Abstract: A method is provided for determining the packing conformation of amino acid side chains on a fixed peptide backbone. Using a steric interaction potential, the side chain atoms are rotated about carbon-carbon bonds such that the side chains preferably settle in a low energy packing conformation. Rotational moves are continued according to a simulated annealing procedure until a set of low energy conformations are identified. These conformations represent the structure of the actual peptide. The method may be employed to identify the packing configuration of mutant peptides.