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

Abstract 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 ΔΔ G 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.