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Nonmonotonic Hydration Behavior of Bovine Serum Albumin in Alcohol/Water Binary Mixtures: A Terahertz Spectroscopic Investigation
Author(s) -
Das Dipak Kumar,
Das Mahanta Debasish,
Mitra Rajib Kumar
Publication year - 2017
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201601217
Subject(s) - bovine serum albumin , chemistry , random coil , circular dichroism , alcohol , ethanol , spectroscopy , absorption (acoustics) , analytical chemistry (journal) , crystallography , chromatography , organic chemistry , materials science , quantum mechanics , composite material , physics
We report the experimental observation of nonmonotonic changes in the collective hydration of bovine serum albumin (BSA) in the presence of alcohols of varying carbon‐chain lengths, that is, ethanol, 2‐propanol, and tert ‐butyl alcohol (TBA), by using terahertz (THz) time domain spectroscopy. We measured the THz absorption coefficient ( α ) of the protein solutions, and it was observed that α fluctuated periodically as a function of alcohol concentration at a fixed protein concentration. For a fixed alcohol concentration, an increase in the protein concentration resulted in nonmonotonic changes in α ; thus, it first decreased rapidly and then increased, which was followed by a shallow decrease. An alcohol‐induced α helix to random coil transition of the protein secondary structure was revealed by circular dichroism spectroscopy measurements, and the effect was most prominent in TBA. The anomalous change in the hydration was found to be a delicate balance between the various interactions present in the three‐component system.