Which of the following amino acids have side chains that are negatively charged under physiological conditions?: (A) Aspaic acid, (B) Histidine, (C) Tyrosine, (D) Serine
Answer is A. The side chains of the acidic amino acids, aspaic acid and glutamic acid, are negatively charged above pH 3; in their ionized state, they are often referred to as aspaate and glutamate. Asparagine and glutamine are, respectively, the amides of aspaic acid and glutamic acid. Ref: Voet Fundamentals of Biochemistry 4th Edition Pg no 82.