Advances in Synchrotron Radiation-Based Vacuum-Ultraviolet Circular Dichroism for Biomolecular Structural Analysis.

Vacuum-ultraviolet circular dichroism (VUVCD) spectroscopy using synchrotron radiation is a powerful tool for characterizing the structures of biomolecules in aqueous solutions. When combined with bioinformatics, VUVCD enables detailed determination of protein secondary-structure contents, segment numbers, and sequence distributions, while coupling with linear dichroism and shear flow techniques provides insights into the orientations of secondary structures. These analytical approaches have been applied to the structural characterization of membrane-bound α-synuclein (αS), a protein which transforms into amyloid fibrils associated with Parkinson's disease, successfully revealing the molecular mechanism of αS fibril-formation on membranes. Furthermore, time-resolved measurements using microfluidic device allow direct observation of protein structural dynamics during membrane interactions. The combination of VUVCD spectroscopy with molecular dynamics simulations in aqueous environments has also been applied to determine the absolute configurations of saccharides containing higher-energy chromophores, thereby elucidating hydration structures involving intra- and intermolecular hydrogen bonds. Recent studies have further expanded these applications to monitor the conformational changes of extracellular polysaccharides and polyhydroxyalkanoates as functions of temperature and membrane interactions. These advancements highlight that integrating VUVCD spectroscopy with computational and other experimental approaches can significantly enhance the structural characterization of diverse biomolecules at molecular level.