Elementary plant Biochemistry and Biotechnology (2+1)

b) Amino acids with non-polar aromatic R groups

 
• This group includes phenylalanine, tyrosine and tryptophan. All these amino acids participate in hydrophobic interactions, which is stronger than aliphatic R groups because of stacking one another . Tyrosine and tryptophan are more polar than phenylalanine due to the presence of hydroxyl group in tyrosine and nitrogen in the indole ring of tryptophan.The absorption of ultraviolet (UV) light at 280 nm by tyrosine, tryptophan and to a lesser extent by phenylalanine is responsible for the characteristic strong absorbance of light by proteins. This property is exploited in the characterization and quantification of proteins.