Filtering by
- Resource Type: Text
The availability of X-ray free electron lasers presents an opportunity to study micron-sized crystals that could be triggered (using light, small molecules or physical conditions) to capture macromolecules in action. This method of ‘Time-resolved serial crystallography’ answers key biological questions by capturing snapshots of conformational changes associated with multi-step reactions. This dissertation describes approaches for studying structures of large membrane protein complexes. Both macro and micro-seeding techniques have been implemented for improving crystal quality and obtaining high-resolution structures. Well-diffracting 15-20 micron crystals of active Photosystem II were used to perform time-resolved studies with fixed-target Roadrunner sample delivery system. By employing continuous diffraction obtained up to 2 A, significant progress can be made towards understanding the process of water oxidation.
Structure of Photosystem I was solved to 2.3 A by X-ray crystallography and to medium resolution of 4.8 A using Cryogenic electron microscopy. Using complimentary techniques to study macromolecules provides an insight into differences among methods in structural biology. This helps in overcoming limitations of one specific technique and contributes in greater knowledge of the molecule under study.
X-ray free-electron lasers provide novel opportunities to conduct single particle analysis on nanoscale particles. Coherent diffractive imaging experiments were performed at the Linac Coherent Light Source (LCLS), SLAC National Laboratory, exposing single inorganic core-shell nanoparticles to femtosecond hard-X-ray pulses. Each facetted nanoparticle consisted of a crystalline gold core and a differently shaped palladium shell. Scattered intensities were observed up to about 7 nm resolution. Analysis of the scattering patterns revealed the size distribution of the samples, which is consistent with that obtained from direct real-space imaging by electron microscopy. Scattering patterns resulting from single particles were selected and compiled into a dataset which can be valuable for algorithm developments in single particle scattering research.