Calculation of ds DNA

1. Calculation of dsDNA
Concentration
DR. S. SIVASANKARA NARAYANI., M.SC., M.PHIL.,PH.D.,MRSB (UK)
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2. Formula
 The formula that describes the relationship between absorption at 260nm
(A260), concentration (c) (in mg/mL), the light path length (l) of the cuvette (in
centimeters), and the extinction coefficient at 260 nm (E260) for a 1 cm light
path is
A 260 = E260 l c
Note: The absorption value of 20 for a 1 mg DNA/mL solution is referred to as
DNA’s extinction coefficient.
This relationship is known as Beer’s Law. Since the light path, l, is 1, this
equation becomes
A260 = E260 c
c = A260/ E260
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3. A DNA solution has an A260 value of 0.5. What is the
DNA concentration in µg DNA/mL?
c = A260/ E260
c = 0.5 / 20 = 0.025 mg DNA/mL
0.025 mg DNA/mL X 1000 µg /mg
= 25 µg DNA/mL
 Therefore, the sample has a concentration of 25 µg DNA/mL.
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4. Try it📝
A DNA solution has an A260 value of 1.0. What is the
DNA concentration in µg DNA/mL?
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5. Reference
 Calculations for molecular biology and Biotechnology – A Guide to
mathematics in the laboratory, Second Edition – Frank. H. Stephenson
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