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Trifluoroethanol-induced conformational transitions of proteins: Insights gained from the differences between α-lactalbumin and ribonuclease A

Published online by Cambridge University Press:  01 March 1999

KLAUS GAST
Affiliation:
Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, D-13122 Berlin, Germany
DIETRICH ZIRWER
Affiliation:
Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, D-13122 Berlin, Germany
MARLIES MÜLLER-FROHNE
Affiliation:
Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, D-13122 Berlin, Germany
GREGOR DAMASCHUN
Affiliation:
Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, D-13122 Berlin, Germany Institute of Biology, Humboldt University at Berlin, c/o MDC, Robert-Rössle-Str. 10, D-13122, Germany
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Abstract

The trifluoroethanol (TFE)-induced structural changes of two proteins widely used in folding experiments, bovine α-lactalbumin, and bovine pancreatic ribonuclease A, have been investigated. The experiments were performed using circular dichroism spectroscopy in the far- and near-UV region to monitor changes in the secondary and tertiary structures, respectively, and dynamic light scattering to measure the hydrodynamic dimensions and the intermolecular interactions of the proteins in different conformational states. Both proteins behave rather differently under the influence of TFE: α-lactalbumin exhibits a molten globule state at low TFE concentrations before it reaches the so-called TFE state, whereas ribonuclease A is directly transformed into the TFE state at TFE concentrations above 40% (v/v). The properties of the TFE-induced states are compared with those of equilibrium and kinetic intermediate states known from previous work to rationalize the use of TFE in yielding information about the folding of proteins. Additionally, we report on the properties of TFE/water and TFE/buffer mixtures derived from dynamic light scattering investigations under conditions used in our experiments.

Type
Research Article
Copyright
© 1999 The Protein Society

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