1. What is the DNA Concentration Formula?

The DNA concentration formula calculates the concentration of DNA in a solution using UV absorbance at 260 nm (A₂₆₀), the extinction coefficient (ε), and the path length (l) of the spectrophotometer cuvette.

2. How Does the Calculator Work?

The calculator uses the DNA concentration equation:

Where:

• \( C \) — DNA concentration (μg/mL)
• \( A_{260} \) — Absorbance at 260 nm (unitless)
• \( \epsilon \) — Extinction coefficient (mL/μg/cm)
• \( l \) — Path length (cm)

Explanation: The equation relates the absorbance of DNA at 260 nm to its concentration, accounting for the specific absorbance properties of DNA (extinction coefficient) and the path length of the measurement.

3. Importance of DNA Concentration Measurement

Details: Accurate DNA concentration measurement is crucial for molecular biology experiments including PCR, sequencing, cloning, and other applications where precise DNA amounts are required.

4. Using the Calculator

Tips:

• Measure A₂₆₀ with a spectrophotometer
• Use standard extinction coefficient of 0.02 mL/μg/cm for dsDNA
• Standard path length is 1 cm for most cuvettes
• For ssDNA, use extinction coefficient of 0.033 mL/μg/cm

5. Frequently Asked Questions (FAQ)

Q1: What is the standard extinction coefficient for DNA?
A: For double-stranded DNA (dsDNA), the standard ε is 0.02 mL/μg/cm. For single-stranded DNA (ssDNA), it's 0.033 mL/μg/cm.

Q2: Why measure at 260 nm?
A: DNA absorbs UV light most strongly at 260 nm due to its purine and pyrimidine bases.

Q3: What affects the accuracy of the measurement?
A: Contaminants like proteins or RNA, air bubbles in the cuvette, and dirty cuvettes can affect accuracy.

Q4: How do I know my path length?
A: Standard cuvettes have 1 cm path length. Some microvolume instruments have different path lengths - check specifications.

Q5: What if my A₂₆₀ is too high?
A: For accurate measurements, A₂₆₀ should be between 0.1 and 1.0. Dilute your sample if it's too concentrated.