Surface-capping ligands on quantum dots (QDs) modify the physical and chemical properties of QDs to enable diverse applications. Accurate qualitative and quantitative analyses of these ligands are therefore essential for the advancement of QD research; however, conventional methods (e.g., UV–vis, TEM) seldom provide direct stoichiometric insight. MS can offer a solution, but traditional MALDI induces an excessive ligand loss. Here, we employed a highly electronegative, fluorinated porphyrin (TPFP) as a soft MALDI matrix for CdSe QDs to preserve the ligands and yield high ion signals at reduced laser power. Comparative studies with electron-transfer matrixes (DCTB, 9-nitroanthracene, dithranol, and pentacene) indicate that the highly electronegative TPFP extracts electrons from photoexcited QDs, lowering ionization thresholds and preventing ligand detachment. Using TPFP-MALDI-MS, we determined QD core sizes and counted the number of surface ligands in carboxylate- and thiolate-capped QDs, and for thiolate-capped QDs in particular, we further evaluated ligand numbers and ligand densities with various core sizes. This approach provides a reliable strategy to determine QD core sizes, to count ligand numbers, and to estimate the surface coverage with improved resolution. These findings underscore the importance of electron affinity of a matrix for soft ionization and expand MS-based tools for probing QD core and surface chemistry, paving the way for more reliable characterization of nanocrystalline systems.

Diamines are well-known bidentate ligands that coordinate with metal cations; however, their solvation behavior with ionic clusters remains largely unexplored. In this study, we investigated the structures of lithium iodide ionic clusters solvated by ethylenediamine and N,N,N′,N′-tetramethylethylenediamine using electrospray ionization(ESI)–ion mobility spectrometry–mass spectrometry. Interestingly, diamines were found to stabilize ionic clusters by bridging two metal cations, even though such structures are not the most thermodynamically stable in the gas phase. We propose that these bridging structures were likely formed and kinetically trapped in the solution phase or in the highly concentrated droplets generated during the ESI process. Furthermore, we analyzed the effects of alkali metal and halide identity on solvation behavior.

Rutin, a sugar-bonded flavonoid, exhibits anti-obesity potential but has limited bioavailability unless hydrolyzed to isoquercetin or further to quercetin. This study evaluated Lactiplantibacillus plantarum HAC03 (HAC03), isolated from Korean white kimchi, as an effective facilitator of rutin bioavailability. HAC03 rapidly converted rutin into isoquercetin and, at a slower rate, to quercetin both in vitro and in vivo. Unlike HAC03-only or rutin-only groups, co-administration of HAC03 and rutin synergistically reduced body weight, adipocyte size, and obesity biomarkers by suppressing fat synthesis and enhancing fatty acid β-oxidation in diet-induced obese mice. HAC03, together with rutin, colonized the ileum and enriched polyphenol-metabolizing gut microbes. At 30 min post-administration, isoquercetin—more bioavailable and effective than its precursor, rutin—peaked (∼9 μM) in mouse portal vein blood, while remaining minimal or undetectable in controls. This pairing of functional flavonoid and tailored probiotic synergistically combats obesity via ileal isoquercetin conversion, offering a promising single-flavonoid, single-probiotic obesity-management strategy.

To enable efficient anionic polymerization without metal catalysts and co-modulators, conjugate-addition polymerization of (meth)acrylic monomers was conducted using carbodicarbene (CDC) coordinated with N-heterocyclic carbene and cyclic (alkyl)(amino)carbene. As the sole organic initiator, CDC showed high activity and polymerization efficiency when used with different (meth)acrylic monomers, including methacrylates with functional groups. The role of CDC as an initiator was supported by nanoelectrospray ionization mass spectrometry.

We investigated the gas-phase isomerism and stability of host–guest complexes formed between cucurbiturils (CB[6] and CB[7]) and three n,n′-bipyridine regioisomers (n = 2, 3, and 4), focusing on how molecular geometry and charge distribution influence complex formation. Ion mobility spectrometry-mass spectrometry and collision-induced dissociation experiments, supported by density functional theory (DFT) calculations, reveal distinct inclusion and exclusion complex isomers. Singly-protonated bipyridines tend to form exclusion complexes with CB[6], while doubly-protonated forms enable stable inclusion through enhanced charge–portal interactions. CB[7], with its larger and more flexible cavity, consistently supports inclusion for all bipyridine isomers, regardless of charge state. These findings emphasize the importance of charge localization, host flexibility, and phase-specific effects in supramolecular assembly, which may further offer valuable insights for designing bipyridine- or bipyridinium-based materials.

Cost-effective redox-active materials are essential for advancing redox flow batteries (RFBs). Iron, with its abundance and suitability as a redox couple, is a promising candidate; however, achieving stable and fast redox reactions in aqueous RFBs remains a challenge. This study presents an Fe-based negolyte stabilized by a hexadentate ligand, where Fe–ligand bonds are enhanced through intermolecular interactions. The sulfonate-substituted Fe complex exhibits a formal potential of −0.44 V versus Ag/AgCl and an exceptionally high rate constant of 0.69 cm s−1. Near-neutral RFBs incorporating 0.5 M Fe complex show excellent cycling stability, with no discernible capacity fading over 300 cycles. This performance is attributed to intermolecular hydrogen bonds that reinforce Fe–ligand coordination and promote the formation of stable trimeric clusters. Operando electrochemical Raman spectroscopy and density functional theory reveal that π-backdonation from Fe(II) to the imino-phenolate moiety further stabilizes the complex after reduction. In contrast, the hydroxyl-substituted complex exhibits inferior stability due to weaker hydrogen bonding and less pronounced π-backdonation. These findings underscore the importance of ligand design and intermolecular interactions in developing cost-effective, high-performance redox-active materials for aqueous RFBs.

The ribosome polymerizes L-α-amino acids into polypeptides, catalyzing peptide bond formation through aminolysis. This process is facilitated by entropy trapping within its peptidyl transferase center (PTC). In this research, we harness this capability to synthesize polymers containing cyclic motifs in the backbone. We design 26 non-canonical monomers (ncMs) with two distinct substrates: dicarboxylic esters and hydrazinoesters, each containing bifunctional moieties that undergo ring-closing reactions through multiple aminolysis reactions. Using a cell-free system that enables the consecutive incorporation of these ncMs into a growing peptide, we discover that the ribosome can produce 5- and 6-membered cyclic backbones, which have never been reported. We also demonstrate that the formation of such cyclic backbones within the ribosome is tunable by altering the substituents of dicarboxylic esters. This discovery expands the range of non-standard backbones that can be synthesized by the ribosome and motivates future research towards expanding ribosome-mediated chemistries for biopolymer synthesis.

Au-based alloy nanoclusters (NCs) have attracted significant interest due to their unique properties, including chirality, magnetism, luminescence, and size-dependent characteristics. Despite their promising potential, further efforts are required to explore a broader range of ligands and alloy NCs to fully unlock their capabilities. Here, [Au13Cu4(MBA)12]3– alloy NCs (MBA = mercaptobenzoic acid) were synthesized from [Au25(MBA)18]− seed NCs using MBA isomers as etching agents. The [Au25(MBA)18]− NCs were fragmented and reassembled with Cu ions into [Au13Cu4(MBA)12]3– NCs. This process, driven by MBA ligands, was monitored by time-dependent electrospray ionization mass spectrometry and optical spectroscopies. Theoretical calculations suggested a tetrahedral geometry for the [Au13Cu4(MBA)12]3– NCs stabilized by interligand interactions. Notably, the quantum yield of [Au13Cu4(p-MBA)12]3– NCs increased ∼14-fold compared to that of [Au25(p-MBA)18]− NCs. These results offer a novel approach for synthesizing water-soluble, size-focused Au-based alloy NCs, opening up the investigation of new gold alloy clusters with enhanced properties and broader applications.

Organic dyes play a crucial role in live-cell imaging because of their advantageous properties, such as photostability and high brightness. Here we introduce a super-photostable and bright organic dye, Phoenix Fluor 555 (PF555), which exhibits an order-of-magnitude longer photobleaching lifetime than conventional organic dyes without the requirement of any anti-photobleaching additives. PF555 is an asymmetric cyanine structure in which, on one side, the indole in the conventional Cyanine-3 is substituted with 3-oxo-quinoline. PF555 provides a powerful tool for long-term live-cell single-molecule imaging, as demonstrated by the imaging of the dynamic single-molecule interactions of the epidermal growth factor receptor with clathrin-coated structures on the plasma membrane of a live cell under physiological conditions.

DNA-encoded library (DEL) technology is a powerful tool for discovering potent ligands for biological targets but constrained by limitations, including the insolubility of DNA in organic solvents and its instability under various reaction conditions, which restrict the reactivity scope and structural diversity achievable in library synthesis. Here, we present a new strategy called nanoDEL, where library molecules and DNA tags are displayed on the surface of nanoparticles. Since nanoparticles disperse well in both organic solvents and aqueous solutions, DEL synthesis can be accomplished using well-established organic solvent-based conditions, eliminating the need for aqueous conditions. Moreover, nanoDEL enables air-sensitive reactions that are inaccessible with conventional DEL methods relying on aqueous conditions. Notably, in nanoDEL, multiple copies of a DNA tag are attached to an individual nanoparticle to encode a single compound, significantly enhancing tolerance to DNA-damaging conditions. Even when most DNA tags are damaged, sequence analysis remains feasible via amplification of intact tags. Consequently, nanoDEL facilitates the convenient use of existing organic reactions without the necessity to develop DNA-compatible reactions. The potential of nanoDEL was validated by affinity selection against streptavidin as a model system and successfully applied to the discovery of potent small-molecule inhibitors for a kinase and stapled peptide inhibitors targeting a protein–protein interaction, exhibiting dissociation constants in the nanomolar range. Furthermore, we demonstrated that a large combinatorial library can be efficiently synthesized on nanoparticles using a synthetic scheme including moisture-sensitive reaction steps, which are not feasible with conventional DELs.