Folding of bovine β-lactoglobulin in a ternary solvent system at subzero temperatures evaluated using the stopped-flow technique coupled with circular dichroism and intrinsic fluorescence

Abstract

The folding of β-lactoglobulin was monitored according to the stopped-flow technique coupled with circular dichroism and fluorescence at –30℃ in the presence of a ternary solvent system (ethylene glycol 25% - methanol 20% - buffer 55%). We observed three phases, as noted in the binary solvent system (ethylene glycol 45% - buffer 55%) (Qin et al., 2001, FEBS lett., 507, 299-302). The fastest phase within the dead time of the stopped-flow apparatus (10 ms) and the second phase (3.8 s at –30℃) resulted in an increased α-helix content. The ternary solvent system is advantageous due to its lower viscosity. However, the results should be critically examined, as this system is more favorable for α-helix formation.