Hydrophobic forces between protein molecules in aqueous solutions of concentrated electrolyte.
Protein-protein interactions have been measured for a mutant (D101F) lysozyme and for native lysozyme in concentrated solutions of ammonium sulfate at pH 7 and sodium chloride at pH 4.5. In the mutant lysozyme, a surface aspartate residue has been replaced with a hydrophobic phenylalanine residue. The protein-protein interactions of D101F lysozyme are more attractive than those of native lysozyme for all conditions studied. The salt-induced attraction is correlated with a solvation potential of mean force given by the work required to desolvate the part of the protein surfaces that is buried by the protein-protein interaction. This work is proportional to the aqueous surface-tension increment of the salt and the fractional non-polar surface coverage of the protein. Experimental measurements of osmotic second virial coefficients validate a proposed potential of mean force that ascribes the salt-induced attraction between protein molecules to an enhancement of the hydrophobic attraction. This model provides a first approximation for predicting the protein-protein potential of mean force in concentrated aqueous electrolyte solutions; this potential is useful for determining solution conditions favorable for protein crystallization.
Curtis
R A
RA
Chemical Engineering Department, University of California, Berkeley and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Steinbrecher
C
C
Heinemann
M
M
Blanch
H W
HW
Prausnitz
J M
JM
D011232:Chemical Precipitation; D003460:Crystallization; D004573:Electrolytes; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046911:Macromolecular Substances; D008956:Models, Chemical; D009113:Muramidase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D009994:Osmolar Concentration; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification; D012492:Salts / Q000737:chemistry; D012995:Solubility; D012996:Solutions; D013816:Thermodynamics; D014867:Water
D004573:Electrolytes; D046911:Macromolecular Substances; D011506:Proteins; D012492:Salts; D012996:Solutions; D014867:Water; D009113:Muramidase