TY - JOUR
T1 - Protein Unfolding, and the "Tuning In" of Reversible Intermediate States, in Protic Ionic Liquid Media
AU - Byrne, N.
AU - Angell, Charles
N1 - Funding Information:
This work has been supported by the National Science Foundation, Chemistry Division under the Collaborative Research in Chemistry program, Grant No. 040714. We acknowledge stimulating discussions with our CRC colleagues P.G. Debenedetti, P. Rossky, and H. E. Stanley. The four protic ILs used in preparing the solutions of this work were kindly provided by Jean-Philippe Belieres (see Ref. 33 ). The aprotic IL was prepared in earlier work by Wu Xu (see ref. 34 ). The DSC instrument was purchased with funds from the NSF CHE grant no. 0608581 (to J. L. Yarger).
PY - 2008/5/2
Y1 - 2008/5/2
N2 - Protic ionic liquids (PILs) are currently being shown to be as interesting and valuable to chemical manipulations as the well-known aprotic ionic liquids (APIL). PILs have the additional advantage that the proton activity (PA) can be adjusted by the choice of Bronsted base and Bronsted acid used in their formation. In the absence of solvent, the PA plays the role of pH in ordinary solutions. Previously, we have shown that solution of proteins in ionic-liquid-rich solutions conveys surprising stabilization against hydrolysis and aggregation, permitting multiple unfold/refold cycles without loss to aggregation. Here, we show that the denaturing temperatures of both hen egg white lysozyme and ribonuclease A are sensitive to the PA of the PIL as much as they are to pH in aqueous solutions. A maximum stability for more basic solutions is found, and the unfolding process is well described by the two-state (cooperative) model. Finally, we show that, by PA tuning, the PILs can select folding pathways featuring the postulated intermediates so that they are fully populated during the unfolding process. The intermediates are themselves capable of multiple unfold/refold cycles with little loss per cycle to aggregation process.
AB - Protic ionic liquids (PILs) are currently being shown to be as interesting and valuable to chemical manipulations as the well-known aprotic ionic liquids (APIL). PILs have the additional advantage that the proton activity (PA) can be adjusted by the choice of Bronsted base and Bronsted acid used in their formation. In the absence of solvent, the PA plays the role of pH in ordinary solutions. Previously, we have shown that solution of proteins in ionic-liquid-rich solutions conveys surprising stabilization against hydrolysis and aggregation, permitting multiple unfold/refold cycles without loss to aggregation. Here, we show that the denaturing temperatures of both hen egg white lysozyme and ribonuclease A are sensitive to the PA of the PIL as much as they are to pH in aqueous solutions. A maximum stability for more basic solutions is found, and the unfolding process is well described by the two-state (cooperative) model. Finally, we show that, by PA tuning, the PILs can select folding pathways featuring the postulated intermediates so that they are fully populated during the unfolding process. The intermediates are themselves capable of multiple unfold/refold cycles with little loss per cycle to aggregation process.
KW - effective pH
KW - intermediate folding states
KW - protein unfolding
KW - protic ionic liquids
KW - proton activity
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U2 - 10.1016/j.jmb.2008.02.050
DO - 10.1016/j.jmb.2008.02.050
M3 - Article
C2 - 18384810
AN - SCOPUS:42249087622
SN - 0022-2836
VL - 378
SP - 707
EP - 714
JO - Journal of molecular biology
JF - Journal of molecular biology
IS - 3
ER -