Nucleic Acids: Thermal Stability and Denaturation


Nucleic acid structures can have different stabilities that depend on a variety of factors that include the nucleic acid sequence, the structure adopted, and the solution environment. Together, these factors influence the thermal stability of the complex.

Keywords: DNA melting; RNA melting; duplex stability; base pairing

Figure 1.

An example of an optical melting curve for a short DNA duplex. The absorbance at 268 nm was monitored as the temperature of the sample was raised from 2ºC to 70ºC. The resultant trace shows a sigmoidal transition. The midpoint of the transition is labelled and is referred to as the melting temperature or Tm.

Figure 2.

The hydrogen‐bonded structures of an A•T and a G•C base pair are shown. The aromatic bases lie in the same plane and are viewed from the perspective of looking down the axis of the double helix. Two hydrogen bonds are formed between the adenine and thymine bases, whereas three hydrogen bonds are formed between the guanine and cytosine bases. The R‐groups indicate the position of attachment to the sugar phosphate backbone.

Figure 3.

Examples of sugar phosphate backbones used in RNA, DNA and several structural variants that are described in the text.

Figure 4.

Nucleoside structures that exhibit degenerate base pairing properties. Structures shown are deoxyribose sugars attached to the bases (a) inosine, (b) 3‐nitropyrrole and (c) 5‐nitroindole.

Figure 5.

Examples of the various loop structures described in the text, including the eight different types of RNA mismatched base pairs, a symmetrical internal loop, a single‐base bulge loop, and a four‐base end loop.

Figure 6.

The hydrogen‐bonded structures involved in triplex and G‐quadruplex structures.



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Wetmur JG (1991) DNA probes: applications of the principles of nucleic acid hybridization. Critical Reviews in Biochemistry and Molecular Biology 26(3/4): 227–259.

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Doktycz, Mitchel J(Oct 2002) Nucleic Acids: Thermal Stability and Denaturation. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0003123]