title: Taking X-ray diffraction to the limit: macromolecular structures from femtosecond X-ray pulses and diffraction microscopy of cells with synchrotron radiation.
abstract: Recent work is extending the methodology of X-ray crystallography to the structure determination of noncrystalline specimens. The phase problem is solved using the oversampling method, which takes advantage of "continuous" diffraction patterns from noncrystalline specimens. Here we review the principle of this newly developed technique and discuss the ongoing experiments of imaging nonperiodic objects, such as cells and cellular structures, using coherent and bright X rays produced by third-generation synchrotron sources. In the longer run, the technique may be applicable to image single biomolecules using anticipated X-ray free electron lasers. Here, computer simulations have so far demonstrated two important steps: (a) by using an extremely intense femtosecond X-ray pulse, a diffraction pattern can be recorded from a macromolecule before radiation damage manifests itself; and (b) the phase information can be retrieved in an ab initio fashion from a set of calculated noisy diffraction patterns of single protein molecules.
authors.affiliation: Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309-0210, USA. miao@ssrl.slac.stanford.edu
authors.forename: Jianwei
authors.initials: J
authors.lastname: Miao
authors.forename: Henry N
authors.initials: HN
authors.lastname: Chapman
authors.forename: Janos
authors.initials: J
authors.lastname: Kirz
authors.forename: David
authors.initials: D
authors.lastname: Sayre
authors.forename: Keith O
authors.initials: KO
authors.lastname: Hodgson
mesh_terms: D000465:Algorithms; D002477:Cells / Q000648:ultrastructure*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D046911:Macromolecular Substances; D008854:Microscopy, Electron / Q000379:methods* / Q000639:trends; D011506:Proteins / Q000648:ultrastructure*; D012815:Signal Processing, Computer-Assisted; D014961:X-Ray Diffraction / Q000379:methods* / Q000639:trends
chemical_list: D046911:Macromolecular Substances; D011506:Proteins