1. What is DNA Concentration Calculation?

The DNA concentration calculation estimates the amount of DNA in a solution based on its absorbance at 260nm (A₂₆₀). This is a fundamental measurement in molecular biology for quantifying DNA samples.

2. How Does the Calculator Work?

The calculator uses the standard DNA concentration formula:

Where:

• \( C \) — DNA concentration (ng/μL)
• \( A_{260} \) — Absorbance at 260nm (unitless)
• \( DF \) — Dilution factor (unitless)
• 50 — Conversion factor for double-stranded DNA (ng·mL^-1 per absorbance unit)

Explanation: Pure double-stranded DNA has an extinction coefficient of 50 ng·mL^-1 per absorbance unit at 260nm. The dilution factor accounts for any sample dilution prior to measurement.

3. Importance of DNA Quantification

Details: Accurate DNA quantification is essential for downstream applications like PCR, sequencing, and cloning, where precise DNA amounts are required for optimal results.

4. Using the Calculator

Tips: Enter the measured A₂₆₀ value from your spectrophotometer. If you diluted your sample before measurement, enter the dilution factor (e.g., if you diluted 1:10, enter 10).

5. Frequently Asked Questions (FAQ)

Q1: Why is 260nm used for DNA measurement?
A: DNA absorbs UV light most strongly at 260nm due to its aromatic nucleotide bases, making this wavelength ideal for quantification.

Q2: What is a good A₂₆₀ reading range?
A: Ideal readings are between 0.1-1.0. Values outside this range may be less accurate due to instrument limitations.

Q3: What if my sample was diluted?
A: Multiply the result by your dilution factor. For example, if you diluted 1:100 and get 5 ng/μL, your actual concentration is 500 ng/μL.

Q4: Does this work for RNA or single-stranded DNA?
A: No, RNA uses 40 instead of 50, and single-stranded DNA uses 33. Different conversion factors apply.

Q5: What affects the accuracy of this measurement?
A: Contaminants that absorb at 260nm (like RNA or free nucleotides), turbidity, and improper blanking can affect accuracy.