UV Vis Absorbance in Proteins

One of the most common techniques used for measuring protein purity in solution and analyzing protein characteristics is to observe the sample’s absorption of ultraviolet (UV) wavelengths of light.

Image Credit: Jordi Labs

Proteins containing the appropriate amino acids are absorbent to light on the UV-spectrum, specifically light that has peak wavelengths of 260 – 280 nanometers (nm).

This makes it simple to analyze many protein characteristics and to measure concentration relative to a standard or by utilizing a pre-defined extinction coefficient. Jordi Labs will focus on the utilization of UV absorbance spectroscopy as a technique for establishing protein characteristics in this article.

Imaging Protein Characteristics with UV Absorbance

There are two amino acids that are primarily responsible for the UV absorbance of proteins: tyrosine and tryptophan. Both have a molar absorption coefficient at a wavelength of 280 nm, but the peak absorbance of the protein itself is largely determined by the arrangement and concentration of these specific amino acids within the linear chain.

Subsequently, the maximum and minimum UV absorbance of proteins vary as a function of amino acid composition. This supplies a rudimentary technique of measuring the purity of known proteins and amino acid concentration in unknown samples or protein mixtures.

Directly measuring UV-absorbance using a spectrometer is the simplest way to quantify the amount of protein in solution. The extent of absorption is measured while samples are exposed to UV light with wavelengths from 260 – 280 nm.

This method is ideal for simple, quick measurement of pure proteins containing the tyrosine and tryptophan aromatic chains.

Subsequently, it is unsuitable for analyzing protein characteristics of samples which do not contain tyrosine and tryptophan. Usually, peak wavelengths of 205 nm are utilized to spectroscopically interrogate such recalcitrant samples via UV-Vis spectroscopy.

Testing Protein Characteristics with Jordi Labs

With a range of analytical tools and dedicated professionals available to assist with protein characteristics testing processes, Jordi Labs is one of the world’s leading authorities in laboratory testing of complex samples.

This information has been sourced, reviewed and adapted from materials provided by Jordi Labs.

For more information on this source, please visit Jordi Labs.

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