Estimation of secondary/tertiary structure.

A protein has three types of structure: primary, its covalent sequence; secondary, the local arrangement of the polypeptide chain; tertiary, the mutual three-dimensional arrangement of the chain. Two spectroscopic techniques allow convenient estimation of the amount and type of secondary structure in a pure protein. Analysis of the Fourier Transform Infra Red Spectrum of the Amide I band of a protein (1650 cm(-1)) allows direct evaluation of the relative amounts of the peptide groups in various secondary structures. The Circular Dichroism Spectrum of the peptide chromophore (below 240 nm) can yield similar information and may allow assignment of the protein in one of five general structural classes.