At what wavelength does maximum nucleic acid absorption occur?

Nucleic acids, such as DNA and RNA, exhibit maximum absorption of ultraviolet (UV) light at a wavelength of 260 nm. This is primarily due to the presence of aromatic bases within their structure, particularly the nucleobases adenine, guanine, cytosine, and thymine or uracil, which absorb UV light effectively in this region.

At 260 nm, these bases can be excited by UV light, leading to photon absorption that facilitates techniques such as spectrophotometry for quantifying nucleic acids. This peak at 260 nm is a key wavelength used in molecular biology for assessing the concentration and purity of nucleic acids, as it allows researchers to measure the absorbance and extrapolate information regarding nucleic acid content in a sample.

Other wavelengths, such as 220 nm and 280 nm, are associated with the absorption characteristics of proteins and smaller molecules, with 280 nm being particularly relevant for assessing protein concentrations due to the presence of aromatic amino acids. The absorption values at these wavelengths do not represent the maximum for nucleic acids, underscoring the specificity of the 260 nm peak in this context.