One of the most common methods for analyzing protein characteristics and measuring protein purity in solution is to observe the sample’s absorption of ultraviolet (UV) wavelengths of light. Proteins that contain the appropriate amino acids are absorbent to light on the UV-spectrum, specifically light with peak wavelengths of 260 – 280 nanometers (nm). This makes it easy to analyze various protein characteristics and to measure concentration relative to a standard or using a pre-defined extinction coefficient.

In this blog post, RQM+ Lab Services will focus on the use of UV absorbance spectroscopy as a method of determining protein characteristics.


Imaging Protein Characteristics with UV Absorbance

Two amino acids are primarily responsible for the UV absorbance of proteins: tryptophan and tyrosine. Each of these demonstrates a molar absorption coefficient at a wavelength of 280nm, but the peak absorbance of the protein itself is largely determined by the concentration and arrangement of these specific amino acids within the linear chain. The minimum and maximum UV absorbance of proteins subsequently vary as a function of amino acid composition. This provides a rudimentary method of measuring the purity of known proteins and amino acid concentration in protein mixtures or unknown samples.

The simplest technique for quantifying the amount of protein in solution is to directly measure UV-absorbance with a spectrometer. Samples are exposed to UV light with wavelengths from 260 – 280m and the extent of absorption is measured. This technique is ideal for rapid and simple measurement of pure proteins containing the tryptophan and tyrosine aromatic chains.

This technique is subsequently unsuitable for analysing protein characteristics of samples that do not contain tryptophan and tyrosine. Often, peak wavelengths of 205nm are used to spectroscopically interrogate such recalcitrant samples using UV-Vis spectroscopy.


Testing Protein Characteristics with RQM+ Lab Services

RQM+ Lab Services is one of the world’s leading authorities in laboratory testing of complex samples, with a suite of analytical tools and dedicated professionals available to assist with your protein characteristics testing processes. If you would like to learn more about protein testing with RQM+ Lab Services, please do not hesitate to contact us directly.

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