The use of second derivative plots for the determination of mol% guanine plus cytosine of DNA by the thermal denaturation method

Abstract

Procedures for the estimation of thermal denaturation temperatures for the determination of the mol% G+C base composition of bacterial DNA have been examined with a view to simplifying the procedure and taking advantage of developments in microprocessor controlled spectrophotometers. Thermal denaturation profiles of DNA from 40 strains with base compositions ranging from 35 to 70 mol% G+C were studied. Thermal denaturation temperatures were determined by the conventional Tm method and by using second derivative plots to determine the temperature of inflection (Ti). The results showed that there is a close linear correlation between mol% G+C values calculated using Tm or Ti as the thermal den..