form the major part of water resources.Full Tex

Imaging Chromophores With Undetectable Fluorescence by Stimulated Emission Microscopy

Fluorescence, that is, spontaneous emission, is generally more sensitive than absorption measurement, and is widely used in optical imaging. However, many chromophores, such as haemoglobin and cytochromes, absorb but have undetectable fluorescence because the spontaneous emission is dominated by their fast non-radiative decay. Yet the detection of their absorption is difficult under a microscope. Here we use stimulated emission, which competes effectively with the nonradiative decay, to make the chromophores detectable, and report a new contrast mechanism for optical microscopy. In a pump-probe experiment, on photoexcitation by a pump pulse, the sample is stimulated down to the ground state by a time-delayed probe pulse, the intensity of which is concurrently increased. We extract the miniscule intensity increase with shot-noise-limited sensitivity by using a lock-in amplifier and intensity modulation of the pump beam at a high megahertz frequency. The signal is generated only at the laser foci owing to the nonlinear dependence on the input intensities, providing intrinsic three-dimensional optical sectioning capability. In contrast, conventional one-beam absorption measurement exhibits low sensitivity, lack of three-dimensional sectioning capability, and complication by linear scattering of heterogeneous samples. We demonstrate a variety of applications of stimulated emission microscopy, such as visualizing chromoproteins, non-fluorescent variants of the green fluorescent protein, monitoring lacZ gene expression with a chromogenic reporter, mapping transdermal drug distributions without histological sectioning, and label-free microvascular imaging based on endogenous contrast of haemoglobin. For all these applications, sensitivity is orders of magnitude higher than for spontaneous emission or absorption contrast, permitting nonfluorescent reporters for molecular imaging.Chemistry and Chemical Biolog

Evidence for Genetic Overlap Between Schizophrenia and Age at First Birth in Women

IMPORTANCE: A recently published study of national data by McGrath et al in 2014 showed increased risk of schizophrenia (SCZ) in offspring associated with both early and delayed parental age, consistent with a U-shaped relationship. However, it remains unclear if the risk to the child is due to psychosocial factors associated with parental age or if those at higher risk for SCZ tend to have children at an earlier or later age. OBJECTIVE: To determine if there is a genetic association between SCZ and age at first birth (AFB) using genetically informative but independently ascertained data sets. DESIGN, SETTING, AND PARTICIPANTS: This investigation used multiple independent genome-wide association study data sets. The SCZ sample comprised 18 957 SCZ cases and 22 673 controls in a genome-wide association study from the second phase of the Psychiatric Genomics Consortium, and the AFB sample comprised 12 247 genotyped women measured for AFB from the following 4 community cohorts: Estonia (Estonian Genome Center Biobank, University of Tartu), the Netherlands (LifeLines Cohort Study), Sweden (Swedish Twin Registry), and the United Kingdom (TwinsUK). Schizophrenia genetic risk for each woman in the AFB community sample was estimated using genetic effects inferred from the SCZ genome-wide association study. MAIN OUTCOMES AND MEASURES: We tested if SCZ genetic risk was a significant predictor of response variables based on published polynomial functions that described the relationship between maternal age and SCZ risk in offspring in Denmark. We substituted AFB for maternal age in these functions, one of which was corrected for the age of the father, and found that the fit was superior for the model without adjustment for the father's age. RESULTS: We observed a U-shaped relationship between SCZ risk and AFB in the community cohorts, consistent with the previously reported relationship between SCZ risk in offspring and maternal age when not adjusted for the age of the father. We confirmed that SCZ risk profile scores significantly predicted the response variables (coefficient of determination R2 = 1.1E-03, P = 4.1E-04), reflecting the published relationship between maternal age and SCZ risk in offspring by McGrath et al in 2014. CONCLUSIONS AND RELEVANCE: This study provides evidence for a significant overlap between genetic factors associated with risk of SCZ and genetic factors associated with AFB. It has been reported that SCZ risk associated with increased maternal age is explained by the age of the father and that de novo mutations that occur more frequently in the germline of older men are the underlying causal mechanism. This explanation may need to be revised if, as suggested herein and if replicated in future studies, there is also increased genetic risk of SCZ in older mothers

Wild chimpanzees modify modality of gestures according to the strength of social bonds and personal network size

Primates form strong and enduring social bonds with others and these bonds have important fitness consequences. However, how different types of communication are associated with different types of social bonds is poorly understood. Wild chimpanzees have a large repertoire of gestures, from visual gestures to tactile and auditory gestures. We used social network analysis to examine the association between proximity bonds (time spent in close proximity) and rates of gestural communication in pairs of chimpanzees when the intended recipient was within 10 m of the signaller. Pairs of chimpanzees with strong proximity bonds had higher rates of visual gestures, but lower rates of auditory long-range and tactile gestures. However, individual chimpanzees that had a larger number of proximity bonds had higher rates of auditory and tactile gestures and lower rates of visual gestures. These results suggest that visual gestures may be an efficient way to communicate with a small number of regular interaction partners, but that tactile and auditory gestures may be more effective at communicating with larger numbers of weaker bonds. Increasing flexibility of communication may have played an important role in managing differentiated social relationships in groups of increasing size and complexity in both primate and human evolution

Hydrodynamic properties of cyclodextrin molecules in dilute solutions

Three well-known representatives of the cyclodextrin family were completely characterized by molecular hydrodynamics methods in three different solvents. For the first time the possibility of an estimation of velocity sedimentation coefficients s between 0.15 and 0.5 S by the numerical solution of the Lamm equation is shown. Comparison of the experimental hydrodynamic characteristics of the cyclodextrins with theoretical calculations for toroidal molecules allows an estimation of the thickness of the solvent layers on the surface of cyclodextrin molecules

Ribosome formation from subunits studied by stopped-flow and Rayleigh light scattering

Light scattering and standard stopped-flow techniques were used to monitor rapid association of ribosomal subunits during initiation of eubacterial protein synthesis. The effects of the initiation factors IF1, IF2, IF3 and buffer conditions on subunit association were studied along with the role of GTP in this process. The part of light scattering theory that is essential for kinetic measurements is high-lighted in the main text and a more general treatment of Rayleigh scattering from macromolecules is given in an appendix