Calculating Tyrosine Molar Absorption Coefficient
This problem requires calculating the molar absorption coefficient ($\epsilon$) using the Beer-Lambert Law, given the absorbance (A), concentration (c), and path length (l) of a solution.
Beer-Lambert Law Application
The Beer-Lambert Law relates absorbance to concentration and path length:
$A = \epsilon \times c \times l$
Where:
- $A$ is the absorbance (unitless).
- $\epsilon$ is the molar absorption coefficient ($M^{-1}cm^{-1}$).
- $c$ is the molar concentration ($M$).
- $l$ is the path length ($cm$).
Calculation Steps
We need to rearrange the Beer-Lambert Law to solve for $\epsilon$:
$ \epsilon = \frac{A}{c \times l} $
Given values:
- Absorbance, $A = 0.75$
- Concentration, $c = 5 \times 10^{-4}$ $M$
- Path length, $l = 1$ $cm$
Substitute the values into the rearranged formula:
$ \epsilon = \frac{0.75}{(5 \times 10^{-4} \text{ M}) \times (1 \text{ cm})} $
Perform the calculation:
$ \epsilon = \frac{0.75}{5 \times 10^{-4}} \text{ M}^{-1}\text{cm}^{-1} $
$ \epsilon = \frac{0.75}{0.0005} \text{ M}^{-1}\text{cm}^{-1} $
$ \epsilon = 1500 \text{ M}^{-1}\text{cm}^{-1} $
Final Result
The calculated molar absorption coefficient is 1500 $M^{-1}cm^{-1}$. The question asks for the value correct to the nearest integer, which is 1500.
Important Questions from Enzyme Assays Molar Extinction Coefficient
- A solution shows a transmittance of 20% when taken in a cuvette of 2.5 cm path length. If the molar absorption coefficient of the solution is $12000 \text{ dm}^3/\text{mol.cm}$, the concentration of the solution is ________ $\times 10^5 \text{ mol/dm}^3$ (rounded off to two decimal places).
- A solution containing GTP has molar extinction coefficient of $1.55 \times 10^4$ $mol^{-1}dm^3cm^{-1}$ at a given wavelength. The concentration of GTP solution is $1.290 \times 10^{-5}$ $mol$ $dm^{-3}$. The absorbance of GTP solution in 1 cm cuvette at the same wavelength will be .................
- An enzyme preparation has activity of 2 Units per 20 $\mu$l, and protein concentration 0.4 mg/ml. The specific activity (Units/mg) of this enzyme will be ________
- Measurement of the absorbance of a solution containing NADH in a path length of 1cm cuvette at 340 nm shows the value of 0.31. The molar extinction coefficient of NADH is $6200 M^{-1} cm^{-1}$. The concentration of NADH in the solution is ________ $\mu M$ (correct to integer number).
- If a $10$ mM solution of a biomolecule in a cuvette of path length $10$ mm absorbs $90\%$ of the incident light at $280$ nm, the molar extinction coefficient of the biomolecule at this wavelength is ________ $M^{-1}cm^{-1}$. (Round off to two decimal places)
