<prompt> Replacing alanine by which amino acid, will increase UV absorbance of protein at 280 nm wavelength?TryptophanArginineGuanineLysine  <response>: Aromatic side chains are responsible for the UV absorption of most proteins, which have absorption maxima between 275 nm and 285 nm Basically, this absorption of UV-light is because of conjugated double bonds present in the ring. Aromatic amino acids: Tryptophan Tyrosine Phenylalanine Absorption ismaximum for tryptophan. Since nearly all proteins contain aromatic amino acids, the amount of light absorbed at 280 nm by a protein is used as an indirect measure of protein concentration. 