Figure 5. The potential energy diagrams for (a) sucrose and (b) arginine.

(a) For sucrose, two conformations of the unfolded state (U and U′) were found present in equilibrium. U is extended and U′ is relatively more compact and energetically unfavorable. The addition of sucrose enhanced the population of U′ resulting in higher free energy of unfolding (ΔG_Suc,C ≫ ΔG). ΔG and ΔG_Suc,C are the free energy of unfolding in the absence and presence of sucrose at concentration C, respectively. The folding pathways in the absence and presence of sucrose were differentiated using blue solid line (in the absence) and red dotted line (in the presence of sucrose), respectively. (b) The addition of arginine increases the free energy of the native states (and form N′). In the absence of arginine, refolding is complex and characterized by several pathways (stopped flow data, Figure 4g). The addition of arginine simplifies refolding and makes it relatively simpler (stopped flow data, Figure 4g) and more efficient (RE data, Figure 4e). The free energy diagrams in the absence and presence of the additives have been differentiated using blue solid line (in the absence) and red dotted line (in the presence of additives).