A) The pK1, pK2, and pKR for the amino acid histidine are 1.8, 9.3, and 6.0, respectively. At pH 4.0 would be charged predominantly as follows: A. a-carboxylate 0, a-amino +1, imidazole +1, net charge +2
B. a-carboxylate +1, a-amino +1, imidazole −1, net charge +1
C. a-carboxylate −1, a-amino +1, imidazole 0, net charge 0
D. a-carboxylate +1, a-amino 0, imidazole −1, net charge 0
E. a-carboxylate −1, a-amino +1, imidazole +1, net charge +1
b) The pK1, pK2, and pKR for the amino acid arginine are 1.8, 9.0, and 12.5, respectively. At pH 7.0 arginine would be charged predominantly as follows:
A. a-carboxylate +1, a-amino 0, guanidino -1, net charge 0
B. a-carboxylate 0, a-amino 0, guanidino +1, net charge +1
C. a-carboxylate −1, a-amino +1, guanidino +1, net charge +1
D. a-carboxylate −1, a-amino 0, guanidino +1, net charge 0
E. a-carboxylate +1, a-amino −1, guanidino −1, net charge −1
c) The pK1, pK2, and pKR for the amino acid aspartic acid are 2.0, 9.9, and 3.9, respectively. At pH 7.0, aspartic acid would be charged predominantly as follows:
A. a-carboxylate +1, a-amino +1, b-carboxylate +1, net charge +3
B. a-carboxylate 0, a-amino +1, b-carboxylate 0, net charge +1
C. a-carboxylate 0, a-amino −1, b-carboxylate 0, net charge −1
D. a-carboxylate +1, a-amino −1, b-carboxylate +1, net charge +1
E. a-carboxylate −1, a-amino +1, b-carboxylate −1, net charge −1