Time resolved transient circular dichroism spectroscopy using synchrotron natural polarization

Abstract

Ultraviolet (UV) synchrotron radiation circular dichroism (SRCD) spectroscopy has made an important contribution to the determination and understanding of the structure of bio-molecules. In this paper, we report an innovative approach that we term time-resolved SRCD (tr-SRCD), which overcomes the limitations of current broadband UV SRCD setups. This technique allows accessing ultrafast time scales (down to nanoseconds), previously measurable only by other methods, such as infrared (IR), nuclear magnetic resonance (NMR), fluorescence and absorbance spectroscopies, and small angle X-ray scattering (SAXS). The tr-SRCD setup takes advantage of the natural polarization of the synchrotron radiation emitted by a bending magnet to record broadband UV CD faster than any current SRCD setup, improving the acquisition speed from 10 mHz to 130 Hz and the accessible temporal resolution by several orders of magnitude. We illustrate the new approach by following the isomer concentration changes of an azopeptide after a photoisomerization. This breakthrough in SRCD spectroscopy opens up a wide range of potential applications to the detailed characterization of biological processes, such as protein folding and protein-ligand binding.

On the Transition from a Biomimetic Molecular Switch to a Rotary Molecular Motor

“…Such measurements represent a timely target as, in recent years, ECD has been implemented in pumpprobe experiments allowing to track the variations of UV-vis circular dichroism signals on the subpicosecond time-scale. [22][23][24] In addition, pump-probe vibrational circular dichroism (VCD) has been developed in the mid-IR spectral range to monitor the structural changes on the picosecond timescale. 25,26 Over the past 10 years, we have been involved in the design, synthesis and characterization of lightdriven molecular switches (LDMSs), i.e.…”

Unfolding Dynamics of a Photoswitchable Helical Peptide

“…In the literature, the stable conformation of the cis-FK-11-X peptide has been associated with the conformation at 120 ns in Figure 6. 39 The experimental synchrotron radiation CD (SRCD) spectra of the trans and the cis configuration of FK-11-X have the same shape but with different amplitudes 65 (Figure 11b). Thus, the stable conformation of the cis-FK-11-X is partially helical.…”

Roadmap on dynamics of molecules and clusters in the gas phase

“…As for the investigation of chirality, the use of multicoincidence technique, where up to five correlated fragment ions have been detected simultaneously [42], may pave the way to the determination of absolute configuration on the single-molecule level in the gas phase. Moreover, the recently introduced time resolved transient circular dichroism in the VUV region, which exploits the synchrotron natural polarization, allows to access timescales down to ns like in the isomer concentration changes during/after photo-isomerization [43].…”