Figure 1. The predominate forms of glutamine, glutamic acid, lysine and histidine as they occur at physiological pH.

From

The Identification of Amino Acids by Interpretation of Titration Curves: An Undergraduate Experiment for Biochemistry

Cassidy M. Dobson, Nathan S. Winter

World Journal of Chemical Education. 2014, 2(4), 59-61 doi:10.12691/wjce-2-4-3