UV Absorbance 280 nm Protein Determination. Simple and quick method to accurately quantitate total protein in purified material or approximately quantitate total protein in crude lysates or partial purified material. Quantitation of the amount of protein in a solution is possible in a simple spectrometer. Absorption of radiation in the near UV by proteins depends on the Tyr and Trp content (and to a very small extent on the amount of Phe and disulfide bonds). Dr. Mario Lebendiker