N-Cyanorhodamines: cell-permeant, photostable and bathochromically shifted analogues of fluoresceins

Authors:

Lukas Heynck, Jessica Matthias, Mariano L. Bossi, Alexey N. Butkevich, Stefan W. Hell

Keywords:

Dyes, Fluorescent probes, STED, Cyanorhodamines

Abstract:

Fluorescein and its analogues have found only limited use in biological imaging because of the poor photostability and cell membrane impermeability of their O-unprotected forms. Herein, we report rationally designed N-cyanorhodamines as orange- to red-emitting, photostable and cell-permeant fluorescent labels negatively charged at physiological pH values and thus devoid of off-targeting artifacts often observed for cationic fluorophores. In combination with well-established fluorescent labels, self-labelling protein (HaloTag, SNAP-tag) ligands derived from N-cyanorhodamines permit up to four-colour confocal and super-resolution STED imaging in living cells.

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