Fig 1.
LiBr-induced denaturation of cyt-c at pH 6.0 and 25°C.
Equilibrium unfolding transition curves are monitored by Δε400 (A) and Δ[θ]409 (B). Panels (C) and (D) show the normalized transition curves and plots of ΔGI and ΔGII as function of [LiBr], respectively. The inset in panel (B) shows the plot for the dependence of the optical property of X state (yX) on [LiBr] on the expanded scale. Filled symbol in panel (D) represents ΔGI (or ΔGII) determined from heat-induced denaturation in the presence of a given [LiBr].
Table 1.
Thermodynamic parameters characterizing the weak salt denaturants-induced denaturations of cyt-c at pH 6.0 and 25 ± 0°C.
Fig 2.
Equilibrium denaturation curves of cyt-c in the presence of LiCl (Ο) and LiClO4 (Δ) at pH 6.0 and 25°C.
Denaturation was monitored by Δε400 (A), Δ[θ]409 (B) and [θ]222 (C). Inset in panel (B) shows the plot for the dependence of the optical property of the X state (yX) on [denaturant] on the expanded scale. Panel (D) shows plots of ΔGI and ΔGII versus [denaturant]. In this panel filled symbols are obtained from the studies of thermal denaturation in the presence of weak salt denaturants.
Fig 3.
Structural characterization of various states of cyt-c.
In this figure curve numbers have the same meaning in all panels: 1, native state; 2, LiCl-induced MG state in the presence of 6.2 M concentration; 3, LiClO4-induced MG state in the presence of 1.9 M concentration; 4, LiBr-induced MG state in the presence of 4.2 M concentration; 5, 0.5 M NaCl-induced at pH 2.0; and 6, GdmCl-induced denatured state. Panels A and C show the far-UV and near-UV CD spectra. Panel B shows FTIR spectra. Panels D and E show ANS and Trp-fluorescence spectra. Panel F shows near-IR spectra.
Table 2.
Structural and thermodynamic properties of various molten globule (MG) states of cyt-c at 25°C and pH 6.0.
Fig 4.
Thermal denaturation of cyt-c in the presence of different LiBr concentrations measured by Δε400 at pH 6.0.
Panels A and C represent N↔X transition, and panels B and D represent X↔D transition. All curves are not shown to maintain clarity. Inset in panel (A) shows plots of yx, the optical property of X state on temperature at different LiBr concentrations. Plots of ΔHm versus Tm of cyt-c in the presence of LiCl (Ο), LiClO4 (□) and LiBr (Δ) obtained from Δε400 measurements for N↔X process (C), while panel (D) shows (ΔHm, Tm) data for the process X↔D. Filled symbol represents data point obtained from [θ]222 measurements.
Table 3.
Comparison of thermodynamic parameters of cyt-c in the presence of different denaturants at pH 6.0 and 25oCa,.