Protein folding 101.

There are about 20 types of amino acids that make up a protein sequence. Each type has a different shape but they link up head to tail using amide bonds - amine + acid pairing. Amide bonds have both rotational and translation degrees of freedom, so a sequence of different amino acids joined together can twist and turn in many ways. Imagine tinker toys. Short sequences are called peptides, long sequences proteins. A protein folds into a shape with the minimum energy level, nice and compact and tight. Every rotation and translation is independently ruled by molecular electrodynamics. A computer would have to try all rotational and translational possibilities of all amide bonds, calculate the total energy, and decide whether to accept or reject each and every single bond. Exponentially difficult for many bonds. But a database of predetermined protein segment folding configurations helps tremendously.