  Alignment of molecules through electric fields minimizes the averaging over
orientations, e. g., in single particle imaging experiments. The response of
molecules to external ac electric fields is governed by their polarizability
tensor, which is usually calculated using quantum-chemistry methods. These
methods are not feasible for large molecules. Here, we calculate the
polarizability tensor of proteins using a regression model that correlates the
polarizabilities of the 20 amino acids with perfect conductors of the same
shape. The dielectric constant of the molecules could be estimated from the
slope of the regression line based on Clausius Mossotti equation. We benchmark
our predictions against the quantum chemistry results for the Trp cage mini
protein and the measured dielectric constants of larger proteins. Our method
has applications in computing laser-alignment of macromolecules, for instance,
benefiting single particle imaging, as well as for the estimation of the
optical and electrostatic characteristics of proteins and other macromolecules.

Chemical Physics