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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) |