关键词: protein folding, sub-microsecond, laser-induced temperature-jump, transient infrared\linebreak \hbox{\hskip 1.9cm} spectrum, dynamics, cytochrome $C$

Abstract: Elucidating the initial kinetics of folding pathways is critical to the understanding of the protein folding mechanism. Transient infrared spectroscopy has proved a powerful tool to probe the folding kinetics. Herein we report the construction of a nanosecond laser-induced temperature-jump ($T$-jump) technique coupled to a nanosecond time-resolved transient mid-infrared (mid-IR) spectrometer system capable of investigating the protein folding kinetics with a temporal resolution of 50 ns after deconvolution of the instrumental response function. The mid-IR source is a liquid N$_{2}$ cooled CO laser covering a spectral range of 5.0$\mu$m (2000 cm$^{-1}) \sim $ 6.5$\mu$m (1540 cm$^{-1})$. The heating pulse was generated by a high pressure H$_{2}$ Raman shifter at wavelength of 1.9$\mu$m. The maximum temperature-jump could reach as high as 26$\pm $1$^{\circ}$C. The fast folding/unfolding dynamics of cytochrome $C$ was investigated by the constructed system, providing an example.

Key words: protein folding, sub-microsecond, laser-induced temperature-jump, transient infrared spectrum, dynamics, cytochrome $C$