Cosolvent-induced adsorption and desorption of serum proteins on an amphiphilic mercaptomethylene pyridine-derivatized agarose gel

We studied the effects of the following cosolvents on the adsorption and desorption of serum proteins from an amphiphilic mercaptomethylene pyridine-derivatized agarose gel: glucose, sucrose, polyethylene glycol (PEG), 2-methyl-2,4-pentanediol (MPD), sorbitol, pentaerythritol, glycerol, and Na2SO4. The water-structuring salt 0.4 M Na2SO4 was the most potent promoter of protein adsorption, followed by 5 M sorbitol and, to a lesser extent, 0.2 M PEG 1000 and 2.25 M MPD. The other cosolvents (4 M glucose, 1.5 M sucrose, 0.3 M pentaerythritol, and 7.6 M glycerol) were unable to promote protein adsorption to the gel. Attempts to modulate the salt-promotion effect of Na2SO4 with different cosolvents demonstrated the occurrence of synergistic effects for pentaerythritol, sorbitol, and glucose and antagonistic effects for the other cosolvents. Sorbitol and glycerol were found to be the most interesting cosolvents studied, as the first promoted protein adsorption, whereas the other disrupted protein interaction. As a consequence of these novel findings we propose sorbitol and glycerol, both well-known protein stabilizers, as possible alternatives to water-structuring salts during the adsorption phase and to deleterious organic solvents during the desorption phase on amphiphilic gels. (C) 1996 Academic Press, Inc.