Dynamic Light Scattering Investigation in Aqueous Solutions of bc₁-Complex Membrane Protein

Abstract

The hydrodynamic radius of a membrane protein, bc 1 -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 bc 1 -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 bc 1 -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.

Rationalization of Membrane Protein Crystallization with Polyethylene Glycol Using a Simple Depletion Model

“…The method of purification was reported elsewhere (Onuma et al, 2002). In the previous study, we showed that complex phenomena occurred during crystallization of BC1 where Zn ions played an important role (Onuma et al, 2002). In this study, however, we concentrated on PEG-induced attraction in simpler Zn-free solutions.…”

“…Bovine heart cytochrome bc 1 complex (BC1) was freshly prepared and used within two weeks to avoid denaturation. The method of purification was reported elsewhere (Onuma et al, 2002). In the previous study, we showed that complex phenomena occurred during crystallization of BC1 where Zn ions played an important role (Onuma et al, 2002).…”

Relationship between molecular weight of poly(ethylene)glycol and intermolecular interaction of Taka-amylase A monomers

“…This model predicted that the effect of PEG on the diffusion of protein would be smaller when the protein monomers were much larger than the PEG molecules. This was the case in previous studies [14,15] using bc1-complex membrane protein. The r H of bc1-complex is 7.2 nm, much larger than that of TAA monomers.…”

“…One way to avoid these behaviors in protein crystallization is to use poly(ethylene)glycol (PEG) [6][7][8][9][10][11][12][13][14][15]. Since PEG is a nonionic polymer, it does not directly affect the competition between electrostatic repulsion and van der Waals attraction.…”

Association of Calcium Phosphate and Fibroblast Growth Factor‐2: a Dynamic Light Scattering Study

“…DLS has been used by many researchers [17][18][19][20][21][22][23][24][25] to investigate protein solutions because it is convenient. FGF-2 solutions have been observed as a function of the concentration, salt content and time.…”