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Fluorinated alcohol, the third group of cosolvents that stabilize the molten-globule state relative to a highly denatured state of cytochrome c

Published online by Cambridge University Press:  01 March 2000

TAKASHI KONNO
Affiliation:
Center for Brain Experiment, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
JUN IWASHITA
Affiliation:
Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
KUNIAKI NAGAYAMA
Affiliation:
Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
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Abstract

The effects of 1,1,1,3,3,3-hexafluoro-isopropanol (HFIP) on the conformation of cytochrome c (cyt c) at pH 1.9 were studied using a combination of spectroscopic and physical methods. Analysis varying the HFIP concentration showed that a compact denatured conformation (MHF) accumulates in a low concentration range of HFIP in the middle of structural transition from the highly unstructured acid-denatured state to the highly helical alcohol-denatured state of cyt c. This contrasts clearly with the effect of isopropanol (IP), in which no compact conformation accompanied with the transition. Analysis varying concentrations of HFIP and NaCl concurrently showed that the MHF state of cyt c is essentially identical to the salt-induced molten-globule (MG) state, and the MG state in the presence of salt was also stabilized by a low concentration of HFIP. Furthermore, 2,2,2-trifluoroethanol stabilized MHF similarly to HFIP, supporting the proposition that the specific effect observed for HFIP is caused by fluorination of alcohol. The mechanism stabilizing compact conformation by HFIP remains unclear, but is probably distinct from that of salts and polyols, which are also known to stabilize the MG-like state.

Type
Research Article
Copyright
© 2000 The Protein Society

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