Longer oligopeptides primary, secondary and tertiary structure

6 Longer oligopeptides primary, secondary and tertiary structure 

As the chain length increases further, other factors come into play to determine the overall conformation of the peptide and the electrically charged groups at the ends of the chain are less important in this respect. Interactions, repulsive and attractive, between side-chains are dominant and the primary structure (the sequence of the peptide and the stereochemistry at each chiral centre) determines the run of the peptide chain through the molecule (the secondary structure) and the overall shape of a single polypeptide chain (globular, extended, etc. the tertiary structure) of the molecule. 

The term domain is applied to describe regions within a protein molecule. Particular associations can arise between distinct secondary structures within the tertiary structure (an a-helix in one part of the polypeptide molecule can pack with a particular region elsewhere in the sequence a (3-sheet can be stabilised by a nearby structural feature from a distinct part of the polypeptide sequence). These domains 

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