Circular dichroism (CD), which is the differential absorbance between left- and right-handed circularly polarized light, is a very popular technique for analyzing the secondary structure of biomolecules at equilibrium in solution. Combination of pump-probe techniques and CD spectroscopy provides a versatile tool to access the conformational and electronic structure changes of biological molecules over a wide range of time scales.
Despite recent technological advances, time-resolved CD experiments at the femto-picosecond time scale remain challenging, due to their very weak signals prone to artifacts [1]. In recent years, we have designed several setups to measure the light-induced CD changes of various chiral compounds over a time window ranging from a few hundred femtoseconds to a few seconds [2,3].
In this presentation, I will discuss the principle, advantages and drawbacks of these setups. I will illustrate their applications for studying the photoinduced conformational changes of proteins and short G-quadruplex DNA structures [4,5].