Protein Concentration Measurement Methods

A set of vocabulary flashcards to aid in understanding key concepts related to protein concentration measurement methods and relevant chemical reactions.

Kjeldahl method

A standard method for determining protein concentration by measuring nitrogen content.

Degradation

The first step in the Kjeldahl method where proteins are broken down in the presence of H2SO4.

Dumas method

A faster method for measuring nitrogen content by combustion, compared to Kjeldahl.

Beer-Lambert Law

A principle stating that absorbance is directly proportional to the concentration of a solution.

Scopes method

A method used to measure protein concentration by absorbance at 205 nm.

Pace method

A method for measuring protein concentration using absorbance at 280 nm.

biuret reaction

A reaction involving the interaction of cupric ions and peptide bonds to yield a violet color.

BCA method

A protein assay method that combines the biuret reaction with bicinchoninic acid for detection.

Lowry method

A method that detects proteins using the Folin–Ciocalteu reagent and measures absorbance at 750 nm.

Coomassie dye

A dye used in protein assays that binds to basic amino acids and gives a color change.

1,8-ANS

A fluorescent dye that binds to hydrophobic regions of proteins for quantification.

melamine

A compound that acts as a fake protein; its contamination led to health crises.

extinction coefficient ( ε )

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

absorbance

The amount of light absorbed by a sample, measured in spectroscopy.

detection limit

The smallest concentration of a substance that can be reliably detected or quantified.

fluorescamine method

A fluorescence-based assay that reacts with primary amines to quantify proteins.

intrinsic fluorescence

The fluorescence emitted by proteins, often measured to determine protein concentration.

aggregation correction

Methods to account for the effects of protein aggregates on measurements.

pathlength ( l )

The distance light travels through a sample in a cuvette, a critical factor in optical measurements.

molar concentration ( C )

The number of moles of a solute in a liter of solution.

anionic dye

A negatively charged dye used for binding to positively charged amino acids in proteins.

absorbance maxima

The wavelength at which a substance exhibits peak absorbance.

amino acids with aromatic rings

Amino acids like tryptophan and tyrosine that significantly contribute to protein absorbance.

nephrotoxicity

A toxic effect on the kidneys, often resulting from exposure to certain chemicals.

garbage term

Informal term indicating something irrelevant or not scientifically valid.

titration

A laboratory method used to determine the concentration of a solution by reacting it with a standard solution.

nitrogen concentration

The amount of nitrogen in a sample, a key measure in protein quantification.

UV-VIS spectroscopy

A technique that involves measuring the absorbance of UV and visible light by a sample.

characterization methods

Techniques to analyze and describe the properties of proteins.

standard curve

A graph used to determine concentrations based on absorbance data.

conversion factor

A value used to convert nitrogen concentrations to protein concentrations.

ionic strength

The measure of the concentration of ions in a solution, affecting protein behavior.

viscosity

A measure of a fluid's resistance to flow, important in protein solutions.

sensitivity

The ability of a method to detect small changes in concentration.

non-covalent binding

Interactions between molecules that do not involve covalent bonds, important in dye-protein bindings.

What are the three main steps of the Kjeldahl method?

1. Degradation: Proteins are digested in H2SO4.

2. Distillation: Ammonia (NH3) is released and collected.

3. Titration: The amount of collected ammonia is measured to quantify nitrogen.

Name two common nitrogen-based methods for protein quantification.

The Kjeldahl method and the Dumas method.

Which methods utilize direct UV-Vis absorbance for protein concentration measurement?

The Scopes method (at 205 nm) and the Pace method (at 280 nm).

List common colorimetric or dye-binding assays used for protein quantification.

The biuret reaction, BCA method, Lowry method, and methods using Coomassie dye.

What are some fluorescence-based methods for determining protein concentration?

The fluorescamine method, 1,8-ANS binding, and intrinsic fluorescence.

Which fluorescence-based protein assay quantifies proteins by reacting specifically with primary amines?

The fluorescamine method.