Measure Oligo DNA or Oligo RNA
Thermo Scientific NanoDrop One User Guide 51
Related Topics
• Calculations for Nucleic Acid Measurements
The five nucleotides that comprise DNA and RNA exhibit
widely varying A260/A280 ratios. Estimated A260/A280
ratios for each independently measured nucleotide are
provided below:
Guanine: 1.15
Adenine: 4.50
Cytosine: 1.51
Uracil: 4.00
Thymine: 1.47
The A260/A280 ratio for a specific nucleic acid sequence
is approximately equal to the weighted average of the
A260/A280 ratios for the four nucleotides present.
Note: RNA will typically have a higher 260/280 ratio due
to the higher ratio of Uracil compared to that of Thymine.
Reported Values
• Nucleic acid concentration. Reported in selected unit (i.e., ng/μL,
μg/uL or μg/mL). Calculations are based on modified Beer’s Law
equation using corrected nucleic acid absorbance value.
• A260/A280 purity ratio. Ratio of corrected absorbance at 260 nm to
corrected absorbance at 280 nm.
• A260/A230 purity ratio. Ratio of corrected absorbance at 260 nm to
corrected absorbance at 230 nm.
Note: The traditional purity ratios (A260/A280 and A260/A230), which
are used as indicators of the presence of various contaminants in nucleic
acid samples, do not apply for oligonucleotides because the shapes of their
spectra are highly dependent on their base compositions. See side bar for
more information.
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