3. Protein folding kinetics investigated by nanosecond time-resolved mid-IR spectroscopy.
Proteins are constructed by a polypeptide chains folded in a unique form known as native structure to carry out their biological function. The fundamental question of protein folding is how a polypeptide chain of astronomically possible conformations finds its unique native biologically active structure in a finite time. Various methods have been developed to explore the mechanism of protein folding. The temporal resolution depends on not only the way how protein folding is triggered, but also how the structural change is probed. We have constructed a liquid nitrogen cooled CO IR laser, with a tunable output frequency from about 2000 to 1540 cm-1 covering the whole spectral range of amide I band. We have demonstrated it is an excellent probe source for T-jump time-resolved IR spectroscopic study of protein folding for cytochrome c and other proteins.
Cytochrome c structure and the schematic diagram showing T-jump induced unfolding of loop containing Met80 bound to the heme Fe(III).