DNA Extinction Coefficient Calculator

DNA Extinction Coefficient Equation:

\[ \varepsilon = \sum \varepsilon_{base} \times Length + Corrections \]

Extinction Coefficient (ε):

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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 essential for molecular biology applications.

2. How Does the Calculator Work?

The calculator uses the DNA extinction coefficient equation:

\[ \varepsilon = \sum \varepsilon_{base} \times Length + Corrections \]

Where:

\( \varepsilon \) — Total extinction coefficient (M⁻¹ cm⁻¹)
\( \varepsilon_{base} \) — Base-specific extinction coefficient
\( Length \) — Number of bases in sequence
\( Corrections \) — Additional correction factors

Base Coefficients (ε₂₆₀):

Adenine (A): 15,400 M⁻¹ cm⁻¹
Thymine (T): 8,800 M⁻¹ cm⁻¹
Guanine (G): 11,500 M⁻¹ cm⁻¹
Cytosine (C): 7,400 M⁻¹ cm⁻¹

3. Importance of Extinction Coefficient

Details: The extinction coefficient is crucial for determining DNA concentration, purity assessment (A260/A280 ratio), and accurate quantification in PCR, sequencing, and other molecular techniques.

4. Using the Calculator

Tips: Enter the DNA sequence (A, T, G, C only), sequence length in bases, and any additional correction factors. The calculator will compute the total extinction coefficient at 260 nm.

5. Frequently Asked Questions (FAQ)

Q1: Why is extinction coefficient important for DNA quantification?
A: It allows conversion of absorbance readings at 260 nm to molar concentration using Beer-Lambert law: Concentration = A₂₆₀ / ε.

Q2: What are typical extinction coefficient values?
A: For double-stranded DNA, ε is approximately 50 µg/mL per 1.0 A₂₆₀ unit. Single-stranded DNA has higher ε values due to unstacked bases.

Q3: How does sequence composition affect extinction coefficient?
A: AT-rich sequences have higher extinction coefficients than GC-rich sequences due to higher absorbance of adenine and thymine bases.

Q4: When are correction factors needed?
A: Correction factors account for buffer effects, temperature variations, secondary structure, or modified bases that alter absorbance.

Q5: Can this be used for RNA and modified nucleotides?
A: RNA has different base coefficients. Modified nucleotides require specific extinction coefficients not included in this calculator.