Replacing alanine by which amino acid, will increase UV absorbance of protein at 280 nm wavelength?

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.