Conformational effects on the pro-S hydrogen abstraction reaction in cyclooxygenase-1: an integrated QM/MM and MD study

A key step in the cyclooxygenase reaction cycle of cyclooxygenase 1 (COX-1) is abstraction of the pro-S hydrogen atom of the arachidonic acid by a radical that is formed at the protein residue Tyr-385. Here we investigate this reaction step by a quantum-mechanics/molecular-mechanics approach in combination with molecular-dynamics simulations. The simulations identify the hydrogen abstraction angle as a crucial geometric determinant of the reaction, thus revealing the importance of the cyclooxygenase active site for calculating the potential energy surface of the reaction

Standard SANC modules for NLO QCD Radiative Corrections to Single-top Production

It this paper we present the results obtained with the newly created Standard SANC modules for calculation of the NLO QCD corrections to single top production processes in s and t channels at the partonic level, as well as top-decays. The main aim of these results is to prove the correct work of modules. A comprehensive comparison with results of the CompHEP system is given, where possible. These modules are intended to be used in Monte Carlo generators for single top production processes at the LHC. As in our recent paper, devoted to the electroweak corrections to these processes, we study the regularization of the top-legs associated infrared divergences with aid of the complex mass of the top quark. A comparison of QCD corrections with those computed by the conventional method is presented both for top production and decays. For s channel production we give an analytic proof of equivalence of the two methods in the limit of low top width.Comment: 21 pages, 2 figures, 17 table

Refining the predictions of supersymmetric CP-violating models: A top-down approach

We explore in detail the consequences of the CP-violating phases residing in the supersymmetric and soft SUSY breaking parameters in the approximation that family flavour mixings are ignored. We allow for non-universal boundary conditions and in such a consideration the model is described by twelve independent CP-violating phases and one angle which misaligns the vacuum expectation values (VEVs) of the Higgs scalars. We run two-loop renormalization group equations (RGEs), for all parameters involved, including phases, and we properly treat the minimization conditions using the one-loop effective potential with CP-violating phases included. We show that the two-loop running of phases may induce sizable effects for the electric dipole moments (EDMs) that are absent in the one-loop RGE analysis. Also important corrections to the EDMs are induced by the Higgs VEVs misalignment angle which are sizable in the large tanb region. Scanning the available parameter space we seek regions compatible with accelerator and cosmological data with emphasis on rapid neutralino annihilations through a Higgs resonance. It is shown that large CP-violating phases, as required in Baryogenesis scenarios, can be tuned to obtain agreement with WMAP3 cold dark matter constraints, EDMs and all available accelerator data, in extended regions of the parameter space which may be accessible to LHC.Comment: 41 pages, 22 eps figures. A reference added and a typo corrected; version to appear in JHE

CP Violation In Single Top Production And Decay Via p p-bar -> t b-bar +X -> W^+ b b-bar +X Within The MSSM: A Possible Application For Measuring \arg(A_t) At Hadron Colliders

CP-nonconserving effects in the reaction p p-bar -> t b-bar +X -> W^+ b b-bar +X, driven by the supersymmetric CP-odd phase of the stop trilinear soft breaking term, \arg(A_t), are studied. We discuss the CP-nonconserving effects in both production and the associated decay amplitudes of the top. We find that, within a plausible low energy scenario of the MSSM and keeping the neutron electric dipole moment below its current limit, a CP-violating cross-section asymmetry as large as 2-3% can arise if some of the parameters lie in a favorable range. A partial rate asymmetry originating only in the top decay t -> W^+ b is found to be, in general, below the 0.1% level which is somewhat smaller than previous claims. For a low \tan\beta of order one the decay asymmetry can reach at the most ~0.3%. This (few) percent level overall CP-violating signal in p p-bar -> t b-bar +X -> W^+ b b-bar +X might be within the reach of the future 2(4) TeV pp-bar Tevatron collider that may be able to produce ~10000(~30000) such tb-bar events with an integrated luminosity of 30 fb^{-1}. In particular, it may be used to place an upper bound on \arg(A_t) if indeed \arg(\mu) -> 0, as implied from the present experimental limit on the neutron electric dipole moment. The partial rate asymmetry in the top decay (~few \times 10^{-3}) may also be within the reach of the LHC with ~10^7 pairs of tt-bar produced, provided detector systematics are sufficiently small. We also show that if the GUT-scale universality of the soft breaking trilinear $A$ terms is relaxed, then the phases associated with \arg A_u and \arg A_d can take values up to ~few \times 10^{-1} even with squarks and gluino masses of several hundred GeV's without contradicting the experimental limit on the neutron electric dipole moment.Comment: 39 pages, plain latex, 20 figures embadded in the text using epsfi

CP Nonconservation in ppˉ→tbˉXp\bar p\to t\bar b X at the Tevatron

The reaction $p\bar p\to t\bar bX$ is found to be rather rich in exhibiting several different types of CP asymmetries. The spin of the top quark plays an important role. Asymmetries are related to form factors arising from radiative corrections of the $tbW$ production vertex due to non-standard physics. As illustrations, effects are studied in two Higgs Doublet Models and in Supersymmetric Models; asymmetries up to a few percent may be possible.Comment: 14 pages, 3 figures. Note: replaced due to minor problems that appeared on some postscript previewers. No change in conten

QCD corrections to decay-lepton polar and azimuthal angular distributions in e+e- -> t tbar in the soft-gluon approximation

QCD corrections to order alpha_s in the soft-gluon approximation to angular distributions of decay charged leptons in the process e+e- -> t tbar followed by semileptonic decay of t or tbar, are obtained in the e+e- centre-of-mass frame. As compared to distributions in the top rest frame, these have the advantage that they would allow direct comparison with experiment without the need to reconstruct the top rest frame. The results also do not depend on the choice of a spin quantization axis for t or tbar. Analytic expression for the triple distribution in the polar angle of t and polar and azimuthal angles of the lepton is obtained. Analytic expression is also derived for the distribution in the charged-lepton polar angle. Numerical values are discussed for total c.m. energies of 400 GeV, 800 GeV and 1500 GeV.Comment: 21 pages, Latex, 6 figures included in the submission. To appear in Pramana - Journal of Physics; expanded version of hep-ph/0011321, v

Rhomboid family member 2 regulates cytoskeletal stress-associated Keratin 16.

Keratin 16 (K16) is a cytoskeletal scaffolding protein highly expressed at pressure-bearing sites of the mammalian footpad. It can be induced in hyperproliferative states such as wound healing, inflammation and cancer. Here we show that the inactive rhomboid protease RHBDF2 (iRHOM2) regulates thickening of the footpad epidermis through its interaction with K16. K16 expression is absent in the thinned footpads of irhom2-/- mice compared with irhom2+/+mice, due to reduced keratinocyte proliferation. Gain-of-function mutations in iRHOM2 underlie Tylosis with oesophageal cancer (TOC), characterized by palmoplantar thickening, upregulate K16 with robust downregulation of its type II keratin binding partner, K6. By orchestrating the remodelling and turnover of K16, and uncoupling it from K6, iRHOM2 regulates the epithelial response to physical stress. These findings contribute to our understanding of the molecular mechanisms underlying hyperproliferation of the palmoplantar epidermis in both physiological and disease states, and how this 'stress' keratin is regulated