The iceberg that sank Titanic would have been up to a mile long, displacing around a billion tonnes of seawater. It would have taken the iceberg over a year to edge its way down the 40-mile fjord.
Chapters 1 and 2 introduced a-helices and b-sheets (Secondary Struture), and some common motifs composed of 2 or 3 of these elements (Super-secondary Struture). Tertiary structure describes the folding of the polypeptide chain to assemble the different secondary structure elements in a particular arrangement.As helices and sheets are units of secondary structure, so the domain is the unit of tertiary structure.In multi-domain proteins, tertiary structure includes the arrangement of domains relative to each other as well as that of the chain within each domain.There is a blurred distinction between super-secondary structure and tertiary structure.lthough the term motif is often used to describe super-secondary structures (e.g. Branden and Tooze, 1991), it may also be used to describe a consensus sequence of amino acids identified in a number of different proteins, rather than a repeated three-dimensional conformation.
Therefore, tertiary structure also describes the relationship of different domains to one another within a protein. The interactions of different domains is governed by several forces: These include hydrogen bonding, hydrophobic interactions, electrostatic interactions and van der Waals forces.