Abstract
In this work, time dependent density functional theory (TD-DFT) is used to provide a reliable basis for interpretation of the electronic spectra of coupled tryptophan (Trp) residues, particularly those in a model Trpzip beta-hairpin peptide. Pairs of isolated indoles form chiral coupled chromophores whose computed electronic ultraviolet circular dichroism (CD) is in excellent agreement with observed transition wavelengths and intensities. The calculations were compared to experimental data for pairwise coupling in mutant Trpzip peptides that are recently available. A study of variation of the basis set, geometry optimization, and the solvent environment on the spectra showed limited impact on bandshapes. An alternative simplified computational scheme, dependent on the transition dipole coupling (TDC) mechanism, is shown to give a representation of qualitative aspects of the intense CD for the (1)B bands at 228 and 213 nm. The results confirm the origin of the Trpzip diagnostic CD as primarily a dipolar interaction between Trp sidechains, and show that quantum computations of electronic CD can provide a reliable basis for interpretation of these chirally coupled aromatic spectral phenomena.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.