This document provides instructions for calculating the concentration of single-stranded DNA (ssDNA) in micrograms per milliliter (μg/mL). It explains that an optical density (OD) reading of 1 at 260nm corresponds to 33 μg/mL of ssDNA. It then works through an example calculation where M13mp18 DNA diluted 10 μL into 1000 μL has an OD of 0.125, corresponding to a concentration of 4.125 μg/mL. To determine the original stock concentration, this value is multiplied by the dilution factor of 1000 μL/10 μL, giving a concentration of 412.5 μg/mL for the M13mp18 DNA stock solution.

1. Calculation of ssDNA
Concentration
DR. S. SIVASANKARA NARAYANI., M.SC., M.PHIL.,PH.D.,MRSB (UK)
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2. Single-stranded dna (ssdna) concentration expressed in µg/ml
To determine the concentration of single-stranded DNA (ssDNA) as a µg/ mL
amount, the following conversion factor is used:
1 OD of ssDNA = 33 µg/mL
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3. Single-stranded DNA isolated from M13mp18, a derivative of bacteriophage M13 used in
cloning and DNA sequencing applications, is diluted 10 µL into a total volume of 1000 µL
water. The absorbance of this diluted sample is read at 260 nm and an A260 value of 0.125 is
obtained. What is its concentration in µg/mL?
1 OD = 33 µg/mL
0.125 OD = x µg/mL ?
x µg/mL = 0.125 OD X 33 µg/mL
= 4.125 µg/mL
Therefore, the concentration of the diluted sample is 4.125 µg/mL
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4. To determine the concentration of the M13mp18 DNA stock solution, this value must be
multiplied by the dilution factor:
4.125 µg/mL X 1000µl/10µl = 4125 µg/mL /10
= 412.5 µg/mL
Therefore, the stock of M13mp18 DNA has a concentration of 412.5 µg/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
sivasan91@gmail.com
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