Synthesis of an azido-tagged low affinity ratiometric calcium sensor

Abstract

Changes in high localised concentrations of Ca2+ ions are fundamental to cell signalling. The synthesis of a dual excitation, ratiometric calcium ion sensor with a Kd of 90 μM, is described. It is tagged with an azido group for bioconjugation, and absorbs in the blue/green and emits in the red region of the visible spectrum with a large Stokes shift. The binding modulating nitro group is introduced to the BAPTA core prior to construction of a benzofuran-2-yl carboxaldehyde by an allylation–oxidation–cyclisation sequence, which is followed by condensation with an azido-tagged thiohydantoin. The thiohydantoin unit has to be protected with an acetoxymethyl (AM) caging group to allow CuAAC click reaction and incorporation of the KDEL peptide endoplasmic reticulum (ER) retention sequence.

Emission pathway switching by solvent polarity: Facile synthesis of benzofuran-bipyridine derivatives and turn-on fluorescence probe for zinc ions

“…[7][8][9][10][11][12] Among various fluorescent molecules, a benzofuran moiety has been utilized as a skeleton of many fluorophores presumably due to its strong emission with high quantum yield and facile synthesis. [13][14][15][16][17] In general, elongated conjugation was required to further bring the absorption and emission maximum to the visible region. Therefore, direct functionalization of benzofurans with electronic components can be beneficial to facilitate adjustment of their photophysical properties.…”