Spectrophotometric Analysis of Nucleic Acids

The ability to quantify nucleic acids accurately and rapidly is a prerequisite for many of the methods used in biochemistry and molecular biology. In the majority of situations this is carried out using spectrophotometry, which is nondestructive and allows the sample to be recovered for further analysis or manipulation. Spectrophotometry uses the fact that there is a relationship between the absorption of ultraviolet light by DNA/RNA and its concentration in a sample. The absorption maximum of DNA/RNA is approx 260 nm. This figure is an average of the absorption of the individual nucleotides that vary between 256 and 281 nm. In the case of RNA, the concentration of a sample containing RNA may be calculated from Eq. 1 , where as for DNA Eq. 2 is used: