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Nucleation<br />
Nucleation as a pre-requisite for the<br />
crystallization of proteins can be<br />
considered as a special case of selfassociation.<br />
Using sedimentation<br />
velocity experiments performed under<br />
crystallization conditions, we were<br />
able to detect oligomers of 15-20<br />
protein molecules. These complexes<br />
or nuclei can grow spontaneously to<br />
crystals in supersaturated solution.<br />
Crystallization conditions are often far<br />
from the pI, where proteins are either<br />
polyanions or polycations. The high<br />
net charge, as reflected by nonideality<br />
data (second virial coefficient), can<br />
prevent oligomerization. By addition<br />
of neutral salts the charges are<br />
screened resulting in a reduction in<br />
repulsion between the protein<br />
molecules and the possibility of<br />
forming associates. The conditions<br />
necessary for protein crystallization<br />
can be derived from the value of the<br />
virial coefficient or the ratio of the<br />
excluded volume and the chargedependent<br />
part of this parameter.<br />
Selected Publications<br />
Behlke, J., and Ristau, O. (1998) An<br />
improved approximate solution of the<br />
Lamm equation for the simultaneous<br />
estimation of sedimentation and<br />
diffusion coefficients from<br />
sedimentation velocity experiments.<br />
Biophys. Chem. 70, 133-146.<br />
Behlke, J., Heidrich, K., Naumann,<br />
M., Müller, E.-C., Otto, A., Reuter, R.,<br />
and Kriegel, T. (1998) Hexokinase 2<br />
from Saccharomyces cerevisiae:<br />
Regulation of oligomeric structure by<br />
in-vivo phosphorylation at serine-14.<br />
Biochemistry 37, 11989-11995.<br />
Behlke, J., and Ristau O. (1998) Gross<br />
conformation of dissolved angiotensin<br />
derived from sedimentation and<br />
diffusion coefficients. Biochem. Soc.<br />
Trans. 26, 758-761.<br />
Schade, M., Behlke, J., Löwenhaupt,<br />
K., Herbert, A. Rich, A., and<br />
Oschkinat, H. (1999) A 6 basepair Z-<br />
DNA hairpin binds two Z domains<br />
from the human RNA editing enzyme.<br />
ADAR1. FEBS Letters 458, 27-31.<br />
Behlke, J., and Ristau O. (1999)<br />
Analysis of the thermodynamic nonideality<br />
of proteins by sedimentation<br />
equilibrium experiments. Biophys.<br />
Chem. 76, 13-23.<br />
Structure of the Group<br />
Group leader<br />
Prof. Dr. Joachim Behlke<br />
Scientist<br />
Dr. Otto Ristau*<br />
Technical assistant<br />
Bärbel Bödner<br />
*part of period reported<br />
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