Class: BE-210
Group: W1
Members: Curtis Li, Robert Pierson, Vinay Bhawnani, Armaghan Farooq
Date: April 30, 1997
Full Text

Abstract:
Using simple acid-base apparatus, we have completed titrating different mixtures of aspartic acid, glutamic acid and lysine. We report here the pKa values of aspartic acid, glutamic acid, 50-50 mol % aspartic acid plus glutamic acid, and three different mixtures of aspartic acid plus lysine (25-75 mol %, 50-50 mol %, 75-25 mol %). Studies of the titration curve showed there are three pKa values for aspartic acid, glutamic acid and mixture of aspartic acid plus glutamic acid; studies also showed there are two pKa values for mixture of aspartic acid plus lysine. Analyzing our data using the Henderson-Hasselbalch equation, and plotted and slope vs. pH, led us to determine various pKa values. The two higher pKa values of aspartic acid were determined to be 3.835 + 0.072 and 9.696 + 0.038; the two higher pKa values of glutamic acid were calculated to be 4.088 + 0.064 and 9.562 + 0.061. In addition, the pKa values of 50-50 mol % aspartic acid plus glutamic acid lie in between the pKa values of pure aspartic acid and pure glutamic acid. The pKa values are 3.948 + 0.021 and 9.677 + 0.026. Plus the average pKa values for 25-75, 50-50, and 75-25 mol % of aspartic acid plus lysine were determined to be 9.969 + 0.041, 9.848 + 0.070, and 9.767 + 0.034, respectively. Our results suggest two general concepts. First, solutions of mixed amino acids should have similar ionic properties as those of its constituents if every amino acid constituent has similar ionic properties. Secondly, the ionic properties of a solution containing both acidic amino acid and basic amino acid will depend on the relative concentration of the amino acids.