Hydration of apomyoglobin in native, molten globule, and unfolded states by using microwave dielectric spectroscopy

Takashi Kamei, Motohisa Oobatake, Makoto Suzuki

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29 Citations (Scopus)

Abstract

The high resolution dielectric spectra of semidilute solutions of apomyoglobin in native (N, pH = 5), acidinduced molten globule (A, pH = 4), and unfolded (UA, pH = 3) states have been measured in the range from 0.2 to 20 GHz. Based on a two-component mixture theory, we obtained the following hydration numbers per protein molecule: 590 ± 65 for N, 630 ± 73 for A, and 1110 ± 67 for UA. There was no clear difference between N and A states in contrast to the 25% reduction of helix content and the 50% reduction of heat capacity change upon unfolding. This suggests that the association of hydrophobic moieties might follow the disruption of secondary structures from N to A states. The measured hydration number of UA was close to that of the accessible water number (1340) of a protein molecule calculated for a fully extended structure, indicating that the structure of UA is extended but somewhat more compact than that of a fully extended state.

Original languageEnglish
Pages (from-to)418-425
Number of pages8
JournalBiophysical Journal
Volume82
Issue number1
DOIs
Publication statusPublished - 2002 Jan 1

ASJC Scopus subject areas

  • Biophysics

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