A friend who studies in NUS tells you that the extinction coefficient (ε260) of double strand DNA is 50 ng cm-1 µL. Which of the following options is correct if you measured A260 =... A friend who studies in NUS tells you that the extinction coefficient (ε260) of double strand DNA is 50 ng cm-1 µL. Which of the following options is correct if you measured A260 = 0.9 (L = 1 cm)?
Understand the Problem
The question involves calculating the concentration of double-stranded DNA based on the extinction coefficient and the absorbance measured at 260 nm. The A260 value of 0.9 and the extinction coefficient are provided, which will be used to determine the DNA concentration in appropriate units.
Answer
The DNA concentration calculated is $18 \, \mu\text{g/mL}$.
Answer for screen readers
The calculated DNA concentration is $18 , \mu\text{g/mL}$.
Steps to Solve
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Use the formula for DNA concentration calculation
The concentration of DNA can be calculated using the formula:
$$ \text{Concentration} = \frac{A_{260}}{\epsilon_{260} \times L} $$
where:
- ( A_{260} ) = absorbance at 260 nm (given as 0.9)
- ( \epsilon_{260} ) = extinction coefficient (given as 50 ng cm(^{-1}) μL)
- ( L ) = path length of the cuvette (given as 1 cm)
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Convert units of the extinction coefficient
Since the extinction coefficient is given in ng cm(^{-1}) μL, we need to convert it to μg cm(^{-1}) mL to be consistent with common DNA concentration units.
$$ \epsilon_{260} = 50 \text{ ng cm}^{-1} , \mu\text{L} = 0.05 \text{ μg cm}^{-1} , \text{mL} $$ -
Substitute values into the formula
Now we can substitute the known values into the concentration formula:
$$ \text{Concentration} = \frac{0.9}{0.05 \times 1} $$ -
Calculate the concentration
Perform the calculation:
$$ \text{Concentration} = \frac{0.9}{0.05} = 18 \text{ μg/mL} $$ -
Check given options for the correct answer
Review the calculated concentration against the provided options to determine the correct answer.
The calculated DNA concentration is $18 , \mu\text{g/mL}$.
More Information
The extinction coefficient relates absorbance to concentration and is essential for determining nucleic acid concentrations in molecular biology. The calculated value indicates a concentration that can be easily used in experimental applications.
Tips
- Confusing units: Ensure that extinction coefficients and other measurements are expressed in compatible units such as μg/mL instead of ng/μL.
- Miscalculating absorbance values: Always double-check mathematical operations to avoid computation errors.
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