Replacing alanine by which amino acid will increase UV absorbances of protein at 280 nm wavelength
Aromatic amino acids absorb UV light, which has absorption maxima between 275 nm-285 nm.
Tryptophan has greater absorption in this region than other two aromatic amino acids (tyrosine, phenylalanine).
Since nearly all proteins contain aromatic amino acids, the amount of light absorbed at 280 nm by protein is used as an indirect measure of protein concentration.
Leucine
Proline
Arginine
Tryptophan