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

doi:10.1016/0167-7012(86)90009-6

Journal of Microbiological Methods

Volume 5, Issues 3–4, August 1986, Pages 139-156

https://doi.org/10.1016/0167-7012(86)90009-6 Get rights and content

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 T_m method and by using second derivative plots to determine the temperature of inflection (T_i). The results showed that there is a close linear correlation between mol% G+C values calculated using T_m or T_i as the thermal denaturation temperature, provided the thermal denaturation temperature of the internal reference DNA is estimated in the same way. Actual T_i values were approximately 0.3°C higher than corresponding T_m values but the increase was consistent across the range of DNA samples studied. The results also showed that the error introduced by disregarding correction for the effect of thermal expansion was not consistent across the range of DNA samples studied. However, the error was small and in practical terms could be neglected.

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^∗∗: Present address: Soils and Fertilizer Institute, Chinese Academy of Agricultural Sciences, Beijing, Peoples Republic of China.

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

Abstract

J. Mol. Biol.

J. Mol. Biol.

Re-examination of the association between melting point, buoyant density and chemical base composition of deoxyribonucleic acid

J. Bacteriol.

Genetic characterization

Étude comparative des methodes de détermination du Tm de L'ADN bactérien

Ann. Microbiol. (Inst. Pasteur)

A procedure for the isolation of deoxyribonucleic acid from micro-organisms

J. Mol. Biol.

Purification of mycobacterial deoxyribonucleic acid

J. Bacteriol.

Étude comparative des methodes de détermination du T_m de L'ADN bactérien