TY - JOUR
T1 - Specific ion effects on the water solubility of macromolecules
T2 - PNIPAM and the Hofmeister series
AU - Zhang, Yanjie
AU - Furyk, Steven
AU - Bergbreiter, David E.
AU - Cremer, Paul S.
PY - 2005/10/19
Y1 - 2005/10/19
N2 - Aqueous processes ranging from protein folding and enzyme turnover to colloidal ordering and macromolecular precipitation are sensitive to the nature and concentration of the ions present in solution. Herein, the effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated with a temperature gradient microfluidic device under a dark-field microscope. While the ability of a particular anion to lower the LCST generally followed the Hofmeister series, analysis of solvent isotope effects and of the changes in LCST with ion concentration and identity showed multiple mechanisms were at work. In solutions containing sufficient concentrations of strongly hydrated anions, the phase transition of PNIPAM was directly correlated with the hydration entropy of the anion. On the other hand, weakly hydrated anions were salted-out through surface tension effects and displayed improved hydration by direct ion binding.
AB - Aqueous processes ranging from protein folding and enzyme turnover to colloidal ordering and macromolecular precipitation are sensitive to the nature and concentration of the ions present in solution. Herein, the effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated with a temperature gradient microfluidic device under a dark-field microscope. While the ability of a particular anion to lower the LCST generally followed the Hofmeister series, analysis of solvent isotope effects and of the changes in LCST with ion concentration and identity showed multiple mechanisms were at work. In solutions containing sufficient concentrations of strongly hydrated anions, the phase transition of PNIPAM was directly correlated with the hydration entropy of the anion. On the other hand, weakly hydrated anions were salted-out through surface tension effects and displayed improved hydration by direct ion binding.
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U2 - 10.1021/ja0546424
DO - 10.1021/ja0546424
M3 - Article
C2 - 16218647
AN - SCOPUS:26844452263
SN - 0002-7863
VL - 127
SP - 14505
EP - 14510
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 41
ER -