Unfortunately, in Table 1 of the original article the association constants for the compounds 4’-MAHF and 4’-EAHF extrapolated for pH=1 are not correct. The correct values are 8×106M-1 and 5×106M-1 for 4’-MAHF and 4’-EAHF, respectively, and not 8×105M-1 and 5×105M-1 as originally reported. The corrected table is shown below. The discussion and conclusions were based on the correct values and therefore this error has no influence on them. We apologize to all readers for any inconvenience this error might have caused. (Table Presented).