Properties of GNM mode spectrum. (a) The reciprocal of eigenvalue (1/λ) for the first 20 GNM mode is plotted to show the motion frequency; higher values are for slower modes with low frequencies, which are relevant to biological functions. (b) The degree of collectivity is shown for the first 20 GNM modes. Higher degrees of collectivity indicate high cooperativity engaging a large portion of the protein and functional relevance.