1. What is the A260 DNA Concentration Calculation?

The A260 method is a standard way to estimate DNA concentration using UV absorbance at 260 nm. DNA absorbs UV light at this wavelength, and the absorbance is proportional to its concentration in solution.

2. How Does the Calculator Work?

The calculator uses the standard DNA concentration formula:

Where:

• \( C \) — DNA concentration (ng/μL)
• \( A_{260} \) — Absorbance reading at 260 nm
• \( 50 \) — Conversion factor for double-stranded DNA (50 ng/μL per 1 A260 unit)
• \( DF \) — Dilution factor (if sample was diluted)

Explanation: Pure double-stranded DNA has an extinction coefficient of 50 ng/μL for each 1.0 absorbance unit at 260 nm. The dilution factor accounts for any sample dilution prior to measurement.

3. Importance of Accurate DNA Quantification

Details: Accurate DNA concentration measurement is essential for molecular biology applications like PCR, sequencing, and cloning, where precise DNA amounts are critical for success.

4. Using the Calculator

Tips: Enter the A260 reading from your spectrophotometer and the dilution factor (if undiluted, use 1). The calculator will provide the DNA concentration in ng/μL.

5. Frequently Asked Questions (FAQ)

Q1: Why is 50 used as the conversion factor?
A: For double-stranded DNA, 1 A260 unit corresponds to 50 ng/μL. For single-stranded DNA or RNA, different factors are used (33 and 40 respectively).

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

Q3: How do I determine the dilution factor?
A: If you diluted your sample (e.g., 2 μL DNA + 18 μL water), DF = total volume/sample volume (20/2 = 10 in this case).

Q4: What affects A260 accuracy?
A: Contaminants like proteins or phenol, air bubbles, and dirty cuvettes can affect readings. The A260/A280 ratio helps assess purity.

Q5: Can I use this for RNA concentration?
A: No, for RNA use 40 instead of 50 in the calculation (C = A260 × 40 × DF).