10,490 research outputs found
Generating functional analysis of complex formation and dissociation in large protein interaction networks
We analyze large systems of interacting proteins, using techniques from the
non-equilibrium statistical mechanics of disordered many-particle systems.
Apart from protein production and removal, the most relevant microscopic
processes in the proteome are complex formation and dissociation, and the
microscopic degrees of freedom are the evolving concentrations of unbound
proteins (in multiple post-translational states) and of protein complexes. Here
we only include dimer-complexes, for mathematical simplicity, and we draw the
network that describes which proteins are reaction partners from an ensemble of
random graphs with an arbitrary degree distribution. We show how generating
functional analysis methods can be used successfully to derive closed equations
for dynamical order parameters, representing an exact macroscopic description
of the complex formation and dissociation dynamics in the infinite system
limit. We end this paper with a discussion of the possible routes towards
solving the nontrivial order parameter equations, either exactly (in specific
limits) or approximately.Comment: 14 pages, to be published in Proc of IW-SMI-2009 in Kyoto (Journal of
Phys Conference Series
Chiral Symmetry and s-wave Low-Lying Meson-Baryon Resonances
The wave meson-baryon scattering is analyzed for the isospin-strangeness
and sectors, in a Bethe-Salpeter coupled channel
formalism incorporating Chiral Symmetry. For both sectors, four channels have
been considered: , , , and ,
, , , respectively. The needed two particle
irreducible matrix amplitudes are taken from lowest order Chiral Perturbation
Theory in a relativistic formalism. There appear undetermined low energy
constants, as a consequence of the renormalization of the amplitudes, which are
obtained from fits to the available data: elastic phase-shifts, and cross sections and to
mass-spectrum, the elastic and
--matrices and to the
cross section data. The position and residues of the complex poles in the
second Riemann sheet of the scattering amplitude determine masses, widths and
branching ratios of the (1535) and (1650) and
(1405) and (1670) resonances, in reasonable agreement with
experiment. A good overall description of data, from threshold up to around 2
GeV is achieved despite the fact that three-body channels have not been
explicitly included.Comment: 5 Pages, 2 figures, invited contribution to Focus Session on Nature
of Threshold N*, to be published in Proceedings of Nstar 2002, Pittsburgh,
USA, October 9-12, 2002 (World Scientific
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