29,102 research outputs found
In silico Protein Structural Modeling and Active binding site Evaluation of Streptococcus pneumoniae
Structure function relation of glucose kinese in Streptococcus pneumoniae. However, a solved structure for _Streptococcus pneumoniae_ glucose kinese is not available at the protein data bank. Glucose kinase is a regulatory enzyme capable of adding phosphate group to glucose in the first step of streptomycin biosynthesis. The activity of glucose kinase was regulated by the Carbon Catabolite Repression system. So, we created a model of glucose kinese from _Streptococcus pnemoniae_ using the X-ray crystallography structure of glucose kinese enzymes from _Enterobacteria faecalis_ as template with Molsoft ICM v3.5 software. The model was validated using protein structure checking tools such as PROCHECK, WHAT IF: for reliability. The active site amino acid "Asp114" in the template is retained in _S. pneumoniae_ Glucose kinese model "Asp115". Solvent accessible surface area analysis of the glucose kinese model showed that known key residues playing important role in active site for ligand binding and metal ion binding are buried and hence not accessible to solvent. The information thus discussed provides insight to the molecular understanding of _Streptococcus pneumoniae_ in glucose kinase
Curvature Inspired Cosmological Scenario
Using modified gravity with non-linear terms of curvature, and (with being the positive real number and being the scalar
curvature), cosmological scenario,beginning at the Planck scale, is obtained.
Here, a unified picture of cosmology is obtained from gravity. In this
scenario, universe begins with power-law inflation, followed by deceleration
and acceleration in the late universe as well as possible collapse of the
universe in future. It is different from dark energy models with
non-linear curvature terms assumed as dark energy. Here, dark energy terms are
induced by linear as well as non-linear terms of curvature in Friedmann
equation being derived from modified gravity.It is also interesting to see
that, in this model, dark radiation and dark matter terms emerge spontaneously
from the gravitational sector. It is found that dark energy, obtained here,
behaves as quintessence in the early universe and phantom in the late universe.
Moreover, analogous to brane-tension in brane-gravity inspired Friedmann
equation, a tension term arises here being called as cosmic tension.
It is found that, in the late universe, Friedmann equation (obtained here)
contains a term ( being the phantom energy density)
analogous to a similar term in Friedmann equation with loop quantum effects, if
and brane-gravity correction when Comment: 19 Pages. To appear in Int. J. Thro. Phy
Picard-Fuchs Ordinary Differential Systems in N=2 Supersymmetric Yang-Mills Theories
In general, Picard-Fuchs systems in N=2 supersymmetric Yang-Mills theories
are realized as a set of simultaneous partial differential equations. However,
if the QCD scale parameter is used as unique independent variable instead of
moduli, the resulting Picard-Fuchs systems are represented by a single ordinary
differential equation (ODE) whose order coincides with the total number of
independent periods. This paper discusses some properties of these Picard-Fuchs
ODEs. In contrast with the usual Picard-Fuchs systems written in terms of
moduli derivatives, there exists a Wronskian for this ordinary differential
system and this Wronskian produces a new relation among periods, moduli and QCD
scale parameter, which in the case of SU(2) is reminiscent of scaling relation
of prepotential. On the other hand, in the case of the SU(3) theory, there are
two kinds of ordinary differential equations, one of which is the equation
directly constructed from periods and the other is derived from the SU(3)
Picard-Fuchs equations in moduli derivatives identified with Appell's
hypergeometric system, i.e., Burchnall's fifth order ordinary differential
equation published in 1942. It is shown that four of the five independent
solutions to the latter equation actually correspond to the four periods in the
SU(3) gauge theory and the closed form of the remaining one is established by
the SU(3) Picard-Fuchs ODE. The formula for this fifth solution is a new one.Comment: \documentstyle[12pt,preprint,aps,prb]{revtex}, to be published in J.
Math. Phy
On the Production of Flux Vortices and Magnetic Monopoles in Phase Transitions
We examine the basic assumptions underlying a scenario due to Kibble that is
widely used to estimate the production of topological defects. We argue that
one of the crucial assumptions, namely the geodesic rule, although completely
valid for global defects, becomes ill defined for the case of gauged defects.
We address the issues involved in formulating a suitable geodesic rule for this
case and argue that the dynamics plays an important role in the production of
gauge defects.Comment: 9 pages, in LATEX, UMN-TH-1028/92, TPI-MINN-92/20-
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