User Meeting 2014

Chemical Crystallography at the Australian Synchrotron MX Beamlines

20 Nov 2014, 15:50

20m

Oliphant Auditorium ()

Oral Beamlines, Instrumentation and Techniques Beamlines, Instrumentation and Techniques II

Speaker

Dr Jason Price (Australian Synchrotron)

Description

The Macromolecular Crystallography (MX) Beamlines at the Australian Synchrotron collect data on protein samples (PX) and chemical samples (CX). This broad range of sample types requires us to consider a number of experimental and data processing considerations. Protein samples have very large unit cells but diffract weakly, the chemical samples on the other hand have comparatively a very small unit cell, diffract much more strongly and to higher resolution. From an experimental point of view, this requires substantially different geometrical considerations which can be handled by changing the energy of the monochromated X-rays and detector distance. Another consideration is detector type, the detectors at the MX beamlines are from the Area Detector Systems Corporation (ADSC) and they have generally been used for PX data collections. As the detectors have mainly been used for PX work, the software for sample handling has also been developed with PX considerations rather than CX. For example, the XDS software for space group determinations is set by default to assume that the space group is only ever one of the 65 space groups that don’t contain mirror, inversion or glide operations. Another area of interest is the way data scaling (absorption) is handled. The data is often scaled with PX data for a number of reasons, with the most common scaling of data is due to the prevalence of radiation damage to the samples. By contrast the most common form of scaling for CX data is for sample anisotropy in strong absorbers.