Aspartic acid, for example, possesses one protonated amine and two deprotonated carboxyl groups, for a net charge of −1 at physiological pH.
ɐspˈɑːɹɾɪk ˈæsɪd, fɔːɹ ɛɡzˈæmpəl, pəzˈɛsᵻz wˈʌn pɹˈoʊtənˌeɪɾᵻd ˈæmaɪn ænd tˈuː dᵻpɹˈoʊtənˌeɪɾᵻd kˈɑːɹbəksˌɪl ɡɹˈuːps, fɚɹə nˈɛt tʃˈɑːɹdʒ ʌv mˈaɪnəs wˈʌn æt fˌɪzɪəlˈɑːdʒɪkəl pˈiː ˈeɪtʃ.