pK data from Bull, "An Introduction to Physical Biochemistry", p128.

Note: only Arg, Tyr, Lys, Cys, His, Glu, Asp, and the amino and carboxyl
      termini should be specified in this file. All other values are ignored.
Specify the amino terminus by using the residue name NH2.
Specify the carboxyl terminus by using the residue name COOH.

Residue      pK    ..

C           8.3
D           3.91
E           4.25
H           6.50
K          10.79
R          12.50
Y          10.95

NH2         8.56
COOH        3.56