RNA Concentration from A260 Calculator

RNA Concentration Formula:

\[ C = A_{260} \times 40 \times DF \]

RNA Concentration:

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1. What is RNA Concentration from A260?

The A260 method is a standard way to quantify RNA concentration using UV spectrophotometry. RNA absorbs UV light at 260 nm, and this absorbance is proportional to its concentration.

2. How Does the Calculator Work?

The calculator uses the standard RNA concentration formula:

\[ C = A_{260} \times 40 \times DF \]

Where:

\( C \) — RNA concentration (ng/μL)
\( A_{260} \) — Absorbance at 260 nm (unitless)
\( 40 \) — Conversion factor for RNA (ng/μL per 1 A260 unit)
\( DF \) — Dilution factor (unitless)

Explanation: Pure RNA has an extinction coefficient of 40 μg/mL for 1 A260 unit. The calculator converts this to ng/μL and accounts for any sample dilution.

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 critical.

4. Using the Calculator

Tips:

Measure A260 using a spectrophotometer with RNA in solution
Enter the actual A260 reading (typically between 0.1-1.0 for accurate measurement)
If the sample was diluted, enter the dilution factor (e.g., if diluted 1:10, enter 10)
For undiluted samples, use DF = 1

5. Frequently Asked Questions (FAQ)

Q1: Why is 40 used as the conversion factor?
A: RNA has an extinction coefficient of 40 μg/mL for 1 A260 unit in a 1 cm pathlength cuvette. This accounts for RNA's specific UV absorption properties.

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

Q3: How does dilution affect the calculation?
A: The dilution factor (DF) accounts for any pre-measurement dilution. Multiply the measured A260 by DF to get the original sample's concentration.

Q4: What about RNA purity (A260/A280 ratio)?
A: While this calculator determines concentration, a good A260/A280 ratio (1.8-2.0) indicates pure RNA. Lower ratios suggest protein contamination.

Q5: Does this work for all RNA types?
A: Yes, the 40 ng/μL factor works for most RNA types (mRNA, rRNA, tRNA), though very short oligonucleotides may require adjustment.