title: Diffraction and imaging from a beam of laser-aligned proteins: resolution limits.
abstract: The effect of the limited alignment of hydrated molecules is considered in a laser-aligned molecular beam, on diffraction patterns taken from the beam. Simulated patterns for a protein beam are inverted using the Fienup-Gerchberg-Saxton phasing algorithm, and the effect of limited alignment on the resolution of the resulting potential maps is studied. For a typical protein molecule (lysozyme) with anisotropic polarizability, it is found that up to 1 kW of continuous-wave near-infrared laser power (depending on dielectric constant), together with cooling to liquid-nitrogen temperatures, may be needed to produce sufficiently accurate alignment for direct observation of the secondary structure of proteins in the reconstructed potential or charge-density map. For a typical virus (TMV), a 50 W continuous-wave laser is adequate for subnanometre resolution at room temperature. The dependence of resolution on laser power, temperature, molecular size, shape and dielectric constant is analyzed.
authors.affiliation: Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA. spence@asu.edu
authors.forename: J C H
authors.initials: JC
authors.lastname: Spence
authors.forename: K
authors.initials: K
authors.lastname: Schmidt
authors.forename: J S
authors.initials: JS
authors.lastname: Wu
authors.forename: G
authors.initials: G
authors.lastname: Hembree
authors.forename: U
authors.initials: U
authors.lastname: Weierstall
authors.forename: B
authors.initials: B
authors.lastname: Doak
authors.forename: P
authors.initials: P
authors.lastname: Fromme
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D007091:Image Processing, Computer-Assisted; D007834:Lasers; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D055672:Static Electricity; D013696:Temperature; D014027:Tobacco Mosaic Virus / Q000737:chemistry / Q000648:ultrastructure; D014961:X-Ray Diffraction / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D011506:Proteins; D009113:Muramidase