What is the expected absorbance of a solution of DNA that has a concentration of 34.00 ng DNA/μL?

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1 answer

To determine the expected absorbance of a solution of DNA at a concentration of 34.00 ng/μL, we can use the absorbance formula based on the Beer-Lambert Law.

The absorbance (A) can be calculated using the following formula:

\[ A = \epsilon \cdot c \cdot l \]

Where:

  • \( A \) = Absorbance
  • \( \epsilon \) = Molar absorptivity (L/(mol·cm))
  • \( c \) = Concentration (mol/L)
  • \( l \) = Path length (cm)

For nucleic acids, a common value for the molar absorptivity (\( \epsilon \)) at 260 nm is approximately 0.020 (optical density per ng/μL).

  1. Convert the concentration from ng/μL to μg/mL:

    • 34.00 ng/μL = 34.00 μg/mL
  2. Use the typical conversion that 1 μg/mL of DNA corresponds to an absorbance of approximately 0.020 at 260 nm. Thus: \[ A = \text{Concentration (μg/mL)} \times 0.020 \]

  3. Substitute the given concentration: \[ A = 34.00 , \text{μg/mL} \times 0.020 = 0.68 \]

Thus, the expected absorbance of the solution is 0.68.