Peptide bonds ultraviolet absorption spectrum

VIII. The Ultraviolet Absorption Spectrum of the Peptide Bond and of the Polypeptide Fabric. 352... 

Using ultraviolet/visible (UV/Vis) absorption spectroscopy, it is possible to measure the protein concentration using Beer s Law A = e c, where A is the measured absorbance of a solution, e is the absorptivity of the protein, is the pathlength of the cell used to determine the absorbance, and c is the protein concentration. Proteins typically exhibit two strong, broad absorption bands in the UV/Vis part of the spectrum. The first and most intense band is centered at 214 nm and arises from absorption of light by the peptide backbone. The second absorption band is typically found at 280nm. This band arises from absorbance from the aromatic side chains of Trp, Tyr, and Phe. Disulfide bonds may exhibit weak absorption in this range as well. 

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