Composition dependent multiple structural transformations of myoglobin in aqueous ethanol solution: a combined experimental and theoretical study

Ghosh, R. ; Samajdar, R. N. ; Bhattacharyya, Aninda Jiban ; Bagchi, B. (2015) Composition dependent multiple structural transformations of myoglobin in aqueous ethanol solution: a combined experimental and theoretical study The Journal of Chemical Physics, 143 (1). Article ID 015103. ISSN 0021-9606

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Official URL: http://aip.scitation.org/doi/abs/10.1063/1.4923003...

Related URL: http://dx.doi.org/10.1063/1.4923003

Abstract

Experimental studies (circular dichroism and ultra-violet (UV) absorption spectra) and large scale atomistic molecular dynamics simulations (accompanied by order parameter analyses) are combined to establish a number of remarkable (and unforeseen) structural transformations of protein myoglobin in aqueous ethanol mixture at various ethanol concentrations. The following results are particularly striking. (1) Two well-defined structural regimes, one at xEtOH ∼ 0.05 and the other at xEtOH ∼ 0.25, characterized by formation of distinct partially folded conformations and separated by a unique partially unfolded intermediate state at xEtOH ∼ 0.15, are identified. (2) Existence of non-monotonic composition dependence of (i) radius of gyration, (ii) long range contact order, (iii) residue specific solvent accessible surface area of tryptophan, and (iv) circular dichroism spectra and UV-absorption peaks are observed. Interestingly at xEtOH ∼ 0.15, time averaged value of the contact order parameter of the protein reaches a minimum, implying that this conformational state can be identified as a molten globule state. Multiple structural transformations well known in water-ethanol binary mixture appear to have considerably stronger effects on conformation and dynamics of the protein. We compare the present results with studies in water-dimethyl sulfoxide mixture where also distinct structural transformations are observed along with variation of co-solvent composition.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
ID Code:109198
Deposited On:22 Dec 2017 10:16
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