3,323 research outputs found
Characterization of pyridine nucleotide binding site of UDP-glucose 4-epimerase from Saccharomyces fragilis
UDP-glucose 4-epimerase from Saccharomyces fragilis has 1 mol of NAD firmly bound per mol of the dimeric apoenzyme. This prevents a direct study of the coenzyme binding site of the protein. Dissociation of the dimer with p-chloromercuribenzoate and its reconstitution with exogenous NAD or one of its analogues and 2-mercaptoethanol provides an indirect method of study of the site. Depending on the reconstitution properties, the analogues can be classified in the following groups: (i) analogues that have no affinity for the site; (ii) analogues that have affinity but are not incorporated into the apoenzyme; (iii) analogues that produce catalytically inactive holoenzymes; and (iv) analogues that produce catalytically active holoenzymes. Minimum structural requirements that lead to affinity for the coenzyme site and to binding to the apoenzyme can also be discerned from these studies. Reconstitution with etheno-NAD, a fluorescent analogue of NAD, indicates the presence of a hydrophobic pocket for the adenosine subsite
Study on Noncommutative Representations of Galilean Generators
The representations of Galilean generators are constructed on a space where
both position and momentum coordinates are noncommutating operators. A
dynamical model invariant under noncommutative phase space transformations is
constructed. The Dirac brackets of this model reproduce the original
noncommutative algebra. Also, the generators in terms of noncommutative phase
space variables are abstracted from this model in a consistent manner. Finally,
the role of Jacobi identities is emphasised to produce the noncommuting
structure that occurs when an electron is subjected to a constant magnetic
field and Berry curvature.Comment: Title changed, new references added, published in Int. J. Mod. Phys.
Many-body localized to ergodic transitions in a system with correlated disorder
We study the transition from a many-body localized phase to an ergodic phase in spin chain with correlated random magnetic fields. Using multiple statistical measures like gap statistics and extremal entanglement spectrum distributions, we find the phase diagram in the disorder-correlation plane, where the transition happens at progressively larger values of the correlation with increasing values of disorder. We then show that one can use the average of sample variance of magnetic fields as a single parameter which encodes the effects of the correlated disorder. The distributions and averages of various statistics collapse into a single curve as a function of this parameter. This also allows us to analytically calculate the phase diagram in the disorder-correlation plane
Violation of Bell's inequality for phase singular beams
We have considered optical beams with phase singularity and experimentally
verified that these beams, although being classical, have properties of two
mode entanglement in quantum states. We have observed the violation of Bell's
inequality for continuous variables using the Wigner distribution function
(WDF) proposed by Chowdhury et al. [Phys. Rev. A \textbf{88}, 013830 (2013)].
Our experiment establishes a new form of Bell's inequality in terms of the WDF
which can be used for classical as well as quantum systems.Comment: 7 pages, 9 figures and 1 tabl
Non equilibrium statistical physics with fictitious time
Problems in non equilibrium statistical physics are characterized by the
absence of a fluctuation dissipation theorem. The usual analytic route for
treating these vast class of problems is to use response fields in addition to
the real fields that are pertinent to a given problem. This line of argument
was introduced by Martin, Siggia and Rose. We show that instead of using the
response field, one can, following the stochastic quantization of Parisi and
Wu, introduce a fictitious time. In this extra dimension a fluctuation
dissipation theorem is built in and provides a different outlook to problems in
non equilibrium statistical physics.Comment: 4 page
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