Change of Fractal Dimension during the early stages of Lysozyme Crystallization

In this study we focussed on the question of how to grow crystals as large as possible in light of their use as samples for neutron protein crystallography. We investigated the early stages of the crystallisation process where the directions are set between the growth of many small crystals or few large ones. We used lysozyme since it is considered as a model system for crystal growth. Small angle neutron scattering was used in combination with static light scattering in order to realize an extended q-range. In situ dynamic light scattering at the neutron scattering sample cell was used to obtain an overview of all sizes present in the crystallisation process. We could observe a fractal growth of the crystal seeds with a change in the fractal dimension from 1.0 to 1.7 in the first 90 min. This can be interpreted that at first a branched crystal seed is formed which grows more in a linearly. Later, the space between the arms is filled to cross over to a more densely packed fractal

In-situ light scattering at neutron beam lines - experiences made and challenges ahead

What is often well established at many synchrotron beam lines is still in the development phase at neutron beam lines: In-situ light scattering techniques. The science case for in-situ light scattering at neutron instruments lies mostly in the limited reproducibility of sample preparation and stability of the samples over time. Whereas many soft matter or hard matter samples are not transparent for light, many biological samples often show a sufficiently broad spectral range where light absorption does not play a dominant role. Natural candidates for neutron instruments to be equipped with in-situ light scattering techniques are small angle scattering, spin echo, time-of-flight and backscattering beam lines. We routinely supply in-situ dynamic light scattering with one fixed scattering angle at the instrument KWS-2 at MLZ to users who would like to control their sample during the neutron measurement. Recently, we have successfully tested a three angle dynamic light scattering set-up at KWS-2. For the Jülich neutron spin echo spectrometer we are currently developing a prototype sample environment which includes two scattering angles and a transmission detector. The transmission detector reports on a change in turbidity with a very high time resolution. This is especially attractive to thermoresponsive soft matter samples with a very narrow transition from a swollen to a more compact micellar state

In-situ light scattering at neutron beam lines - experiences made and challenges ahead

What is often well established at many synchrotron beam lines is still in the development phase at neutron beam lines: In-situ light scattering techniques. The science case for in-situ light scattering at neutron instruments lies mostly in the limited reproducibility of sample preparation and stability of the samples over time. Whereas many soft matter or hard matter samples are not transparent for light, many biological samples often show a sufficiently broad spectral range where light absorption does not play a dominant role. Natural candidates for neutron instruments to be equipped with in-situ light scattering techniques are small angle scattering, spin echo, time-of-flight and backscattering beam lines. We routinely supply in-situ dynamic light scattering with one fixed scattering angle at the instrument KWS-2 at MLZ to users who would like to control their sample during the neutron measurement. Recently, we have successfully tested a three angle dynamic light scattering set-up at KWS-2. For the Jülich neutron spin echo spectrometer we are currently developing a prototype sample environment which includes two scattering angles and a transmission detector. The transmission detector reports on a change in turbidity with a very high time resolution. This is especially attractive to thermoresponsive soft matter samples with a very narrow transition from a swollen to a more compact micellar state