Ultraviolet absorbance by proteins

Proteins in solution absorb ultraviolet light with absorbance maxima at 280 and 200 nm. Amino acids with aromatic rings are the primary reason for the absorbance peak at 280 nm. Peptide bonds are primarily responsible for the peak at 200 nm. Secondary, tertiary, and quaternary structure all affect absorbance, therefore factors such as pH, ionic strength, etc. can alter the absorbance spectrum. Tyrosine and tryptophan absorb more than do phenylalanine; tryptophan is responsible for most of the absorbance of ultraviolet light (ca. 280 nm) by proteins. Tyrosine is the only one of the aromatic amino acids with an ionizable side chain. DNA absorbance peak at 260 nm. #protein #polypeptide #ultravioletAbsorbance #proteinQuantification #UltravioletDNA #NikolaysGeneticsLessons #aminoAcid #peptide #disulfideBridges #covalentBounding #ionicBounding #hydrophobicInteraction #proteinStructure #proteinSequence #proteinFolding #aminoAcids #proteins #Polypeptides #ImidazolRing #Histidine #polypeptideChain #oligopeptide #hydrolysesSynthesis #condensationReaction #Genetics