Development of time-resolved and high sensitive circular dichroism spectroscopy aiming to detection of the structural change dynamics of biomolecules

Abstract

Time-resolved circular dichroism (CD) spectroscopy selectively gives us the dynamics information of molecule being in chiral circumstance. Here, we introduce the new type of CD detection method by using the elliptically polarized light instead of circular polarized one. The CD signal enhancement depending on the retarder orientation was observed in our strategy, resulting that the highly sensitive CD detection was achieved. On the basis of this technique, we have successfully constructed the time-resolved CD apparatus combined our CD setup with nanosecond laser system. Photo-irradiation of tetracationic porphyrin, H₂TMPyP as an achiral guest bound to the double strand DNA, showed mono-exponential CD dynamics in time-resolved CD experiments, which is consistent with the lifetime of photo-excited triplet state of H₂TMPyP revealed by the transient absorption spectroscopy. These results revealed that the time-resolved CD system is a useful tool to analyze kinetics and interaction dynamics of guest molecules to the chiral molecule such as bio-molecules.