Electronic Circular Dichroism Spectroscopy of Proteins

Abstract

Electronic circular dichroism (CD) spectroscopy is an important tool for the elucidation of biomolecular structure. This review describes the latest progress and developments in experimental and theoretical studies of proteins using CD spectroscopy, including time-resolved measurements, oriented CD, and stateof-the-art experiments using polarized UV light from high-energy synchrotron radiation. Statistical and machine learning methods for the analysis of experimental spectra are surveyed. Computational methods employed to predict CD spectra from structure include ab initio quantum chemistry techniques, time-dependent density functional theory, and exciton theory. We describe recent computations using exciton theory, where we outline the importance of electronic-vibrational coupling and the influence of electrostatics of the protein environment on the electronic transitions in the chromophores responsible for CD signals in the near UV. Improvements in the accuracy of the computational approaches should allow more quantitative studies, applying a combination of experimental data and modeling to a variety of interesting questions. Fundamentals of the Phenomenon of Electronic Circular DichroismCircular dichroism (CD) is the differential absorption of left-and right-handed circularly polarized light. An elliptically polarized light wave results when a linearly polarized light wave passes through an optically active chiral compound. The magnitude of the effect is given by

Computed optical spectra of SARS-CoV-2 proteins

“…In the exciton framework an effective Hamiltonian is constructed from a basis of local excitations [33] . The exciton methodology for protein CD calculations has been recently reviewed [34] . The electronic transitions of the aromatic side chain chromophores, phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp), were described via ab initio calculated parameters [35] extended to incorporate the vibrational structure under the electronic bands [36] .…”

Near-Ultraviolet Circular Dichroism and Two-Dimensional Spectroscopy of Polypeptides

“…Jasim et al [ 19 ] have studied the near-UV CD spectra of BPTI in detail, where the influence of the electrostatic environment of the protein on the CD spectra has also been considered [ 32 ]. The computed and the experimental [ 17 ] spectra are shown in Figure 4 .…”

“…Recently, we have incorporated the vibrational structure of aromatic electronic excitations into exciton calculations of the near-UV CD spectra of proteins [ 18 , 19 , 32 ]. The approach and associated parameters build on earlier ab initio parameters [ 33 ] that have been assessed on a range of proteins and give good agreement between the computed and experimental near-UV CD spectra.…”

The Secondary Structure of a Major Wine Protein is Modified upon Interaction with Polyphenols

“…CD spectroscopy is a well-known technique for studying protein folding and secondary structure. Moreover, its high sensitivity to sample perturbation allows for investigating protein structures as a function of temperature, solvent composition, chemical agents and ligand interactions [38]. The high photon flux and brilliance of the synchrotron radiation used in SRCD spectroscopy allows for obtaining a high signal to noise ratio when compared to bench-top instruments.…”