Answer is: the ionized state of the carboxyl group is COO⁻.
Physiological pH is 7,4 and carboxyl group in the R group has pKa = 3,7. Since this pKa is lower than physiological pH of 7,4, carboxyl group (COOH) will lost proton, and because of that it will be deprotonated and will have negative charge.
Aspartic acid is an α-amino acid that is used in the biosynthesis of proteins.