Question

A sample containing 2.7 x 10-4 M green fluorescent protein shows an absorbance of 0.651 at 509 nm. Calculate its molar absorptivity constant (ε).

Answer 1

To calculate the molar absorptivity constant (ε), we use the Beer-Lambert Law:

A = ε * c * l

where:
A is the absorbance,
ε is the molar absorptivity constant,
c is the concentration (in M),
l is the path length (in cm).

Given:
A = 0.651,
c = 2.7 x 10^(-4) M (or 2.7e-4 M),
l = unknown (we will solve for it).

We need to rearrange the equation to solve for ε:

ε = A / (c * l)

We need the value for l to calculate ε. The path length, l, is commonly 1 cm.

ε = 0.651 / (2.7e-4 M * 1 cm)

ε = 0.651 / 2.7e-4

ε ≈ 2.411 x 10^3 M^(-1) cm^(-1)

Therefore, the molar absorptivity constant (ε) is approximately 2.411 x 10^3 M^(-1) cm^(-1) for the sample containing 2.7 x 10^(-4) M green fluorescent protein.