Final answer:
The net charge on the peptide TKPIVPMEYGK at pH 7 is -1.
Step-by-step explanation:
The peptide sequence given is TKPIVPMEYGK. To estimate the net charge on the peptide at pH 7, we need to determine the charges of each amino acid at pH 7 and sum them up.
At pH 7, the carboxyl group (COOH) of an amino acid is deprotonated (lost a proton) and carries a negative charge (-1), while the amino group (NH2) is protonated (gained a proton) and carries a positive charge (+1). Since there are no histidine residues in the sequence, we can ignore the imidazole side chain charge.
Using the one-letter abbreviations of the amino acids, the charges at pH 7 for each amino acid in the sequence are:
- T (Thr): 0
- K (Lys): +1
- P (Pro): 0
- I (Ile): 0
- V (Val): 0
- A (Ala): 0
- P (Pro): 0
- M (Met): 0
- E (Glu): -1
- Y (Tyr): -1
- G (Gly): 0
- K (Lys): +1
Summing up the charges, the net charge on the peptide at pH 7 is -1 + 1 - 1 - 1 + 1 = -1.