1.3 Facilities and the Relationship Between Home
Laboratory and Synchrotron
Nowadays many chemistry disciplines are utterly reliant on structural information to
understand the complexity of a system or how it functions. These disciplines can
produce very challenging samples for single-crystal diffraction, and also often it is
not possible to recrystallise them or refine the synthesis method to generate larger
crystals. Often these samples exceed the capability of local, traditional crystallographic facilities and recourse to larger-scale centralised facilities, and the appropriate expertise to handle such challenges is invaluable. To address these requirements
of modern chemistry, the UK has a ‘three-tiered’ model (1 ¼ ‘home laboratory’; 2 ¼
‘National Service laboratory’; 3 ¼ ‘synchrotron facility’). This means that weak
diffractors can be screened on the most powerful laboratory source available before
being referred to the synchrotron and ensures that the right samples are matched to
the correct facility. This means that as we approach the diffraction limit for crystals
of particular types of chemical systems, it is still possible to get structural
information.
The suitability of a facility to particular samples is not only important for
efficiency, but also we are now observing severe radiation damage for a significant
proportion of samples investigated at a third-generation synchrotron [53]. In fact, it
has been observed that samples previously considered to be ‘radiation hard’ are in
fact affected by the radiation doses that modern synchrotrons generate. In some more
extreme cases, there is clear evidence that the chemical makeup of a material can
change as a result of exposure to this level of dose, i.e. the structure is not the same
material at the end of the experiment as it was in the beginning. It is therefore now
becoming necessary to adopt the approaches that the protein crystallography community have taken to address this problem [54] and the interplay between the home
laboratory and synchrotron source will become crucial for successful data collection
in certain cases.
A comparison between the two facilities several years ago [11] showed that a
routine data collection with images collected at 1 s each on the attenuated synchrotron source is approximately equivalent to a 30 s per image data collection on the
NCS state-of-the-art instrument at that time. Final R-factors for data merging and
structure refinements were very comparable, so when taking into account the
difference in time factor and attenuation applied, the synchrotron was collecting
comparable data 100 times faster than the home laboratory. In the intervening time,
both facilities have upgraded instrumentation – with the home laboratory installing a
new HPC detector and the synchrotron upgrading the monochromator and goniometer and changing to a HPC detector.
Leading Edge Chemical Crystallography Service Provision and Its Impact on. . .
91
Laboratory and Synchrotron
Nowadays many chemistry disciplines are utterly reliant on structural information to
understand the complexity of a system or how it functions. These disciplines can
produce very challenging samples for single-crystal diffraction, and also often it is
not possible to recrystallise them or refine the synthesis method to generate larger
crystals. Often these samples exceed the capability of local, traditional crystallographic facilities and recourse to larger-scale centralised facilities, and the appropriate expertise to handle such challenges is invaluable. To address these requirements
of modern chemistry, the UK has a ‘three-tiered’ model (1 ¼ ‘home laboratory’; 2 ¼
‘National Service laboratory’; 3 ¼ ‘synchrotron facility’). This means that weak
diffractors can be screened on the most powerful laboratory source available before
being referred to the synchrotron and ensures that the right samples are matched to
the correct facility. This means that as we approach the diffraction limit for crystals
of particular types of chemical systems, it is still possible to get structural
information.
The suitability of a facility to particular samples is not only important for
efficiency, but also we are now observing severe radiation damage for a significant
proportion of samples investigated at a third-generation synchrotron [53]. In fact, it
has been observed that samples previously considered to be ‘radiation hard’ are in
fact affected by the radiation doses that modern synchrotrons generate. In some more
extreme cases, there is clear evidence that the chemical makeup of a material can
change as a result of exposure to this level of dose, i.e. the structure is not the same
material at the end of the experiment as it was in the beginning. It is therefore now
becoming necessary to adopt the approaches that the protein crystallography community have taken to address this problem [54] and the interplay between the home
laboratory and synchrotron source will become crucial for successful data collection
in certain cases.
A comparison between the two facilities several years ago [11] showed that a
routine data collection with images collected at 1 s each on the attenuated synchrotron source is approximately equivalent to a 30 s per image data collection on the
NCS state-of-the-art instrument at that time. Final R-factors for data merging and
structure refinements were very comparable, so when taking into account the
difference in time factor and attenuation applied, the synchrotron was collecting
comparable data 100 times faster than the home laboratory. In the intervening time,
both facilities have upgraded instrumentation – with the home laboratory installing a
new HPC detector and the synchrotron upgrading the monochromator and goniometer and changing to a HPC detector.
Leading Edge Chemical Crystallography Service Provision and Its Impact on. . .
91