TOWARDS THE COMPLETE CLASSIFICATION
OF PROTEIN NATIVE STATE CONFORMATIONAL DIVERSITY
The traditional objective in the computational
investigation of protein structure is to locate a single conformation at
the global minimum in the potential energy. It was commonly believed that
the native state of a protein lies at that position on the energy surface.
In recent developments it is now believed to be necessary to characterize
the distribution of conformations of a protein active site, not just the
single conformation at the global minimum.
A further difficulty is the inefficiency
of the widely used simulated annealing method when employed to optimize
the structures of proteins, especially those which exhibit a frustrated
energy landscape. An exhaustive search of parameter space in such systems
is unfeasible, so it is typical for only a handful of runs to be performed
on a reasonably sized protein. Even allowing for advances in high performance
computer technology and for the development of more efficient Monte Carlo
optimization algorithms, it is likely that the problem of incomplete energy
distributions and qualitative characterization of low-energy conformations
will persist for the foreseeable future.
Recently we published a pattern recognition
technique, “histogram filtering” [Ref. 56] with which to optimize parameters
in wave functions for use in quantum Monte Carlo simulations. We are exploiting
histogram filtering in conjunction with cluster analysis to a) characterize
the low-energy local minimum energy structures, and b) to arrive at a complete
description of the distribution of conformations for proteins, without
having to take recourse to a very large number of simulated annealing runs.
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