Aspartic Acid

Aspartic acid, also known as aspartate, is an amino acid with an acidic side chain. At normal pH it usually carries a negative charge. This is due to a missing proton from the -COOH (carboxylic acid) group.
It is coded for by the the three letter code Asp and the one letter code D.

Berg, Tymoczko and Stryer. (2006) Biochemistry, 6th edition, New York: WH Freeman : page 32

References Berg, Tymoczko and Stryer. (2006) Biochemistry, 6th edition, New York: WH Freeman