Partial specific volume and solvent interactions of amphipol A8-35

Amphipols are small amphiphilic polymers that can stabilize and keep soluble membrane proteins in aqueous solutions in the absence of detergent. A prerequisite to solution studies of membrane protein/amphipol complexes is the determination of the partial specific volume v ¯ 2 and effective charge z...

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Bibliographic Details
Published in:Analytical biochemistry 2004-11, Vol.334 (2), p.318-334
Main Authors: Gohon, Yann, Pavlov, Georgy, Timmins, Peter, Tribet, Christophe, Popot, Jean-Luc, Ebel, Christine
Format: Article
Language:English
Subjects:
Amphipol
Analytical ultracentrifugation
Carbon - analysis
Counter-ion dissociation
Density
Deuterium
Heparin - chemistry
Hydrogen - chemistry
Magnetic Resonance Spectroscopy
Molecular Structure
Molecular Weight
Polyelectrolyte
Polymers - chemistry
Propylamines - chemistry
Small-angle neutron scattering
Solvents - chemistry
Viscosity
Water - chemistry
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Summary:Amphipols are small amphiphilic polymers that can stabilize and keep soluble membrane proteins in aqueous solutions in the absence of detergent. A prerequisite to solution studies of membrane protein/amphipol complexes is the determination of the partial specific volume v ¯ 2 and effective charge z of the polymer. The ratio ( R) of the buoyant molar masses of particles in D 2O and H 2O solutions, obtained from sedimentation velocity ( s H/ s D method) and sedimentation equilibrium experiments, and their contrast match point (CMP), determined in small-angle neutron scattering experiments, depend on v ¯ 2 and z. When z is known, v ¯ 2 can be estimated from R with a good accuracy as long as v ¯ 2 is close to 1. The effects of labile H/D exchange and of polyelectrolyte counter-ion dissociation in general cannot be neglected. The accuracy, advantages, and limits of the s H/ s D method have been studied in details using model macromolecules (DNA, protein, and polysaccharide). The s H/ s D method appears particularly advantageous for the study of heterogeneous samples. Measurements of density, s D/s H buoyant molar masses in H 2O, D 2O, and D 2 18O, and CMP of hydrogenated and partially deuterated A8-35, a polyacrylate-based amphipol containing 35 underivatized carboxylates per 100 monomers, led to a consistent description of its buoyancy and charge properties.
ISSN:0003-2697
1096-0309
DOI:10.1016/j.ab.2004.07.033