Thermal denaturation of CP43 studied by Fourier transform-infrared spectroscopy and terahertz time-domain spectroscopy

Thermal denaturation of CP43 was studied by Fourier transform-infrared (FT-IR) spectroscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and terahertz time-domain spectroscopy (THz-TDS). Under heat treatment, the secondary structure of CP43 changed, and the main thermal transition occurred at 59 °C. During the process, CP43 aggregated at first, and then with increasing temperature degraded. The low-frequency collective vibrational modes of CP43 changed with increasing temperature and decreasing mass. THz-TDS is a new technique used to study the conformational state of a molecule, and it is the first use of this technique to study the photosynthesis membrane proteins in this paper. The results presented here demonstrate that THz-TDS has both advantages and disadvantages in monitoring the thermal denaturation of membrane proteins, which is important in applying THz-TDS technique to study of biomolecules.