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

Journal Article · Tue Jul 07 00:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4923003· OSTI ID:22490877

Ghosh, R.; Samajdar, R. N.; Bhattacharyya, Aninda Jiban

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 x{sub EtOH} ∼ 0.05 and the other at x{sub EtOH} ∼ 0.25, characterized by formation of distinct partially folded conformations and separated by a unique partially unfolded intermediate state at x{sub EtOH} ∼ 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 x{sub EtOH} ∼ 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.

• OSTI ID: 22490877
• Journal Information: Journal of Chemical Physics, Vol. 143, Issue 1; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ABSORPTION SPECTRA
BINARY MIXTURES
COMPARATIVE EVALUATIONS
CONCENTRATION RATIO
DICHROISM
DMSO
ETHANOL
INTERMEDIATE STATE
MOLECULAR DYNAMICS METHOD
MYOGLOBIN
ORDER PARAMETERS
PEAKS
SIMULATION
SOLUTIONS
SOLVENTS
SURFACE AREA
TRYPTOPHAN
WATER