The structure of tryptophan is shown at the right along with the pK values of the α-carboxyl and α-amino groups. (pK1=2.38; pK2=9.39)

Tryptophan is a diprotic acid which can exist in three protonated forms: H2A , HA0, and A–. (HA0 consists primarily of the zwitterionic form with a negatively charged carboxyl group and positively charged amino group, but a very small amount of the completely neutral species does exist). Calculate the fraction (α) of αH2A , αHA0, and αA– present at pH 2.60.