Spectrographic representation of globular protein breathing motions.

Two useful ways of describing the frequency composition of the breathing motions of globular proteins are the spectrogram and three-dimensional power spectrum, representations similar to those frequently used in speech analysis. In this report "low-frequency" vibrations of globular proteins, corresponding to the collective oscillations of atoms from many different residues, are considered. Radii of gyration fluctuations provide a sensitive way to characterize such concerted motions.