Tunable fluorescent probes for detecting aldehydes in living systems.

Aldehydes, pervasive in various environments, pose health risks at elevated levels due to their collective toxic effects via shared mechanisms. Monitoring total aldehyde content in living systems is crucial due to their cumulative impact. Current methods for detecting cellular aldehydes are limited to UV and visible ranges, restricting their analysis in living systems. This study introduces an innovative reaction-based trigger that leverages the exceptional selectivity of 2-aminothiophenol for aldehydes, leading to the production of dihydrobenzothiazole and activating a fluorescence response. Using this trigger, we developed a series of fluorescent probes for aldehydes by altering the fluorophore allowing for excitation and emission wavelengths across the visible to near-infrared spectral regions without compromising the reactivity of the bioorthogonal moiety. These probes exhibit remarkable aldehyde chemoselectivity, rapid kinetics, and high quantum yields, enabling the detection of diverse aldehyde types, both exogenous and endogenous, within complex biological contexts. Notably, we employed the most red-shifted near-infrared probe from this series to detect aldehydes in living systems, including biliary organoids and mouse organs. These probes provide valuable tools for exploring the multifaceted roles of aldehydes in biological functions and diseases within living systems, laying the groundwork for further investigations.

Improved Triplex-Forming Isoorotamide PNA Nucleobases for A-U Recognition of RNA Duplexes.

Four new isoorotamide (Io)-containing PNA nucleobases have been designed for A-U recognition of double helical RNA. New PNA monomers were prepared efficiently and incorporated into PNA nonamers for binding A-U in a PNA:RNA2 triplex. Isothermal titration calorimetry and UV thermal melting experiments revealed slightly improved binding affinity for singly modified PNA compared to known A-binding nucleobases. Molecular dynamics simulations provided further insights into binding of Io bases in the triple helix. Together, the data revealed interesting insights into binding modes including the notion that three Hoogsteen hydrogen bonds are unnecessary for strong selective binding of an extended nucleobase. Cationic monomer Io8 additionally gave the highest affinity observed for an A-binding nucleobase to date. These results will help inform future nucleobase design toward the goal of recognizing any sequence of double helical RNA.

C-Terminal Arginine-Selective Cleavage of Peptides as a Method for Mimicking Carboxypeptidase B.

C-Terminal residues play a pivotal role in dictating the structure and functions of proteins. Herein, we report a mild, efficient, chemoselective, and site-selective chemical method that allows for precise chemical proteolysis at C-terminal arginine dictated by 9,10-phenanthrenequinone independent of the remaining sequence. This biomimetic approach also exhibits the potential to synthesize C-terminal methyl ester (-CO2Me) peptides.

Extended Peptide Nucleic Acid Nucleobases Based on Isoorotic Acid for the Recognition of A-U Base Pairs in Double-Stranded RNA.

Peptide nucleic acids (PNA) with extended isoorotamide containing nucleobases (Io ) were designed for binding A-U base pairs in double-stranded RNA. Isothermal titration calorimetry and UV thermal melting experiments revealed improved affinity for A-U using the Io scaffold in PNA. PNAs having four sequential Io extended nucleobases maintained high binding affinity.