Theoretical Raman optical activity study of the beta domain of rat metallothionein.

We present the calculated vibrational Raman optical activity (ROA) spectrum of the beta domain of rat metallothionein, which is the by far largest molecule for which full ab initio ROA calculations have been performed up to date with more than 400 atoms. While ROA signatures of regular secondary structure elements like beta-sheets and alpha-helices can be conveniently studied in terms of small model structures, this is no longer possible for more irregular proteins like metallothionein. The only secondary structure elements occurring in the molecule are turns, in particular beta turns. Our calculations reveal that especially bands in the wavenumber range from about 1100 to 1400 cm(-1) may be employed as signatures of such beta turns. This is also found in comparison to experimental data. In addition, good agreement between calculated and experimental spectra is found.