SUPERCOMPUTER SIMULATION OF SMALL-ANGLE X-RAY-SCATTERING, ELECTRON-MICROGRAPHS AND X-RAY-DIFFRACTION PATTERNS OF MACROMOLECULAR STRUCTURES

We describe two algorithms used in structural studies of proteins and macromolecular complexes. The first deals with simulation of Small Ang le X-ray Scattering patterns. An approximate representation of the Deb ye formula based on the discretized histogram of pair distances allows the SAXS calculation of large macromolecules modelled by thousands of spheres to be performed in a few minutes of CPU time. The second algo rithm concerns the computation of the mass projection of a structural model at a given projection angle. Such projections are used to reprod uce structural features observed in electron micrographs of large biol ogical structures. The accumulation of the Fourier transform intensity of mass projections of model structures for a series of angles is use d to simulate X-ray diffraction patterns. Both algorithms have been pa rallelised and implemented on the Intel iPSC/860 hypercube.