Rhodamines with a Chloronicotinic Acid Fragment for Live Cell Superresolution STED Microscopy**

Abstract

Formylation of 2,6‐dichloro‐5‐R‐nicotinic acids at C‐4 followed by condensation with 3‐hydroxy‐N,N‐dimethylaniline gave analogs of the popular TAMRA fluorescent dye with a 2,6‐dichloro‐5‐R‐nicotinic acid residues (R=H, F). The following reaction with thioglycolic acid is selective, involves only one chlorine atom at the carbon between pyridine nitrogen and the carboxylic acid group and affords new rhodamine dyes absorbing at 564/ 573 nm and emitting at 584/ 597 nm (R=H/ F, in aq. PBS). Conjugates of the dyes with “small molecules” provided specific labeling (covalent and non‐covalent) of organelles as well as of components of the cytoskeleton in living cells and were combined with fluorescent probes prepared from 610CP and SiR dyes and applied in two‐color STED microscopy with a 775 nm STED laser.

Subtle Structural Translation Magically Modulates the Super-Resolution Imaging of Self-Blinking Rhodamines

“…Rhodamine is the adequate fluorophore scaffold for super-resolution imaging credited to their robust photophysical properties − and self-blinking possibilities from thermal spirocyclization equilibrium . In a landmark work, Urano et al first introduced a self-blinking rhodamine (HMSiR) for SMLM imaging through optimizing intramolecular nucleophilic fluorophores .…”

Subtle Structural Translation Remarkably Modulates the Super-Resolution Imaging of Self-blinking Rhodamines

“…Rhodamine is the adequate fluorophore scaffold for super-resolution imaging credited to their robust photophysical properties, [13][14][15][16][17][18][19][20][21] and self-blinking possibilities from thermo spirocyclization equilibrium. 22 In a landmark work, Urano et al first introduced a self-blinking rhodamine (HMSiR) for SMLM imaging through optimizing of intramolecular nucleophilic fluorophores.…”

A Stimulated Emission Depletion (STED) Microscope of All Trades

“…It requires labels able to reach their target without disrupting membrane structures, in addition to being bright, stable, and specific. An excellent example are abberior's LIVE dyesorganic dyes with optimized chemical modifications, which make them membrane-permeable and useful already at very low concentrations [11][12][13][14]. Depending on the residual group, they can be used either for direct labeling of DNA, actin, tubulin, or lysosomes, or attached to a fusion protein, for example a SNAP®-tag.…”