<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2013) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2013) (Learn how and when to remove this template message) </Td> </Tr> <P> Protein tertiary structure is the three dimensional shape of a protein . The tertiary structure will have a single polypeptide chain "backbone" with one or more protein secondary structures, the protein domains . Amino acid side chains may interact and bond in a number of ways . The interactions and bonds of side chains within a particular protein determine its tertiary structure . The protein tertiary structure is defined by its atomic coordinates . These coordinates may refer either to a protein domain or to the entire tertiary structure . A number of tertiary structures may fold into a quaternary structure . </P> <P> The science of the tertiary structure of proteins has progressed from one of hypothesis to one of detailed definition . Although Emil Fischer had suggested proteins were made of polypeptide chains and amino acid side chains, it was Dorothy Maud Wrinch who incorporated geometry into the prediction of protein structures . Wrinch demonstrated this with the Cyclol model, the first prediction of the structure of a globular protein . Contemporary methods are able to determine, without prediction, tertiary structures to within 5 Å (0.5 nm) for small proteins (<120 residues) and, under favorable conditions, confident secondary structure predictions . </P>

What holds a protein in its tertiary structure