What method is used for protein quantification at a wavelength of 280 nm?

The method used for protein quantification at a wavelength of 280 nm is based on aromatic absorption. Proteins contain aromatic amino acids, such as tryptophan and tyrosine, which absorb ultraviolet light at this wavelength. When a protein solution is placed in an ultraviolet (UV) spectrophotometer and the light at 280 nm passes through, the absorbance measured correlates with the concentration of these aromatic amino acids in the solution.

This property is particularly useful for quick estimations of protein concentrations without the need for complex reagents or lengthy procedures associated with some other quantification methods. The amount of light absorbed at 280 nm is directly proportional to the concentration of protein in the sample, allowing for a straightforward calculation based on the Beer-Lambert law.

In contrast, colorimetric assays, mass spectrometry, and chromatography utilize different principles and methods for quantifying proteins, making them generally less direct regarding absorbance measurements at 280 nm. Colorimetric assays rely on chemical reactions that produce a color change proportional to the protein concentration, while mass spectrometry measures the mass-to-charge ratio of ions, and chromatography separates components for analysis rather than directly measuring absorbance.