Dynamics of loop 1 of domain I in human serum albumin when dissolved in ionic liquids.

We report on the rotational reorientation dynamics associated with loop 1 of domain I within a large multidomain protein (human serum albumin, HSA) when it is dissolved in binary mixtures of ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), or 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6])) and distilled deionized water (ddH2O) as a function of temperature and water loading. In IL/2% ddH2O (v/v) mixtures, loop 1 of domain I is more significantly denatured in comparison to the protein dissolved in aqueous solutions containing strong chemical denaturants (e.g.