Aspartic acid's molecular formula is C4H7NO4 and has a molecular weight of 133.10 grams/mole. Aspartic acid is the one of only two amino acids that give a negatively charged carboxylic group on the side chain. The functional groups present within aspartic acid are an amine and two carboxylic groups. Aspartic acids are play a vital role as acids in enzyme active centers and also function in maintaining the solubility and ionic character of proteins. This amino acid is one of the only two acidic amino acids. There are three pKa values for aspartic acid which are: 1) alpha-carboxylic - 2.10; 2) alpha-amino - 9.82; 3) side chain - 3.86. The side chain is a carboxyl group located on the amino acid. The isoelectric point for aspartic acid is 2.77 pH.
Sources:
1. Mayer, Michael. "Aspartic acid information page. All about aspartic acid and the role it plays in your diet." Zest for Life vitamins and supplements. 24 Jan. 2011. 24 Mar. 2011 http://www.anyvitamins.com/aspartic-acid-info.html.
2. Kirste, Burkhard. "Aspartic Acid." Institut für Chemie und Biochemie an der FU Berlin. 23 Jan. 1998. 24 Mar. 2011 http://www.chemie.fu-berlin.de/chemistry/bio/aminoacid/asp_en.html.
3. "Amino Acids - Aspartic Acid." The Biology Project. 24 Sept. 2003. 24 Mar. 2011 http://www.biology.arizona.edu/biochemistry/problem_sets/aa/aspartate.html.
4. Parrill, Abby. "Amino Acid Structures." Michigan State University. 4 Feb. 1997. Department of Chemistry. 24 Mar. 2011 http://www.cem.msu.edu/~cem252/sp97/ch24/ch24aa.html.