Random coil
In
biochemistry, a
protein or a segment of a protein that completely lacks
secondary structure is a
random coil. In random coil, the only fixed relationship between
amino acids is that between adjacent residues through the
peptide bond. As a result, random coil can be detected from the absence of the signals in a multidimensional
nuclear magnetic resonance experiment that depend on particular peptide-peptide interactions. Likewise in the images produced in
crystallography experiments, pieces of random coil appear simply as an absence of "electron density" or contrast. Random coil is also easily distinguished by
circular dichroism.
Denaturing reduces a protein entirely to random coil.
See also: protein folding, native state, molten globule