Rapid photochemical triggering of protein unfolding in a nondenaturing environment

A general, rapid method for triggering protein unfolding is demonstrated using the photolabile protecting group 3',5'-dimethoxybenzoin (DMB). This protecting group is introduced in a site-specific manner to block a mutation known to destabilize the GCN4-p1 coiled-coil. Upon photolysis, the unfavorable interaction is unmasked and the peptide unfolds, as seen in the decrease in α-helical ellipticity. Photothermal beam deflection and photoacoustic calorimetry reveal kinetic processes and associated volume changes with rates of 2 x 105-3 x 106 s-1, demonstrating that this photochemical technique is capable of triggering rapid protein conformational changes. Furthermore, this system allows conformational triggering under native solvent conditions, in the absence of chemical denaturants. The application of this strategy to following the early kinetics events in protein folding is discussed