Conformational probe: static quenching is reduced upon acid triggered ring flip of a myo-inositol derivative

Abstract

The aromatic rings in 4- O-dabsyl-6- O-dansyl- myo-inositol-1,3,5-orthoformate ( 6) participate in electron transfer causing static quenching as detected by the absence of fluorescence. Upon addition of acid, the orthoformate lock is cleaved, with subsequent conformational change of the myo-inositol ring from penta-axial to the more stable penta-equatorial chair, which causes some increase in fluorescence due to spatial separation of fluorophore and a quencher and reduction in static quenching. In the case of 4,6- O-bisdansyl- myo-inositol-1,3,5-orthoformate ( 3), the acid-induced removal of the orthoformate lock leads to substantial change of fluorescence following spatial separation of two dansyl groups.