Deep UV resonance Raman spectroscopy of β-sheet amyloid fibrils: a QM/MM simulation.

We present a combined quantum mechanics and molecular mechanics study of the deep ultraviolet ππ* resonance Raman spectra of β-sheet amyloid fibrils Aβ(34-42) and Aβ(1-40). Effects of conformational fluctuations are described using a Ramachandran angle map, thus avoiding repeated ab initio calculations. Experimentally observed effects of hydrogen-deuterium exchange are reproduced. We propose that the AmIII band redshift upon deuteration is caused by the loss of coupling between C(α)-H bending and N-D bending modes, rather than by peptide bond hydration.