Calculate the DNA concentration of each of the samples
- A 1mg/ml solution of pure DNA in a 1cm path length cuvette should give an absorbance at 260nm of 20 (A2601cm, 1mg/ml = 20.0) Thus, a 50µg/ml solution (sample F3) should yield A260 = 1.0.
- Find out the DNA concentrations in your samples (Kiwi extract, F1, F2 & F3) based on this information (DNA A2601cm, 1mg/ml = 20.0) and your absorbance measurements.
Calculate the A260/280 ratios for the samples
- The ‘260/280 ratio’ is an indication of DNA purity. Anything above 1.5 for this ratio (has no ‘units’ because it is a ratio) is good. For pure DNA this value should be ~1.8. Values above 2.0 should be treated with suspicion (some contaminant may be absorbing at 260nm), whereas values below 1.5 suggest significant protein contamination (or something else absorbing light energy at 280nm such as detergent).