Fractal analysis of protein potential energy landscapes

The fractal properties of the total potential energy V as a function of tim e t are studied for a number of systems, including realistic models of prot eins (pancreatic polypeptide, bovine pancreatic trypsine inhibitor, and myo globin). The fractal dimension of-V(t), characterized by the exponent gamma , is almost independent of temperature, and increases with time, more slowl y the larger the protein. Perhaps the most striking observation of this stu dy is the apparent universality of the fractal dimension, which depends onl y weakly on the type of molecular system. We explain this behavior by assum ing that fractality is caused by a self-generated dynamical noise, a conseq uence of intermode coupling due to anharmonicity. Global topological featur es of the potential energy landscape are found to have little effect on the observed fractal behavior. [S1063-651X(99)11402-8].