Diffraction and imaging from a beam of laser-aligned proteins: resolution limits.
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.
Spence
J C H
JC
Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA. spence@asu.edu
Schmidt
K
K
Wu
J S
JS
Hembree
G
G
Weierstall
U
U
Doak
B
B
Fromme
P
P
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
D011506:Proteins; D009113:Muramidase