  We present a theoretical analysis that associates the resonances of
extraordinary acoustic Raman (EAR) spectroscopy [Wheaton et al., Nat Photon 9,
68 (2015)] with the collective modes of proteins. The theory uses the
anisotropic elastic network model to find the protein acoustic modes, and
calculates Raman intensity by treating the protein as a polarizable ellipsoid.
Reasonable agreement is found between EAR spectra and our theory. Protein
acoustic modes have been extensively studied theoretically to assess the role
they play in protein function; this result suggests EAR as a new experimental
tool for studies of protein acoustic modes.
