1. What is DNA Concentration Calculation?

DNA concentration calculation using UV spectrophotometry is a standard method in molecular biology to determine the concentration of nucleic acids in a solution. The calculation is based on the absorbance at 260nm (A260), which DNA molecules strongly absorb.

2. How Does the Calculator Work?

The calculator uses the DNA concentration formula:

Where:

• \( A260 \) — Absorbance reading at 260nm
• \( 50 \) — Extinction coefficient for double-stranded DNA (50 ng/μL for 1 AU)
• \( Dilution \) — Dilution factor of the sample

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

3. Importance of DNA Concentration Measurement

Details: Accurate DNA quantification is essential for various molecular biology applications including PCR, sequencing, cloning, and transfection experiments. Proper concentration ensures optimal reaction conditions and reproducible results.

4. Using the Calculator

Tips: Enter the A260 absorbance value (typically between 0.1-1.0 for accurate measurement) and the dilution factor applied to your sample before measurement. Ensure spectrophotometer is properly blanked with appropriate buffer.

5. Frequently Asked Questions (FAQ)

Q1: Why is 50 used as the multiplication factor?
A: The factor 50 comes from the extinction coefficient for double-stranded DNA, where 1 absorbance unit at 260nm corresponds to 50 ng/μL of double-stranded DNA.

Q2: Does this calculation work for RNA or single-stranded DNA?
A: No, RNA and single-stranded DNA have different extinction coefficients (40 ng/μL for RNA and 33 ng/μL for ssDNA per 1 AU at 260nm).

Q3: What is the ideal A260 range for accurate measurement?
A: The optimal range is 0.1-1.0 absorbance units. Values outside this range may be less accurate due to instrument limitations.

Q4: How does sample purity affect the calculation?
A: Contaminants like proteins, phenol, or RNA that absorb at 260nm can interfere with accuracy. Always check the A260/A280 ratio (ideally 1.8-2.0) for pure DNA.

Q5: When should I use this calculation versus other methods?
A: UV spectrophotometry is suitable for pure DNA samples. For contaminated samples or very dilute solutions, consider fluorometric methods like Qubit which are more specific for DNA.