Direct optical measurement of intramolecular distances with angstrom precision.

Optical investigations of nanometer distances between proteins, their subunits, or other biomolecules have been the exclusive prerogative of Förster resonance energy transfer (FRET) microscopy for decades. In this work, we show that MINFLUX fluorescence nanoscopy measures intramolecular distances down to 1 nanometer-and in planar projections down to 1 angstrom-directly, linearly, and with angstrom precision. Our method was validated by quantifying well-characterized 1- to 10-nanometer distances in polypeptides and proteins.

β-Galactosidase- and Photo-Activatable Fluorescent Probes for Protein Labeling and Super-Resolution STED Microscopy in Living Cells.

We report on the synthesis of two fluorescent probes which can be activated by β-Galactosidase (β-Gal) enzymes and/or light. The probes contained 2-nitro-4-oxybenzyl and 3-nitro-4-oxybenzyl fragments, with β-Gal residues linked to C-4. We performed the enzymatic and photoactivation of the probes in a cuvette and compared them, prior to the labeling of fusion protein in live cells with overexpressed β-galactosidase.

Photoactivatable Carbo- and Silicon-Rhodamines and Their Application in MINFLUX Nanoscopy.

New photoactivatable fluorescent dyes (rhodamine, carbo- and silicon-rhodamines [SiR]) with emission ranging from green to far red have been prepared, and their photophysical properties studied. The photocleavable 2-nitrobenzyloxycarbonyl unit with an alpha-carboxyl group as a branching point and additional functionality was attached to a polycyclic and lipophilic fluorescent dye. The photoactivatable probes having the HaloTagTM amine (O2) ligand bound with a dye core were obtained and applied for live-cell staining in stable cell lines incorporating Vimentin (VIM) or Nuclear Pore Complex Protein NUP96 fused with the HaloTag.

MINSTED nanoscopy enters the Ångström localization range.

Super-resolution techniques have achieved localization precisions in the nanometer regime. Here we report all-optical, room temperature localization of fluorophores with precision in the Ångström range. We built on the concept of MINSTED nanoscopy where precision is increased by encircling the fluorophore with the low-intensity central region of a stimulated emission depletion (STED) donut beam while constantly increasing the absolute donut power.

Chalcone-Supported Cardiac Mesoderm Induction in Human Pluripotent Stem Cells for Heart Muscle Engineering.

Human pluripotent stem cells (hPSCs) hold great promise for applications in cell therapy and drug screening in the cardiovascular field. Bone morphogenetic protein 4 (BMP4) is key for early cardiac mesoderm induction in hPSC and subsequent cardiomyocyte derivation. Small-molecular BMP4 mimetics may help to standardize cardiomyocyte derivation from hPSCs.

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

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).

Photoactivatable Fluorophore for Stimulated Emission Depletion (STED) Microscopy and Bioconjugation Technique for Hydrophobic Labels.

The use of photoactivatable dyes in STED microscopy has so far been limited by two-photon activation through the STED beam and by the fact that photoactivatable dyes are poorly solvable in water. Herein, we report ONB-2SiR, a fluorophore that can be both photoactivated in the UV and specifically de-excited by STED at 775 nm. Likewise, we introduce a conjugation and purification protocol to effectively label primary and secondary antibodies with moderately water-soluble dyes.

Palladium-Catalyzed 4-Fold Domino Reaction for the Synthesis of a Polymeric Double Switch.

A palladium-catalyzed 4-fold domino reaction consisting of two carbopalladation reactions and two C-H activation reactions, followed by the introduction of an acrylate moiety, led to the tetra-substituted helical alkene A2, using the dialkyne A3 as a substrate. The alkene was copolymerized with butyl acrylate by using the reversible addition-fragmentation chain transfer polymerization (RAFT) to give the desired polymeric switch A1.

1-(2-Hydroxy-2-methyl-3-phenoxypropanoyl)indoline-4-carbonitrile derivatives as potent and tissue selective androgen receptor modulators.

We present a novel series of selective androgen receptor modulators (SARMs) which shows excellent biological activity and physical properties. 1-(2-Hydroxy-2-methyl-3-phenoxypropanoyl)-indoline-4-carbonitriles showed potent binding to the androgen receptor (AR) and activated AR-mediated transcription in vitro. Representative compounds demonstrated diminished activity in promoting the intramolecular interaction between the AR carboxyl (C) and amino (N) termini.