Dimer-dimer stacking interactions are important for nucleic acid binding by the archaeal chromatin protein Alba

Archaea use a variety of small basic proteins to package their DNA. One of the most widespread and highly conserved is the Alba (Sso10b) protein. Alba interacts with both DNA and RNA in vitro, and we show in the present study that it binds more tightly to dsDNA (double-stranded DNA) than to either ssDNA (single-stranded DNA) or RNA. The Alba protein is dimeric in solution, and forms distinct ordered complexes with DNA that have been visualized by electron microscopy studies; these studies suggest that, on binding dsDNA, the protein forms extended helical protein fibres. An end-to-end association of consecutive Alba dimers is suggested by the presence of a dimer-dimer interface in crystal structures of Alba from several species, and by the strong conservation of the interface residues, centred on Are and Phe(60). In the present study we map perturbation of the polypeptide backbone of Alba upon binding to DNA and RNA by NMR, and demonstrate the central role of Phe(60) in forming the dimer dimer interface. Site-directed spin labelling and pulsed ESR are used to confirm that an end-to-end, dimer dimer interaction forms in the presence of dsDNA.Publisher PDFPeer reviewe

Energetic problems faced by micro-organisms growing or surviving on parsimonious energy sources and at acidic pH: I. Acidithiobacillus ferrooxidans as a paradigm

AbstractThe mitochondrial paradigm for a chemiosmotic energy transduction mechanism requires frequently misunderstood modifications for application to microbes growing and surviving at acidic pH values and/or with relatively weak reductants as energy sources. Here the bioenergetics of the iron oxidiser Acidithiobacillus ferrooxidans are reviewed and analysed so as to develop the general bioenergetic principles for understanding organisms that grow under these conditions. Extension of the principles outlined herein to organisms that survive (as opposed to grow) under these conditions is to be presented in a subsequent article

Elucidating the Roles of Motives and Gains in Exercise Participation

Previous research into the role of exercise motives (what people want from exercise) has overlooked the possible role of gains (what people get) and hence the possible benefits of motive fulfillment (when people get what they want). To redress this imbalance, we examined the additive and interactive effects of motives and subjective gains on exercise-specific outcomes. Young adults (N = 196) completed measures of exercise motives and gains, and exercise behavioral regulation, amount, satisfaction, and intention. Four representative motives/gains were selected: appearance, positive health, challenge, and affiliation. Path analysis was used to test the effects of motives, gains, and their products (the interactive effects) on behavioral regulations, and thereby exercise amount, satisfaction, and intention. Controlled regulation increased with appearance motive, unless appearance gain was high. Controlled regulation had a negative effect on exercise satisfaction. Autonomous regulation increased with positive health motive, provided positive health gain was high; with challenge motive and gain; and with affiliation motive. Autonomous regulation had positive effects on exercise amount, satisfaction, and intention. The study corroborates previous findings about the effects of motives. It establishes the value of also studying gains, as moderators of the effects of motives, and in their own right. The findings are interpretable in terms of self-determination theory. Exercise promotion could be more effective if it focused on gains in conjunction with motives

Attribution in sport psychology: Seeking congruence between theory, research and practice

Objectives: This paper urges revision of the way attributions are conceptualised, investigated, and applied in sport psychology. There has been a recent decline in attribution research in sport psychology, despite the generally accepted relevance of attributions in applied settings. In seeking closer links between attribution theory, research, and practice, we argue that there is a mismatch between research and practice in sport psychology. Methods: Relevant literature is reviewed and theoretical arguments offered within seven sub-headings: Attribution theory in practice; linking consistency, distinctiveness, and consensus information to attribution dimensions; controllability as the primary attribution dimension; the generalisability of controllability; assessing attributions; implications for practice; and the social context. Results and conclusions: Research within sport psychology should focus on the central issue of how controllability attributions generalise across time, situations, and people. Measurement should reflect this approach to research within the field of attributions and, to this end, researchers might consider using a variety of quantitative and qualitative methods of inquiry. Practitioners should use consistency, distinctiveness, and consensus information to challenge clients' attributional thinking and help them attain adaptive perceptions of controllability. Practitioners should also help clients to be their own psychologist. Future research and practice should include a consideration of the social context in which attributions are shaped. © 2004 Elsevier Ltd. All rights reserved

Performance assessment in sport: Formulation, justification, and confirmatory factor analysis of a measurement instrument for tennis performance

publication-status: Publishedtypes: ArticleCopyright © 2000 Taylor & Francis. This is an Author's Accepted Manuscript of an article published in Journal of Applied Sport Psychology available online at: http://www.tandfonline.com/doi/abs/10.1080/10413200008404223#.VNnjyp1FDcsThe present study reports the refinement and confirmatory factor analysis of a performance assessment instrument designed for tennis, first reported in Pees, Ingledew, and Hardy (1999). Background and justification for this study are reported, together with a detailed description of the sequential model-testing approach (Joreskog, 1993) adopted. The factor structure of the instrument was tested using a sample of 155 full-time tennis players. Analyses revealed good fit for the proposed model to the new data sample, and provided confirmation for the seven performance factors: Execution of (Flexible) Plan, Loss of Composure, Feeling Flat, Determination, Worry, Flow, and Effective Tactics. Performance factors discriminated between winners and losers. Performers should look at the various factors comprising overall performance; in a sense, the processes by which they come to achieve their successes

Social support dimensions and components of performance in tennis.

types: Comparative Study; Journal ArticleCopyright © 1999 Taylor & Francis. This is an Author's Accepted Manuscript of an article published in Journal of Sports Sciences, 1999 Vol. 17, Issue 5, pp. 421 – 429 available online at: http://www.tandfonline.com/doi/abs/10.1080/026404199365948The aim of this study was to explore the relationships between dimensions of social support and components of performance in tennis. A post-match performance measure was completed by 144 British tournament tennis players. Principal components analysis yielded eight components, labelled Execution of (Flexible) Plan, Loss of Composure, Feeling Flat, Positive Tension, Worry, Flow, Effective Tactics and Double Faults. Before the match, 46 players had also completed the Interpersonal Support Evaluation List. Stepwise regression analyses revealed significant effects of the Belonging and Appraisal dimensions of the Interpersonal Support Evaluation List on five of the performance components. The correlations between total support and four of these performance components were also significant. Logistic regression analyses revealed no significant effects of the dimensions of the Interpersonal Support Evaluation List or Total Support upon winning versus losing. Effects of social support upon performance were therefore only apparent when attention was focused on the components of performance

Characterisation of a near infra-red absorption band of the Escherichia coli quinol oxidase, cytochrome o, which is attributable to the high-spin ferrous haem of the binuclear site

AbstractThe bacterial quinol oxidase, cytochrome o, is an enzyme which is highly analogous to the better known cytochrome c oxidase, cytochrome aa3 but with the important difference that it lacks the near infra-red absorbing pigment CuA. In this article we report an absorption band in the near IR spectrum of cytochrome o with a maximal absorption at 738 nm, and which is attributable to the ferrous high-spin haem. The 758 nm band has an extinction coefficient or 0.2–0.3 mM−1·cm−1 at 758–800 nm. This region in cytochrome aa3, is dominated by the CuA absorption. The 758 nm absorption is lost on addition of CO or cyanide to the reduced enzyme. The carbon monoxide compound of cytochrome o also has absorbance bands in the near infra-red, and these may be attributable to a low-spin ferrous haem compound