4
Nucleic Acid Applications
Measure Oligo DNA or Oligo RNA
Thermo Scientific
NanoDrop Eight User Guide 39
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/µl 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.
Summary of Contents for NanoDrop Eight
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