Synthesis and screening of a library of Lewisx deoxyfluoro-analogues reveals differential recognition by glycan-binding partners.

Glycan-mediated interactions play a crucial role in biology and medicine, influencing signalling, immune responses, and disease pathogenesis. However, the use of glycans in biosensing and diagnostics is limited by cross-reactivity, as certain glycan motifs can be recognised by multiple biologically distinct protein receptors. To address this specificity challenge, we report the enzymatic synthesis of a 150-member library of site-specifically fluorinated Lewisx analogues ('glycofluoroforms') using naturally occurring enzymes and fluorinated monosaccharides. Subsequent incorporation of a subset of these glycans into nanoparticles or a microarray revealed a striking spectrum of distinct binding intensities across different proteins that recognise Lewisx. Notably, we show that for two proteins with unique binding sites for Lewisx, glycofluoroforms exhibited enhanced binding to one protein, whilst reduced binding to the other, with selectivity governed by fluorination patterns. We finally showcase the potential diagnostic utility of this approach in glycofluoroform-mediated bacterial toxin detection by lateral flow.

Aryl-Substituted Acridine Donor Derivatives Modulate the Transition Dipole Moment Orientation and Exciton Harvesting Properties of Donor-Acceptor TADF Emitters.

Thermally activated delayed fluorescence (TADF) compounds are highly attractive as sensitizing and emitting materials for organic light-emitting diodes (OLEDs). The efficiency of the OLED depends on multiple parameters, most of which rely on the properties of the emitter including those that govern the internal quantum and outcoupling efficiencies. Herein, we investigate a series of aryl substituted acridine donor derivatives of the donor-acceptor TADF emitter DMAC-TRZ, with the objective of correlating their properties, such as triplet harvesting efficiency and transition dipole moment orientation, with their corresponding device efficiency. The decoration of the DMAC donor with substituted aryl groups not only modifies the molecular weight and length of the emitter but also affects the emission color and the capacity for the emitters to efficiently harvest triplet excitons. The presence of electron-withdrawing 4-cyanophenyl and 4-trifluoromethylphenyl groups in, respectively, CNPh-DMAC-TRZ and CF3Ph-DMAC-TRZ, blue-shifts the emission spectrum but slows down the reverse intersystem crossing rate constant (k RISC), while the opposite occurs in the presence of electron-donating groups in t BuPh-DMAC-TRZ and OMePh-DMAC-TRZ (red-shifted emission spectrum and faster k RISC). In contrast to our expectations, the OLED performance of the five DMAC-TRZ derivatives does not scale with their degree of horizontal emitter orientation but follows the k RISC rates. This, in turn, demonstrates that triplet harvesting (and not horizontal emitter orientation) is the dominant effect for device efficiency using this family of emitters. Nonetheless, highly efficient OLEDs were fabricated with t BuPh-DMAC-TRZ and OMePh-DMAC-TRZ as emitters, with improved EQEmax (∼28%) compared to the reference DMAC-TRZ devices.

Molecular asymmetry and rigidification as strategies to activate and enhance thermally activated delayed fluorescence in deep-blue MR-TADF emitters.

Two novel deep-blue multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters, 1B-CzCrs and 2B-CzCrs, containing a fused carbazole unit were synthesized. The carbazole contributed to the emergence of TADF in these small molecules. Particularly, organic light-emitting diodes with 1B-CzCrs doped in the mCP host achieve a maximum external quantum efficiency of 12.8% at CIE coordinates of (0.146, 0.062).

Biophysical and structural analyses of the interaction between the SHANK1 PDZ domain and an internal SLiM.

The PDZ (Postsynaptic density protein-95[PSD-95]/Discs-large) domain, prevalent as a recognition module, has attracted significant attention given its ability to specifically recognize ligands with consensus motifs (also termed PDZ binding motifs [PBMs]). PBMs typically bear a C-terminal carboxylate as a recognition handle and have been extensively characterized, whilst internal ligands are less well known. Here we characterize a short linear motif (SLiM) - EESTSFQGP - as an internal PBM based on its strong binding affinity towards the SHANK1 PDZ domain (SHANK1656-762 hereafter referred to as SHANK1). Using the acetylated analogue Ac-EESTSFQGP-CONH2 as a competitor for the interaction of SHANK1 with FAM-Ahx-EESTSFQGP-CONH2 or a typical fluorophore-labelled C-terminal PBM - GKAP - FITC-Ahx-EAQTRL-COOH - the internal SLiM was demonstrated to show comparable low-micromolar IC50 by competition fluorescent anisotropy. To gain further insight into the internal ligand interaction at the molecular level, we obtained the X-ray co-crystal structure of the Ac-EESTSFQGP-CONH2/SHANK1 complex and compared this to the Ac-EAQTRL-COOH/SHANK1 complex. The crystallographic studies reveal that the SHANK1 backbones for the two interactions overlap significantly. The main structural differences were shown to result from the flexible loops which reorganize to accommodate the two PBMs with distinct lengths and terminal groups. In addition, the two C-terminal residues Gly and Pro in Ac-EESTSFQGP-CONH2 were shown not to participate in interaction with the target protein, implying further truncation and structural modification using peptidomimetic approaches on this sequence may be feasible. Taken together, the SLiM Ac-EESTSFQGP-CONH2 holds potential as an internal ligand for targeting SHANK1.

Activation of fluoride anion as nucleophile in water with data-guided surfactant selection.

A principal component surfactant_map was developed for 91 commonly accessible surfactants for use in surfactant-enabled organic reactions in water, an important approach for sustainable chemical processes. This map was built using 22 experimental and theoretical descriptors relevant to the physicochemical nature of these surfactant-enabled reactions, and advanced principal component analysis algorithms. It is comprised of all classes of surfactants, i.e. cationic, anionic, zwitterionic and neutral surfactants, including designer surfactants. The value of this surfactant_map was demonstrated in activating simple inorganic fluoride salts as effective nucleophiles in water, with the right surfactant. This led to the rapid development (screening 13-15 surfactants) of two fluorination reactions for ß-bromosulfides and sulfonyl chlorides in water. The latter was demonstrated in generating a sulfonyl fluoride with sufficient purity for direct use in labelling of chymotrypsin, under physiological conditions.

A Boron, Nitrogen, and Oxygen Doped π-Extended Helical Pure Blue Multiresonant Thermally Activated Delayed Fluorescent Emitter for Organic Light Emitting Diodes That Shows Fast kRISC Without the Use of Heavy Atoms.

Narrowband emissive multiresonant thermally activated delayed fluorescence (MR-TADF) emitters are a promising solution to achieve the current industry-targeted color standard, Rec. BT.2020-2, for blue color without using optical filters, aiming for high-efficiency organic light-emitting diodes (OLEDs). However, their long triplet lifetimes, largely affected by their slow reverse intersystem crossing rates, adversely affect device stability. In this study, a helical MR-TADF emitter (f-DOABNA) is designed and synthesized. Owing to its π-delocalized structure, f-DOABNA possesses a small singlet-triplet gap, ΔEST, and displays simultaneously an exceptionally faster reverse intersystem crossing rate constant, kRISC, of up to 2 × 106 s-1 and a very high photoluminescence quantum yield, ΦPL, of over 90% in both solution and doped films. The OLED with f-DOABNA as the emitter achieved a narrow deep-blue emission at 445 nm (full width at half-maximum of 24 nm) associated with Commission Internationale de l'Éclairage (CIE) coordinates of (0.150, 0.041), and showed a high maximum external quantum efficiency, EQEmax, of ≈20%.

Quantitative N- or C-Terminal Labelling of Proteins with Unactivated Peptides by Use of Sortases and a d-Aminopeptidase.

Quantitative and selective labelling of proteins is widely used in both academic and industrial laboratories, and catalytic labelling of proteins using transpeptidases, such as sortases, has proved to be a popular strategy for such selective modification. A major challenge for this class of enzymes is that the majority of procedures require an excess of the labelling reagent or, alternatively, activated substrates rather than simple commercially sourced peptides. We report the use of a coupled enzyme strategy which enables quantitative N- and C-terminal labelling of proteins using unactivated labelling peptides. The use of an aminopeptidase in conjunction with a transpeptidase allows sequence-specific degradation of the peptide by-product, shifting the equilibrium to favor product formation, which greatly enhances the reaction efficiency. Subsequent optimisation of the reaction allows N-terminal labelling of proteins using essentially equimolar ratios of peptide label to protein and C-terminal labelling with only a small excess. Minimizing the amount of substrate required for quantitative labelling has the potential to improve industrial processes and facilitate the use of transpeptidation as a method for protein labelling.

Judicious Heteroatom Doping Produces High-Performance Deep-Blue/Near-UV Multiresonant Thermally Activated Delayed Fluorescence OLEDs.

Two multiresonant thermally activated delayed fluorescence (MR-TADF) emitters are presented and it is shown how further borylation of a deep-blue MR-TADF emitter, DIDOBNA-N, both blueshifts and narrows the emission producing a new near-UV MR-TADF emitter, MesB-DIDOBNA-N, are shown. DIDOBNA-N emits bright blue light (ΦPL = 444 nm, FWHM = 64 nm, ΦPL = 81%, τd = 23 ms, 1.5 wt% in TSPO1). The deep-blue organic light-emitting diode (OLED) based on this twisted MR-TADF compound shows a very high maximum external quantum efficiency (EQEmax ) of 15.3% for a device with CIEy of 0.073. The fused planar MR-TADF emitter, MesB-DIDOBNA-N shows efficient and narrowband near-UV emission (λPL = 402 nm, FWHM = 19 nm, ΦPL = 74.7%, τd = 133 ms, 1.5 wt% in TSPO1). The best OLED with MesB-DIDOBNA-N, doped in a co-host, shows the highest efficiency reported for a near-UV OLED at 16.2%. With a CIEy coordinate of 0.049, this device also shows the bluest EL reported for a MR-TADF OLED to date.

A fluorescent photoaffinity probe for formyl peptide receptor 1 labelling in living cells.

Fluorescent ligands for G-protein coupled receptors (GPCRs) are valuable tools for studying the expression, pharmacology and modulation of these therapeutically important proteins in living cells. Here we report a fluorescent photoaffinity probe for Formyl peptide receptor 1 (FPR1), a critical component of the innate immune response to bacterial infection and a promising target in inflammatory diseases. We demonstrate that the probe binds and covalently crosslinks to FPR1 with good specificity at nanomolar concentrations in living cells and is a useful tool for visualisation and characterisation of this receptor.

Di-Iron(II) [2+2] Helicates of Bis-(Dipyrazolylpyridine) Ligands: The Influence of the Ligand Linker Group on Spin State Properties.

Four bis[2-{pyrazol-1-yl}-6-{pyrazol-3-yl}pyridine] ligands have been synthesized, with butane-1,4-diyl (L1 ), pyrid-2,6-diyl (L2 ), benzene-1,2-dimethylenyl (L3 ) and propane-1,3-diyl (L4 ) linkers between the tridentate metal-binding domains. L1 and L2 form [Fe2 (µ-L)2 ]X4 (X- =BF4 - or ClO4 - ) helicate complexes when treated with the appropriate iron(II) precursor. Solvate crystals of [Fe2 (µ-L1 )2 ][BF4 ]4 exhibit three different helicate conformations, which differ in the torsions of their butanediyl linker groups. The solvates exhibit gradual thermal spin-crossover, with examples of stepwise switching and partial spin-crossover to a low-temperature mixed-spin form. Salts of [Fe2 (µ-L2 )2 ]4+ are high-spin, which reflects their highly twisted iron coordination geometry. The composition and dynamics of assembly structures formed by iron(II) with L1 -L3 vary with the ligand linker group, by mass spectrometry and 1 H NMR spectroscopy. Gas-phase DFT calculations imply the butanediyl linker conformation in [Fe2 (µ-L1 )2 ]4+ influences its spin state properties, but show anomalies attributed to intramolecular electrostatic repulsion between the iron atoms.

A Deep-Blue-Emitting Heteroatom-Doped MR-TADF Nonacene for High-Performance Organic Light-Emitting Diodes.

We present a p- and n-doped nonacene compound, NOBNacene, that represents a rare example of a linearly extended ladder-type multiresonant thermally activated delayed fluorescence (MR-TADF) emitter. This compound shows efficient narrow deep blue emission, with a λPL of 410 nm, full width at half maximum, FWHM, of 38 nm, photoluminescence quantum yield, ΦPL of 71 %, and a delayed lifetime, τd of 1.18 ms in 1.5 wt % TSPO1 thin film. The organic light-emitting diode (OLED) using this compound as the emitter shows a comparable electroluminescence spectrum peaked at 409 nm (FWHM=37 nm) and a maximum external quantum efficiency (EQEmax ) of 8.5 % at Commission Internationale de l'Éclairage (CIE) coordinates of (0.173, 0.055). The EQEmax values were increased to 11.2 % at 3 wt % doping of the emitter within the emissive layer of the device. At this concentration, the electroluminescence spectrum broadened slightly, leading to CIE coordinates of (0.176, 0.068).

Algorithm-driven activity-directed expansion of a series of antibacterial quinazolinones.

Activity-directed synthesis (ADS) is a structure-blind, function driven approach that can drive the discovery of bioactive small molecules. In ADS, arrays of reactions are designed and executed, and the crude product mixtures are then directly screened to identify reactions that yield bioactive products. The design of subsequent reaction arrays is then informed by the hit reactions that are discovered. In this study, algorithms for reaction array design were developed in which the reactions to be executed were selected from a large set of virtual reactions; the reactions were selected on the basis of similarity to reactions known to yield bioactive products. The algorithms were harnessed to design arrays of photoredox-catalysed alkylation reactions whose crude products were then screened for inhibition of growth of S. aureus ATCC29213. It was demonstrated that the approach enabled expansion of a series of antibacterial quinazolinones. It is envisaged that such algorithms could ultimately enable fully autonomous activity-directed molecular discovery.

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells.

We designed and synthesized two new ionic thermally activated delayed fluorescent (TADF) emitters that are charged analogues of a known multiresonant TADF (MR-TADF) compound, DiKTa. The emission of the charged derivatives is red-shifted compared to the parent compound. For instance, DiKTa-OBuIm emits in the green (λPL = 499 nm, 1 wt % in mCP) while DiKTa-DPA-OBuIm emits in the red (λPL = 577 nm, 1 wt % in mCP). In 1 wt % mCP films, both emitters showed good photoluminescence quantum yields of 71% and 61%, and delayed lifetimes of 316.6 µs and 241.7 µs, respectively, for DiKTa-OBuIm and DiKTa-DPA-OBuIm, leading to reverse intersystem crossing rates of 2.85 × 103 s-1 and 3.04 × 103 s-1. Light-emitting electrochemical cells were prepared using both DiKTa-OBuIm and DiKTa-DPA-OBuIm as active emitters showing green (λmax = 534 nm) and red (λmax = 656 nm) emission, respectively.

Two boron atoms versus one: high-performance deep-blue multi-resonance thermally activated delayed fluorescence emitters.

Two new deep-blue narrowband multi-resonant emitters, 1B-DTACrs and 2B-DTACrs, one of which shows thermally activated delayed fluorescence (TADF), based on boron, nitrogen, and oxygen doped nanographenes are reported. Devices based on 2B-DTACrs showed an EQEmax of 14.8% and CIE coordinates of (0.150, 0.044), which are very close to the BT.2020 requirement for blue pixels.

Towards identification of protein-protein interaction stabilizers via inhibitory peptide-fragment hybrids using templated fragment ligation.

Using the hDMX/14-3-3 interaction, acylhydrazone-based ligand-directed fragment ligation was used to identify protein-protein interaction (PPI) inhibitory peptide-fragment hybrids. Separation of the peptide-fragment hybrids into the components yielded fragments that stabilized the hDMX/14-3-3 interaction.

Understanding the interaction of 14-3-3 proteins with hDMX and hDM2: a structural and biophysical study.

p53 plays a critical role in regulating diverse biological processes: DNA repair, cell cycle arrest, apoptosis and senescence. The p53 pathway has therefore served as the focus of multiple drug-discovery efforts. p53 is negatively regulated by hDMX and hDM2; prior studies have identified 14-3-3 proteins as hDMX and hDM2 client proteins. 14-3-3 proteins are adaptor proteins that modulate localization, degradation and interactions of their targets in response to phosphorylation. Thus, 14-3-3 proteins may indirectly modulate the interaction between hDMX or hDM2 and p53 and represent potential targets for modulation of the p53 pathway. In this manuscript, we report on the biophysical and structural characterization of peptide/protein interactions that are representative of the interaction between 14-3-3 and hDMX or hDM2. The data establish that proximal phosphosites spaced ~20-25 residues apart in both hDMX and hDM2 co-operate to facilitate high-affinity 14-3-3 binding and provide structural insight that can be utilized in future stabilizer/inhibitor discovery efforts.

Diindolocarbazole - achieving multiresonant thermally activated delayed fluorescence without the need for acceptor units.

In this work we present a new multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter paradigm, demonstrating that the structure need not require the presence of acceptor atoms. Based on an in silico design, the compound DiICzMes4 possesses a red-shifted emission, enhanced photoluminescence quantum yield, and smaller singlet-triplet energy gap, ΔEST, than the parent indolocarbazole that induces MR-TADF properties. Coupled cluster calculations accurately predict the magnitude of the ΔEST when the optimized singlet and triplet geometries are used. Slow yet optically detectable reverse intersystem crossing contributes to low efficiency in organic light-emitting diodes using DiICzMes4 as the emitter. However, when used as a terminal emitter in combination with a TADF assistant dopant within a hyperfluorescence device architecture, maximum external quantum efficiencies of up to 16.5% were achieved at CIE (0.15, 0.11). This represents one of the bluest hyperfluorescent devices reported to date. Simultaneously, recognising that MR-TADF emitters do not require acceptor atoms reveals an unexplored frontier in materials design, where yet greater performance may yet be discovered.

Computational Mapping of Dirhodium(II) Catalysts.

The chemistry of dirhodium(II) catalysts is highly diverse, and can enable the synthesis of many different molecular classes. A tool to aid in catalyst selection, independent of mechanism and reactivity, would therefore be highly desirable. Here, we describe the development of a database for dirhodium(II) catalysts that is based on the principal component analysis of DFT-calculated parameters capturing their steric and electronic properties. This database maps the relevant catalyst space, and may facilitate exploration of the reactivity landscape for any process catalysed by dirhodium(II) complexes. We have shown that one of the principal components of these catalysts correlates with the outcome (e.g. yield, selectivity) of a transformation used in a molecular discovery project. Furthermore, we envisage that this approach will assist the selection of more effective catalyst screening sets, and, hence, the data-led optimisation of a wide range of rhodium-catalysed transformations.

Pyrene Tags for the Detection of Carbohydrates by Label-Assisted Laser Desorption/Ionisation Mass Spectrometry*.

Matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) is widely used for the analysis of biomolecules. Label-assisted laser desorption/ionisation mass spectrometry (LALDI-MS) is a matrix-free variant of MALDI-MS, in which only analytes covalently attached to a laser desorption/ionisation (LDI) enhancer are detected. LALDI-MS has shown promise in overcoming the limitations of MALDI-MS in terms of sample preparation and MS analysis. In this work, we have developed a series of pyrene-based LDI reagents (LALDI tags) that can be used for labelling and LALDI-MS analysis of reducing carbohydrates from complex (biological) samples without the need for additional chemical derivatisation or purification. We have systematically explored the suitability of four pyrene-based LDI enhancers and three aldehyde-reactive handles, optimised sample preparation, and demonstrated the use of LALDI tags for the detection of lactose. We have also exemplified the potential of LALDI tags for labelling carbohydrates in biological samples by direct detection of lactose in cow's milk. These results demonstrate that LALDI-MS is a promising technique for the analysis of reducing carbohydrates in biological samples, and pave the way for the development of LALDI-MS for glycomics and diagnostics.

Activity-directed expansion of a series of antibacterial agents.

The feasibility of using activity-directed synthesis to drive antibacterial discovery was investigated. An array of 220 Pd-catalysed microscale reactions was executed, and the crude product mixtures were evaluated for activity against Staphylococcus aureus. Scale-up of the hit reactions, purification and evaluation, enabled expansion of a class of antibacterial quinazolinones. The novel antibacterials had MICs from 0.016 µg mL-1 (i.e. 38 nM) to 2-4 µg mL-1 against S. aureus ATCC29213.