Editing Random coil (section)

== Spectroscopy ==
A random-coil conformation can be detected using spectroscopic techniques. The arrangement of the planar amide bonds results in a distinctive signal in [[circular dichroism]]. The [[chemical shift]] of amino acids in a random-coil conformation is well known in [[Protein NMR|nuclear magnetic resonance]] (NMR). Deviations from these signatures often indicates the presence of some secondary structure, rather than complete random coil. Furthermore, there are signals in multidimensional NMR experiments that indicate that stable, non-local amino acid interactions are absent for polypeptides in a random-coil conformation. Likewise, in the images produced by [[X-ray crystallography|crystallography]] experiments, segments of random coil result simply in a reduction in "electron density" or contrast. A randomly coiled state for any polypeptide chain can be attained by [[denaturation (biochemistry)|denaturing]] the system. However, there is evidence that proteins are never truly random coils, even when denatured (Shortle & Ackerman).