ABSTRACT
From a chemical point of view, proteins are by far the most structurally complex and functionally sophisticated molecules known. This is perhaps not surprising, once people realize that the structure and chemistry of each protein has been developed and fine-tuned over billions of years of evolutionary history. A protein molecule consists of a long unbranched chain of these amino acids, each linked to its neighbor through a covalent peptide bond. The folding of a protein chain is also determined by many different sets of weak noncovalent bonds that form between one part of the chain and another. These involve atoms in the polypeptide backbone, as well as atoms in the amino acid side chains. Most proteins have a particular three-dimensional structure which is determined by the order of the amino acids in its chain. Most proteins fold up into a single stable conformation. However, this conformation changes slightly when the protein interacts with other molecules in the cell.
