Molecular dynamics simulation on a parallel computer

For the purpose of molecular dynamics simulations of large biopolymers we have built a parallel computer with a systolic loop architecture, based on Transputers as computational units, and have programmed it in occam II. The computational nodes of the computer are linked together in a systolic ring. The program based on this-topology for large biopolymers increases its computational throughput nearly linearly with the number of computational nodes. The program developed is closely related to the simulation programs CHARMM and XPLOR, the input files required (force field, protein structure file, coordinates) and output files generated (sets of atomic coordinates representing dynamic trajectories and energies) are compatible with the corresponding files of these programs. Benchmark results of simulations of biopolymers comprising 66, 568, 3 634, 5 797 and 12 637 atoms are compared with XPLOR simulations on conventional computers (Cray, Convex, Vax). These results demonstrate that the software and hardware developed provide extremely cost effective biopolymer simulations. We present also a simulation (equilibrium of X-ray structure) of the complete photosynthetic reaction center of Rhodopseudomonas viridis (12 637 atoms). The simulation accounts for the Coulomb forces exactly, i.e. no cut-off had been assumed.