Fig. 2.

(a) Absorbance spectrum of each conjugate without SDS (solid line) and with SDS (dashed line), and at neutral pH (black) and acidic (red) conditions. The blue shifted peak without SDS represents H-dimer formation of fluorophores. Both pHrodo and TAMRA showed H-dimer formation. (b) Fluorescence spectra of each conjugate without SDS (solid line) and with SDS (dashed line). The fluorescence was increased by SDS addition (H-dimer dissociation) in both pHrodo and TAMRA conjugates. In addition, pHrodo probes showed fluorescence activation by lowering pH, and this effect resulted in the large fluorescence activation capacity for pHrodo conjugates.