Protein Concentration Determination

Flashcards covering key vocabulary and concepts related to determining protein concentration using UV-light absorption and spectrophotometry.

UV-light Absorption

Proteins and peptides absorb UV-light in proportion to their aromatic amino acid content and total concentration.

Beer's Law

States that molar absorptivity is constant and absorbance is proportional to concentration for a given substance dissolved in a given solute and measured at a given wavelength.

Molar Absorptivity Units

M-1 cm-1

Wavelength for Protein Absorbance

Proteins are commonly measured at 280nm.

Transmittance (T)

The ratio of radiant power transmitted (P) by a sample to the radiant power incident (P0) on the sample: T = P/P0

Absorbance (A)

The logarithm (base 10) of the reciprocal of the transmittance: A = -log T = log (1/T)

Molar Extinction Coefficient (ε)

A measure of how strongly a chemical species absorbs light at a given wavelength.

Percent Solution Extinction Coefficient (εpercent)

Absorbance (A280nm) values for 1% (= 1g/100mL) solutions measured in a 1 cm cuvette, with units of (g/100mL)-1 cm-1.

BSA Extinction Coefficient

The absorptivity of BSA is generally ~6.6 for a 1% solution at 280nm.