macromolecular crystallographers work. However chemical crystallography has a
lot to benefit from by adopting fast diffraction screening. Traditionally this process
has been one of taking a single diffraction snapshot and assessing quality by eye or
by performing a short pre-experiment (typically 2 or 3 small scans) and judging the
accuracy of the indexed unit cell. However, with state-of-the-art hardware coupled
with well-developed software, new approaches are possible. It is now possible to
automatically process, solve and refine data as it is being collected. Accordingly, the
NCS screening procedure is now typically just to begin data collection and assess the
structure as it progresses. This is made viable due to the fact that an HPC detector
coupled with an intense X-ray source can collect data very quickly. Furthermore,
part of the CrysAlisPro software [46], Autochem, provides the ‘What is this?’
routine, which automatically integrates, solves and refines the structure from the
very beginning of a data collection. Typically, for a well-diffracting sample, an
initial structure is available in around 2 min, and from this, it is possible to much
better assess sample quality than by using traditional methods. For a challenging
case, several samples will be trialled in this way and then the best one selected for
data collection. This approach has not impacted the throughput of the facility, while
at the same time it has considerably improved the quality of structure that one would
typically get from such challenging samples.
On beamline I19 at Diamond, the software tool screen19 has been developed to
indicate whether count rate saturation has occurred for the Pilatus 2 M detector from
a short, fine-sliced, data collection scan. It provides an estimate of the level of beam
attenuation required to bring the count rate of the strongest reflections to below the
required threshold based on an estimate of the mosaic width of the reflections. The
program also indexes the observed reflections, to provide unit cell information, and
provides a Wilson plot so that an estimate can be made of the maximum resolution
that the sample diffracts to. The screen19 program is launched automatically for
each scan in any subsequent full data collection so that any degradation in the sample
quality can be assessed. In parallel, the autoprocessing pipeline will provide a solved
structure for each scan, or group of scans, used in the data collection, including the
scan used for initial screening.
Remote Access
The use of remote access in small molecule crystallography is still very much in its
infancy, and many of the techniques that have been implemented so far have been
borrowed heavily from macromolecular crystallography, where remote access is
now the exclusive mode of operation. In the paper of Johnson et al. [47], an excellent
account is given of the development of the remote operation of beamline I19, at
Diamond Light Source, for chemical crystallography studies. In their account, they
have identified the following key areas:
Sample Loading and Transportation The preparation and mounting of samples
have generally evolved in most chemical crystallography laboratories away from
86
S. J. Coles et al.
lot to benefit from by adopting fast diffraction screening. Traditionally this process
has been one of taking a single diffraction snapshot and assessing quality by eye or
by performing a short pre-experiment (typically 2 or 3 small scans) and judging the
accuracy of the indexed unit cell. However, with state-of-the-art hardware coupled
with well-developed software, new approaches are possible. It is now possible to
automatically process, solve and refine data as it is being collected. Accordingly, the
NCS screening procedure is now typically just to begin data collection and assess the
structure as it progresses. This is made viable due to the fact that an HPC detector
coupled with an intense X-ray source can collect data very quickly. Furthermore,
part of the CrysAlisPro software [46], Autochem, provides the ‘What is this?’
routine, which automatically integrates, solves and refines the structure from the
very beginning of a data collection. Typically, for a well-diffracting sample, an
initial structure is available in around 2 min, and from this, it is possible to much
better assess sample quality than by using traditional methods. For a challenging
case, several samples will be trialled in this way and then the best one selected for
data collection. This approach has not impacted the throughput of the facility, while
at the same time it has considerably improved the quality of structure that one would
typically get from such challenging samples.
On beamline I19 at Diamond, the software tool screen19 has been developed to
indicate whether count rate saturation has occurred for the Pilatus 2 M detector from
a short, fine-sliced, data collection scan. It provides an estimate of the level of beam
attenuation required to bring the count rate of the strongest reflections to below the
required threshold based on an estimate of the mosaic width of the reflections. The
program also indexes the observed reflections, to provide unit cell information, and
provides a Wilson plot so that an estimate can be made of the maximum resolution
that the sample diffracts to. The screen19 program is launched automatically for
each scan in any subsequent full data collection so that any degradation in the sample
quality can be assessed. In parallel, the autoprocessing pipeline will provide a solved
structure for each scan, or group of scans, used in the data collection, including the
scan used for initial screening.
Remote Access
The use of remote access in small molecule crystallography is still very much in its
infancy, and many of the techniques that have been implemented so far have been
borrowed heavily from macromolecular crystallography, where remote access is
now the exclusive mode of operation. In the paper of Johnson et al. [47], an excellent
account is given of the development of the remote operation of beamline I19, at
Diamond Light Source, for chemical crystallography studies. In their account, they
have identified the following key areas:
Sample Loading and Transportation The preparation and mounting of samples
have generally evolved in most chemical crystallography laboratories away from
86
S. J. Coles et al.