Graphical analysis of circular dichroic spectra distinguishes between two-state and gradual alterations in DNA conformation.

A simple graphical method is proposed to distinguish between two-state and gradual alterations in DNA conformation from circular dichroic spectra. The method is advantageous particularly to identify two-state conformational isomerizations which exhibit low degree of cooperativity. The usefulness of the method is illustrated on the examples of two synthetic DNA molecules which isomerize due to temperature changes or changes in salt concentration. The method can be used to characterize any phenomenon accompanied by alterations in optical activity.