This title appears in the Scientific Report :
2017
Please use the identifier:
http://hdl.handle.net/2128/13914 in citations.
Change of Fractal Dimension during the early stages ofLysozyme Crystallization
Change of Fractal Dimension during the early stages ofLysozyme Crystallization
Neutron protein crystallography is a powerful tool to investigate enzyme mechanisms in depth. It has the advantage of providing also the hydrogen atom positions which are practically invisible in x-ray crystallography. Furthermore, it does not lead to a reduction of the active center due to radiatio...
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Personal Name(s): | Heigl, Raimund |
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Stellbrink, Jörg / Radulescu, Aurel / Schweins, Ralf / Schrader, Tobias Erich (Corresponding author) / Richter, Dieter | |
Contributing Institute: |
Streumethoden; JCNS-2 Neutronenstreuung; JCNS-1 JCNS-FRM-II; JCNS-FRM-II |
Imprint: |
2016
|
Conference: | German Conference on Neutron Scattering 2016, Kiel (Germany), 2016-09-20 - 2016-09-22 |
Document Type: |
Poster |
Research Program: |
Neutron Scattering and Muon Spectroscopy Integrated Initiative Jülich Centre for Neutron Research (JCNS) Soft Matter, Health and Life Sciences FRM II / MLZ |
Subject (ZB): | |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
Neutron protein crystallography is a powerful tool to investigate enzyme mechanisms in depth. It has the advantage of providing also the hydrogen atom positions which are practically invisible in x-ray crystallography. Furthermore, it does not lead to a reduction of the active center due to radiation damage often encountered using x-rays. Its main disadvantage is the need for rather large crystals (> 0.5 mm3). This proves to be the biggest bottle-neck when considering a neutron protein crystallography experiment. To address this we concentrated on the early stages of the crystallization process where the directions are set whether many small crystals grow or few large ones. We used lysozyme as a model system since it has been studied well in the past and the phase diagram of its crystal growth is known. We used a combination of three scattering techniques since the involved size ranges require a large q-range. Small angle neutron scattering was used in combination with static light scattering on the same sample in order to obtain structural information on the growing crystal seeds. In situ dynamic light scattering at the neutron scattering sample cell was used to obtain an overview of all sizes present in the crystallization process by measuring their hydrodynamic radii. The small angle neutron scattering technique requires the crystallization in heavy water instead of normal water. We found that the crystallization conditions did not differ too much from the ones mentioned in the literature for light water when using a corrected pD value of pD=pH+0.4. The crystallization is initiated by mixing a 60 mg/ml Lysozyme solution with a 6 wt% NaCl acetate buffer solution (both at pD=4.75 and at 298 K) in a 1:1 ratio. Immediately after mixing, dimers of lysozyme molecules are formed and the structure factor seen in the lysozyme stock solution disappears. Under the chosen conditions we could observe a fractal growth of the crystal seeds with a change of the fractal dimension from 1.0 to 1.7 in the first 90 min. This can be interpreted as a crystal seed being formed first which grows more in a linear manner with little branching. Later, the space in between the branched arms is filled to cross over to a more densely packed fractal. With these results theoretical models of crystal growth can be improved. Furthermore, the early detection of crystal seeds can be used to rapidly change the crystallization conditions (e. g. temperature) in order to avoid the production of more crystal seeds. |