Electron Diffraction from a Low Temperature Oriented Molecular Beam

This invention is an apparatus which generates a beam of hydrated molecules at the temperature of liquid helium within a vacuum chamber. This beam passes through a laser beam, which rotates all the molecules into the same orientation. The beam then passes across a coherent electron beam which produces an electron diffraction pattern. The use of the apparatus is to solve the structure, at atomic resolution, of proteins and other molecules which do not readily form the crystals needed for X-ray crystallography. The structures are solved using these electron diffraction patterns and new iterative solutions to the phase problem, together with the heavy-atom method. Charge-density maps are obtained for many orientations of the molecule, and synthesized tomographically to generate a three-dimensional view.