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 like PCR, sequencing, and cloning.

2. How Does the Calculator Work?

The calculator uses the standard DNA concentration formula:

Where:

• \( A_{260} \) — Absorbance at 260 nm (optical density)
• 50 — Conversion factor for double-stranded DNA (ng/µL per AU)
• Dilution factor — How much the sample was diluted before measurement

Explanation: DNA absorbs UV light at 260 nm, and this absorbance is proportional to its concentration. The 50 ng/µL factor is based on the extinction coefficient of DNA.

3. Importance of DNA Quantification

Details: Accurate DNA concentration measurement is crucial for ensuring consistent results in downstream applications, optimizing reaction conditions, and preventing experimental failures.

4. Using the Calculator

Tips: Enter the A260 reading from your spectrophotometer and the dilution factor used (if any). For undiluted samples, use 1 as the dilution factor.

5. Frequently Asked Questions (FAQ)

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

Q2: What's a good A260 range?
A: Ideal readings are between 0.1-1.0 AU. Values outside this range may be less accurate due to instrument limitations.

Q3: How does purity affect the calculation?
A: Contaminants like protein or phenol can affect A260. The A260/A280 ratio (ideally ~1.8) indicates purity.

Q4: Is this calculation different for RNA or ssDNA?
A: Yes - RNA uses 40 ng/µL/AU and ssDNA uses 33 ng/µL/AU as conversion factors instead of 50.

Q5: What if my sample was diluted?
A: Multiply the result by your dilution factor (e.g., for a 1:100 dilution, multiply by 100).