Charge-Transfer Transitions in the Vacuum-Ultraviolet of
Protein Circular Dichroism Spectra
Benjamin M. Bulheller
Andrew J. Miles
B. A. Wallace
Jonathan D. Hirst
10.1021/jp077462k.s002
https://acs.figshare.com/articles/journal_contribution/Charge_Transfer_Transitions_in_the_Vacuum_Ultraviolet_of_Protein_Circular_Dichroism_Spectra/2957632
Circular dichroism (CD) is widely used in the structural characterization and secondary structure determination
of proteins. The vacuum UV region (below 190 nm), where charge-transfer transitions have an influence on
the CD spectra, can be accessed using synchrotron radiation circular dichroism (SRCD) spectroscopy. Recently,
charge-transfer transitions in a conformationally diverse set of dipeptides have been characterized ab initio
using complete active space self-consistent field calculations, and the relevant charge distributions have been
parametrized for use in the matrix method for calculations of protein CD. Here, we present calculations of
the vacuum UV CD spectra of 71 proteins, for which experimental SRCD spectra and X-ray crystal structures
are available. The theoretical spectra are calculated considering charge-transfer and side chain transitions.
This significantly improves the agreement with experiment, raising the Spearman correlation coefficient between
the calculated and the experimental intensity at 175 nm from 0.12 to 0.79. The influence of the conformation
on charge-transfer transitions is analyzed in detail, showing that the <i>n</i> → π* charge-transfer transitions are
most important in α-helical proteins, whereas in β strand proteins the π → π* charge-transfer transition
along the chain in the amino- to carboxy-end direction is most dominant.
2008-02-14 00:00:00
field calculations
matrix method
CD spectra
Protein Circular Dichroism SpectraCircular dichroism
175 nm
Spearman correlation coefficient
vacuum UV CD spectra
β strand proteins
71 proteins
SRCD spectra
synchrotron radiation
charge distributions
vacuum UV region
protein CD
ab initio
structure determination
side chain transitions