Calculate nucleic acid concentration from spectrophotometer A260 readings using the Beer-Lambert Law.
Reading Parameters
Concentration Result
25.00µg/mL
Calculated Concentration
Extinction Factor50µg/unit
Absorbance0.5AU
Concentration Curve
Overview
Determining the concentration of nucleic acids (DNA and RNA) is fundamental in molecular biology. This is calculated using the Beer-Lambert Law based on absorbance at 260 nm. The standard factors represent the concentration required to produce an A260 of 1.0 with a 1 cm pathlength.
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Pro Tips
dsDNA conversion factor: 50 µg/mL per 1.0 A260 unit.
ssDNA conversion factor: 33 µg/mL per 1.0 A260 unit.
RNA conversion factor: 40 µg/mL per 1.0 A260 unit.
An A260/A280 ratio of ~1.8 is generally accepted as 'pure' for DNA, while ~2.0 is pure for RNA.
Check the A260/A230 ratio as well; values below 1.5 may indicate carbohydrate or phenol contamination.
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Fun Facts
"Nucleic acids absorb UV light at 260 nm due to the resonance structure of their nitrogenous bases (A, T, C, G)."
"Friedrich Miescher first isolated DNA in 1869, calling it 'nuclein'."
"NanoDrop small-volume spectrophotometers use surface tension to hold a 1-2 µL sample droplet between two optical pedestals."
"The Beer-Lambert Law assumes a linear relationship, which often breaks down at very high absorbance (>2.0 AU)."
