Effects of lyotropic anions on thermodynamic stability and dynamics of horse cytochrome c.

This paper evaluates the effect of various lyotropic anions (chloride, sulfate, perchlorate, iodide, nitrate, bromide) on the thermodynamic stability and dynamics of native cytochrome c (Cyt c) at pH 7.0. The results of equilibrium and kinetic studies revealed that: (i) at low to intermediate concentrations (≤ 0.5 M), both chaotropic and kosmotropic anions restrict the dynamics of native protein, (ii) at relatively higher concentrations (≥ 1.0 M), the denaturing effect of chaotropic anions dominates, which increases the level of structural-fluctuations responsible to unfold the protein according to Hofmeister series (perchlorate > iodide > nitrate > bromide), and (iii) the lyotropic anions affect the thermal and global stability of Cyt c according to Hofmeister series. The m-value was determined from ΔΔG vs [Cosolute] plot and was found to be positive for sulfate and negative for other anions consistent with effect of lyotopic anions on protein stability according to Hofmeister series.