Biochemistry HW QUESTION-I am stuck! Please help!

Question

Indicate which of the amino acid residues in the following peptide sequence contains a group that has a negative charge for its most likely charge state at pH 10.

Thr-Glu-Trp-Lys-Ser-Asn-Ile-Gly-Gln

Answer 1

At pH 10, glutamic acid (GLU) should have a negative charge since it has a -COOH side chain. At elevated pH, the side chain carboxyl group would lose a proton forming a negative charge.

R-COOH + OH^- ==> R-COO^- + H₂O