1. What is RNA Concentration Calculation?

The RNA concentration calculation estimates the amount of RNA in a solution using absorbance measurements at 260 nm (A₂₆₀). This is based on the principle that nucleic acids absorb UV light at this wavelength.

2. How Does the Calculator Work?

The calculator uses the standard RNA concentration formula:

Where:

• \( C \) — RNA concentration (ng/μL)
• \( A_{260} \) — Absorbance at 260 nm (unitless)
• \( 40 \) — Extinction coefficient for RNA (μg/mL per 1 OD unit)
• \( DF \) — Dilution factor (unitless)

Explanation: Pure RNA has an extinction coefficient of ~40 μg/mL for each 1.0 OD unit at 260 nm. The dilution factor accounts for any sample dilution prior to measurement.

3. Importance of RNA Quantification

Details: Accurate RNA quantification is essential for downstream applications like RT-qPCR, RNA sequencing, and other molecular biology techniques where precise RNA amounts are required.

4. Using the Calculator

Tips: Enter the A₂₆₀ reading from your spectrophotometer. If you diluted your sample before measurement, enter the dilution factor (e.g., if you diluted 1:10, enter 10).

5. Frequently Asked Questions (FAQ)

Q1: Why is 40 used in the calculation?
A: 40 is the average extinction coefficient for RNA (μg/mL per 1 OD unit), based on the absorbance properties of RNA nucleotides.

Q2: What is a good A260 reading?
A: For accurate measurements, A₂₆₀ should ideally be between 0.1 and 1.0. Values outside this range may be less reliable.

Q3: How does this differ from DNA concentration calculation?
A: DNA calculations typically use 50 instead of 40 as the extinction coefficient, since DNA absorbs slightly more UV light than RNA.

Q4: What affects the accuracy of this measurement?
A: Contaminants like proteins or phenol can affect absorbance. The A₂₆₀/A₂₈₀ ratio should be ~2.0 for pure RNA.

Q5: Should I use this for very dilute samples?
A: For samples with very low concentrations, consider using fluorescence-based methods (e.g., Qubit) which are more sensitive.