1. What is DNA Extinction Coefficient?

The DNA extinction coefficient (ε) measures how strongly DNA absorbs light at 260 nm wavelength. It is used to quantify DNA concentration in solution and is dependent on the base composition of the DNA molecule.

2. How Does the Calculator Work?

The calculator uses the DNA extinction coefficient equation:

Where:

• \( A \) — Adenine base count
• \( T \) — Thymine base count
• \( G \) — Guanine base count
• \( C \) — Cytosine base count
• 6600 — Extinction coefficient for A-T base pairs (M⁻¹ cm⁻¹ bp⁻¹)
• 1980 — Extinction coefficient for G-C base pairs (M⁻¹ cm⁻¹ bp⁻¹)

Explanation: The equation accounts for different extinction coefficients of A-T and G-C base pairs due to their distinct absorption properties at 260 nm.

3. Importance of DNA Extinction Coefficient

Details: Accurate extinction coefficient calculation is crucial for determining DNA concentration using UV spectrophotometry, which is essential for molecular biology applications like PCR, sequencing, and cloning.

4. Using the Calculator

Tips: Enter the count of each nucleotide base (A, T, G, C) in your DNA sequence. All values must be non-negative integers representing the actual base composition.

5. Frequently Asked Questions (FAQ)

Q1: Why do A-T and G-C base pairs have different extinction coefficients?
A: A-T base pairs absorb more strongly at 260 nm than G-C base pairs due to differences in their molecular structure and electronic properties.

Q2: How is the extinction coefficient used to calculate DNA concentration?
A: Concentration = Absorbance at 260 nm / (Extinction coefficient × Path length), using Beer-Lambert law.

Q3: What is a typical extinction coefficient range for DNA?
A: For double-stranded DNA, extinction coefficients typically range from 6,000 to 8,000 M⁻¹ cm⁻¹ per base pair, depending on base composition.

Q4: Does this calculation work for single-stranded DNA?
A: No, this equation is specifically for double-stranded DNA. Single-stranded DNA has different extinction coefficients and requires separate calculation methods.

Q5: How accurate is this estimation method?
A: This method provides a good approximation for most applications, but for precise quantification, experimental determination using known standards is recommended.