1. What is DNA Concentration?

DNA concentration refers to the amount of DNA present in a given volume of solution, typically measured in nanograms per microliter (ng/µL). Accurate measurement is essential for molecular biology applications.

2. How Does the Calculator Work?

The calculator uses the standard DNA concentration equation:

Where:

• \( A_{260} \) — Absorbance at 260 nm (dimensionless)
• 50 — Conversion factor for dsDNA (ng/µL per absorbance unit)
• dilution_factor — Factor by which sample was diluted (dimensionless)

Explanation: DNA absorbs UV light at 260 nm, and this absorbance is proportional to its concentration. The 50 ng/µL factor is specific for double-stranded DNA.

3. Importance of DNA Quantification

Details: Accurate DNA concentration measurement is crucial for PCR, sequencing, restriction digests, and other molecular techniques where precise DNA amounts are required.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why is 260 nm used for DNA quantification?
A: DNA nucleotides absorb UV light most strongly at 260 nm, making this wavelength ideal for concentration measurements.

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: Does this work for RNA or ssDNA?
A: No, RNA uses a factor of 40 ng/µL, and ssDNA uses 33 ng/µL instead of the 50 ng/µL for dsDNA.

Q4: What affects A260 accuracy?
A: Contaminants like protein or phenol can affect readings. The A260/A280 ratio should be ~1.8 for pure DNA.

Q5: How should I dilute my sample?
A: Dilute in the same buffer used for blanking the spectrophotometer, typically TE buffer or nuclease-free water.