Dynamic Light Scattering Investigation in Aqueous Solutions of bc1-Complex Membrane Protein - Analytical Methods & Tools for Lyophilization

Dynamic Light Scattering Investigation in Aqueous Solutions of bc1-Complex Membrane Protein
Received: November 29, 2001
In Final Form: February 12, 2002
Web Release Date: March 30, 2002
Kazuo Onuma,* Tomomi Kubota, Shinpei Tanaka, Noriko Kanzaki, Atsuo Ito, and Kazunori Tsutsui
J. Phys. Chem
ACS Publications
Copyright ? 2002 American Chemical Society
Tissue Engineering Research Center, National Institute of Advanced Industrial Science and Technology, Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan, Institute of Molecular and Cell Biology, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8568, Japan, Special Division for Human Life Technology, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan, and Otsuka Electronics Company, Ltd., 3-26-3, Shodai-Tajika, Hirakata, Osaka 573-1132, Japan
Abstract:
The hydrodynamic radius of a membrane protein, bc1-complex, in aqueous solutions was investigated using a dynamic light scattering technique. The essential unit in the solutions was found to take the dimer form of bc1-complex molecules. The aggregates exceeding 100 nm appeared with an increase in the crystallizing reagent, PEG, and the precipitation of an amorphous phase was observed. This feature was characteristic of zinc-free solutions. When 2 mM zinc was in the solutions, large aggregates of proteins were not observed, and single crystals of bc1-complex directly nucleated when the PEG concentration reached a critical level. The mutual diffusion coefficient of the dimers in the zinc-free solutions decreased with an increase in the protein concentration when the concentration of PEG was constant, indicating an attractive force between molecules. When the solution contained zinc, the coefficient increased with an increase in the protein concentration, indicating a repulsive force between molecules.
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