TeraChem is a recently introduced electronic structure package that uses GPU parallelism to compute the ground and excited states of molecules of unprecedented size. The code is thus a natural choice for QM and QM/MM molecular dynamics simulations. We describe the interface of the TeraChem and AMBER codes and apply this QM/MM molecular dynamics technique to TDDFT computation of the absorption spectra of photoactive yellow protein (PYP) in a variety of environments. We explore the effects of long-range electrostatics by computing the spectra for various QM regions and MM cutoff values.  Comparisons are made to spectra of the PYP chromophore in vacuum and in aqueous solution, in which the waters are treated with both MM and QM methods.

Ab initio QM/MM molecular dynamics using TeraChem and AMBER:  Exploring environmental effects on the absorption spectrum of photoactive yellow protein

244th National Meeting (2012)

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