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632. Implementation and Use of the Method of Prudent Ascent
in Conformational Analysis Using Molecular Mechanics
by Rob W. W. Hooft, Jan A. Kanters, Jan Kroon,
Department of Crystal and Structural Chemistry, Bijovet
Center for Biomolecular Research, University of
Utrecht, Padualaan 8, NL-3584 CH Utrecht, The
Netherlands
The current practice in two-dimensional conformational
analysis is to perform an energy minimisation for all
possible combinations of two dihedral angles in the
molecule, in a fixed order, and applying a certain
dihedral angle step-size.
A newly developed method is presented in which the
order of the evaluation of points on the energy-surface
is not fixed but is dependent on all previous results
in a way which we call "the method of prudent ascent".
In this method the most promising calculation is
carried out first, thus minimising the risk of atomic
collisions.
In order to be able to take care of the many additional
degrees of conformational freedom present in, e.g.,
carbohydrate molecules, all minimisations are performed
using a set of different promising starting
conformations on the basis of previous calculations,
and only the lowest energy result for each point is
saved.
An application of the method to conformational analysis
of methylcellobiose and the artificial sweetener
trichlorogalactosucrose is also presented.
NOTE:This program is a general purpose energy
minimizer. It is set up at the moment using the
MM3 system to provide energy points. Before we
distribute the system, we will remove the MM3
software. We will leave references to directories
which would be found in MM3, but the directories
will be empty, as MM3 is a proprietary program.
The references are being left
so that a user would know where to install his
program forgenerating energy points.
Conceptually, one could use MOPAC to generate
single energy points, and then a geometry could be
optimized using this system.
Lines of Code: 3034
FORTRAN 77 (VAX)
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