A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. Our web-server DichroCalc (http://comp.chem.nottingham.ac.uk/dichrocalc) allows one to compute from first principles the electronic circular dichroism spectrum of a (modelled or experimental) protein structure or ensemble of structures. The regular, repeating, chiral nature of secondary structure elements leads to intense bands in the far-ultraviolet. The near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, realised through the consideration of the vibronic structure of the electronic transitions of aromatic side chains and the influence of the electrostatic environment on the electronic excitation energies. The improvements have been assessed over a set of diverse proteins and we illustrate them, using bovine pancreatic trypsin inhibitor, triosephosphate isomerase and ubiquitin.

Computing protein circular dichroism spectroscopy in the near-ultraviolet

251st National Meeting (2016)

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