Structural analysis of Salmonella enterica effector protein SopD

Salmonella outer protein D (SopD) is a type III secreted virulence effector protein from Salmonella enterica. Full-length SopD and SopD lacking 16 amino acids at the N-terminus (SopDDeltaN) have been expressed as fusions with GST in Escherichia coli, purified with a typical yield of 20-30 mg per litre of cell culture and crystallized. Biophysical characterization has been carried out mainly on SopDDeltaN. Analytical size exclusion chromatography shows that SopDDeltaN is monomeric and probably globular in aqueous solution. The secondary structure composition, calculated from the CD spectrum, is mixed (38% alpha-helix and 26% beta-strand). Sequence analysis indicates that SopD contains a coiled coil motif, as found in numerous other type III secretion system-associated proteins. This suggests that SopD has the potential for one or more heterotypic protein-protein interactions. Limited trypsin digestion of SopDDeltaN, monitored by both one-dimensional proton NMR spectroscopy and SDS-PAGE, shows that the protein has a large, protease-resistant core domain of 286 amino acid residues. This single-domain architecture suggests that SopD lacks a cognate chaperone. In crystallization trials, SopDDeltaN produced better crystals than either full-length SopD or trypsin-digested SopDDeltaN. Diffraction to 3.0 Angstrom resolution has so far been obtained from crystals of SopDDeltaN

Analytic Representation of The Dirac Equation

In this paper we construct an analytical separation (diagonalization) of the full (minimal coupling) Dirac equation into particle and antiparticle components. The diagonalization is analytic in that it is achieved without transforming the wave functions, as is done by the Foldy-Wouthuysen method, and reveals the nonlocal time behavior of the particle-antiparticle relationship. We interpret the zitterbewegung and the result that a velocity measurement (of a Dirac particle) at any instant in time is, as reflections of the fact that the Dirac equation makes a spatially extended particle appear as a point in the present by forcing it to oscillate between the past and future at speed c. From this we infer that, although the form of the Dirac equation serves to make space and time appear on an equal footing mathematically, it is clear that they are still not on an equal footing from a physical point of view. On the other hand, the Foldy-Wouthuysen transformation, which connects the Dirac and square root operator, is unitary. Reflection on these results suggests that a more refined notion (than that of unitary equivalence) may be required for physical systems

Estimating the spectrum of a density matrix with LOCC

The problem of estimating the spectrum of a density matrix is considered. Other problems, such as bipartite pure state entanglement, can be reduced to spectrum estimation. A local operations and classical communication (LOCC) measurement strategy is shown which is asymptotically optimal. This means that, for a very large number of copies, it becomes unnecessary to perform collective measurements which should be more difficult to implement in practice.Comment: 12 pages, uses iopart.cls and iopart10.clo. Improved version. v3: Reference updated, added journal referenc

Generation of macroscopic quantum-superposition states by linear coupling to a bath

We demonstrate through an exactly solvable model that collective coupling to any thermal bath induces effectively nonlinear couplings in a quantum many-body (multi-spin) system. The resulting evolution can drive an uncorrelated large-spin system with high probability into a macroscopic quantum-superposition state. We discuss possible experimental realizations.Comment: 4 pages, 2 figures, Physical Review Letters (in press

Modeling personality structure using semantic relationships: Is the HEXACO Honesty-Humility a distinct trait?

Background: Although the Big Five model (BFM) of personality has been the dominant paradigm in personality research since the mid-1990s, it has recently been challenged by the HEXACO model, which contains an additional factor called Honesty-Humility. Since both these models of personality were developed using the same factor analytic techniques, there has been an ongoing but inconclusive debate about the relative merits of these competing models. Objective: This paper assesses the robustness of the Honesty-Humility trait using a technique based on the semantic relationships between personality trait adjectives. Design: Trait marker adjectives for the HEXACO Honesty-Humility and BFM Agreeableness and Neuroticism personality domains in the English language are translated into, and back-translated from, six Asian languages to generate lists of closely related trait terms known as schedonyms. The numbers of schedonyms found within and across the three personality domains are then compared, to determine whether the HEXACO Honesty-Humility factor is semantically distinct from the BFM traits of Agreeableness and Neuroticism. Results: Our fndings indicate that the Honesty-Humility trait domain is semantically distinct from the BFM traits of Agreeableness and Neuroticism, and therefore that there is at least one more personality trait beyond the BFM. The implications of these fndings, and the potential applications of this semantically-based technique for establishing the universal structure of the human personality, are briefy discussed. Conclusion: Our semantic analysis provides clear evidence that there is an Honesty-Humility trait domain in addition to the Agreeableness and Neuroticism traits, and therefore that HEXACO provides a better description of human personality than the BFM

Abnormalities of the p53 MDM2 and DCC genes in human leiomyosarcomas.

In this study we have screened a series of 29 primary leiomyosarcomas for abnormalities of both the p53 gene and the MDM2 gene, which encodes a p53-associated protein. SSCP (single-strand conformation polymorphism) analysis and direct sequencing of polymerase chain reaction (PCR)-amplified DNA were used to establish that 6/29 tumours possessed point mutations of the p53 gene. Using a monoclonal antibody that recognises the p53 protein in immunohistochemical staining experiments, we observed overexpression of the p53 protein in five of the six tumours containing point mutations in the p53 gene. Southern analysis of tumour DNA revealed that 2/29 tumours demonstrated amplification of the MDM2 gene. When considered together, these results indicate that alterations in both the p53 gene and MDM2 gene are important in the development of a significant minority of leiomyosarcomas. In addition, we have demonstrated a significant association between the presence of abnormalities of the p53 gene or MDM2 genes in leiomyosarcomas and a more advanced clinicopathological stage (P = 0.03). We have also examined the role of the DCC tumour-suppressor gene in the development of human soft-tissue tumours in a variety of histological types. Except for evidence of a rearrangement in a single leiomyosarcoma cell line, SK-UT-1, we have found no direct evidence to support a role for mutation of the gene in the development of human soft-tissue tumours

Dynamics of defect formation

A dynamic symmetry-breaking transition with noise and inertia is analyzed. Exact solution of the linearized equation that describes the critical region allows precise calculation (exponent and prefactor) of the number of defects produced as a function of the rate of increase of the critical parameter. The procedure is valid in both the overdamped and underdamped limits. In one space dimension, we perform quantitative comparison with numerical simulations of the nonlinear nonautonomous stochastic partial differential equation and report on signatures of underdamped dynamics.Comment: 4 pages, LaTeX, 4 figures. Submitted to Physical Revie

A study of the association between identity, life engagement and well-being among young Asian adults

The eudaemonic tradition asserts that life engagement, that is the pursuit of a meaningful way of living, is an important element of well-being. Self-identity theory posits that individuals’ identities significantly contribute to their sense of meaning and belonging, which in turn boost well-being. The present study aimed to establish the extent to which self-identities are predictors of wellbeing and whether they are subsumed within the life engagement construct. An opportunity sample of Singaporeans (n = 269) aged 18–35 (M = 23.88, SD = 4.52) completed the Aspects of Identity Questionnaire, Warwick-Edinburgh Mental Well-Being Scale and Life Engagement Test. Correlational analysis showed that personal, social, relational and collective identities were significantly associated with life engagement and well-being. However, multiple regressions demonstrated that life-engagement subsumed collective and relational identity almost completely, and also accounted for a significant amount of the variance in personal and social identities in the prediction of well-being, broadly supporting the eudaemonic model. It was shown that social and personal identities were predictors of well-being beyond life engagement, possibly because these identities satisfy some of psychological needs that promote various benefits that are independent of life engagement, yet still important for wellbeing. It is suggested that these differences in the salience of identity types to well-being may be indicative of changes in the sense of identity among young Singaporeans that have arisen as a result of social policy or possibly changes in the ways of identity expression in the Internet. The implications of the findings are discussed and recommendations made for future research