TY - JOUR
T1 - Hyperquenching and cold equilibration strategies for the study of liquid-liquid and protein folding transitions
AU - Angell, Charles
AU - Wang, Li Min
N1 - Funding Information:
This work was made possible by support of the NSF, Solid State Chemistry program, under Grant No. DMR-0082535. We are grateful to Wu Xu for synthesizing ethylammonium nitrate, to Barry Ninham for helpful suggestions concerning the repression of aggregation effects in denatured proteins, and to Pablo Debenedetti and Srikanth Sastry for helpful commentaries on the mansucript.
PY - 2003/9/1
Y1 - 2003/9/1
N2 - In this paper we consider the extension of the recent quantitative studies of hyperquenched glassformers to include (1) systems that exhibit first order liquid-liquid phase transitions, and (2) systems that contain molecules, which, during normal cooling, undergo internal structural changes above the glass temperature. The general aim of these studies is to trap-in a high enthalpy, high entropy, state of the system and then observe it evolving in time at low temperatures during a controlled annealing procedure. In this manner events that normally occur during change of temperature may be observed occurring during passage of time, at much lower temperatures. At such low temperatures the smearing effects of vibrations are greatly reduced. While the case of most interest in the second class is the refolding of thermally denatured protein molecules, any reconstructive molecular or chemical exchange process is a potential subject for investigation. Processes that occur in stages can be studied in greater detail, and any stage of interest can be frozen when desired, by drop of temperature, for more detailed spectroscopic examination. We review an electrospray method for hyperquenching liquids at approximately 10 5 K/s, and discuss some results of such experiments in order to illustrate a calorimetric approach to exploiting the hyperquenching-and- cold-equilibration strategy. To apply the idea to the study of proteins, the following protein solvent requirements must be met: (1) the solvents must not crystallize ice on cooling or heating, yet must not denature the proteins; (2) the solvents must support thermally denatured molecules without permitting aggregation. We describe two solvent systems, the first of which meets the first requirement, but the second only partially. The second solvent system apparently meets both. Preliminary results, only at the proof of concept stage, are reported for cold refolding of lysozyme, which, it seems, can be trapped in our solvent in the unfolded but refoldable state, with only moderate (approx. 120 K/s) quenching rates.
AB - In this paper we consider the extension of the recent quantitative studies of hyperquenched glassformers to include (1) systems that exhibit first order liquid-liquid phase transitions, and (2) systems that contain molecules, which, during normal cooling, undergo internal structural changes above the glass temperature. The general aim of these studies is to trap-in a high enthalpy, high entropy, state of the system and then observe it evolving in time at low temperatures during a controlled annealing procedure. In this manner events that normally occur during change of temperature may be observed occurring during passage of time, at much lower temperatures. At such low temperatures the smearing effects of vibrations are greatly reduced. While the case of most interest in the second class is the refolding of thermally denatured protein molecules, any reconstructive molecular or chemical exchange process is a potential subject for investigation. Processes that occur in stages can be studied in greater detail, and any stage of interest can be frozen when desired, by drop of temperature, for more detailed spectroscopic examination. We review an electrospray method for hyperquenching liquids at approximately 10 5 K/s, and discuss some results of such experiments in order to illustrate a calorimetric approach to exploiting the hyperquenching-and- cold-equilibration strategy. To apply the idea to the study of proteins, the following protein solvent requirements must be met: (1) the solvents must not crystallize ice on cooling or heating, yet must not denature the proteins; (2) the solvents must support thermally denatured molecules without permitting aggregation. We describe two solvent systems, the first of which meets the first requirement, but the second only partially. The second solvent system apparently meets both. Preliminary results, only at the proof of concept stage, are reported for cold refolding of lysozyme, which, it seems, can be trapped in our solvent in the unfolded but refoldable state, with only moderate (approx. 120 K/s) quenching rates.
KW - Aggregation
KW - Cold refolding
KW - Crystallization
KW - Energy landscape
KW - Fictive temperature
KW - Glass transition
KW - Hyperquench
KW - Liquid-liquid transition
KW - Protein folding
KW - Renaturation
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U2 - 10.1016/S0301-4622(03)00093-0
DO - 10.1016/S0301-4622(03)00093-0
M3 - Article
C2 - 14499923
AN - SCOPUS:0141453955
SN - 0301-4622
VL - 105
SP - 621
EP - 637
JO - Biophysical Chemistry
JF - Biophysical Chemistry
IS - 2-3
ER -