Substitution of which one of the following amino acids in place of alanine would increase the absorbance of protein at 280 nm -
Leucine
Arginine
Tryptophan
Prolein
Ans. is 'c' i.e., Tryptophan Most Amino acids do not absorb visible light and are thus colourless.However aromatic aminoacids absorb ultraviolet light.This accounts for the characteristic strong absorbance of light by most proteins at a wavelength of 280 nm, a property exploited by researchers in the characterization of proteins;Tryptophan makes the major contribution to the ability of most proteins to absorb light in the region of 280 nmAlso know,Other amino acids which absorb lightTyrosinePhenylalanineMeasurement of light absorption by a spectrophotometer is used to detect and identify molecules and to measure their concentration in solution.
Biological Function of Proteins