Bistren cryptands and cryptates: versatile receptors for anion inclusion and recognition in water

Bistren cryptands can act as selective anion receptors in water in two distinct versions: as hexaprotonated cages and as dicopper(ii) cryptates. Both classes of receptors exert geometrical selectivity, but dimetallic cryptates establish the strongest interactions with the anion

Recognition and Sensing of Nucleoside Monophosphates by a Dicopper(II) Cryptate

The dicopper complex of a bis-tren cryptand in which the spacer consists of two furane subunits connected in 2,2' by a -CH2- fragment selectively recognizes guanosine monophosphate with respect to other nucleoside monophospates (NMPs) in a MeOH/water solution at pH 7. Recognition is efficiently signaled through the displacement of the indicator 6-carboxyfluorescein bound to the receptor, monitoring its yellow fluorescent emission. Titration experiments evidenced the occurrence of several simultaneous equilibria involving 1:1 and 2:1 receptor/NMP and receptor/indicator complexes. It was demonstrated that the added NMP displaces the indicator from the 2:1 receptor/indicator complex, forming the 1:1 receptor/ analyte inclusion complex. Recognition selectivity is thus ascribed to the nature of nucleotide donor atoms involved in the coordination and their ability to encompass the CuII-CuII distance within the cryptate

Mixing the spacers in azacryptands: effects on halide recognition

Replacement of just one spacer in dicopper cryptates drastically alters the cavity's shape, thus affecting halide recognition

A bistren cryptand with a remote thioether function: Cu(ii) complexation in solution and on the surface of gold nanostars

A di-copper(ii) complex is formed in a bis-tren cage featuring a thioether function, capable of grafting on a monolayer of gold nanostars

Synthesis and Study in Solution of a New Dansyl-Modified Azacryptand

We report the synthesis of a new asymmetric azacryptand (L1), characterized by three p-xylyl spacers, one of which carries a dansyl side arm. The fluorescent sensor has been studied by potentiometric, UV-Vis, and emission studies in MeOH : water 3 : 2 mixture (0.07 M NaNO3), determining, in particular, the protonation constants of the free ligand and metal ion complexation equilibria. Interestingly, the obtained results revealed that the new receptor is fluorescent at neutral pH with a typical emission band of the dansyl group. Metal addition induced a partial quenching of the dansyl emission band; this behavior is more pronounced with Cu(II) that reduces the receptor’s emission by 60%. With all the studied cations, quenching follows the formation of a dimetallic complex. Similar studies on the model compound L2 confirmed that fluorescence quenching is mainly driven by a static mechanism, attributable to the formation of the inclusion dicopper complex [L1Cu2]4+. In order to test the stability of copper complexes under physiological conditions, spectrofluorimetric titrations with Cu(II) were performed in water buffered at pH = 8 (HEPES 0.07 M) and the values of binding constants, K11 and K12, were determined

A Catalytic and Selective Scissoring Molecular Tool for Quadruplex Nucleic Acids

A copper complex embedded in the structure of a water-soluble naphthalene diimide has been designed to bind and cleave G-quadruplex DNA. We describe the properties of this ligand, including its catalytic activity in the generation of ROS. FRET melting, CD, NMR, gel sequencing, and mass spectrometry experiments highlight a unique and unexpected selectivity in cleaving G-quadruplex sequences. This selectivity relies both on the binding affinity and structural features of the targeted G-quadruplexes

Chloride-binding in organic–water mixtures: the powerful synergy of C–H donor groups within a bowl-shaped cavity

2,3,4,5-Tetrafluorobenzyl and imidazolium groups within an open-chain receptor allow for the effective binding of chloride in organic–water solution

Addressing Heterogeneity in Direct Analysis of Extracellular Vesicles and Their Analogs by Membrane Sensing Peptides as Pan‐Vesicular Affinity Probes

: Extracellular vesicles (EVs), crucial mediators of cell-to-cell communication, hold significant diagnostic potential due to their ability to concentrate protein biomarkers in bodily fluids. However, challenges in isolating EVs from biological specimens hinder their widespread use. The preferred strategy involves direct analysis, integrating isolation and analysis solutions, with immunoaffinity methods currently dominating. Yet, the heterogeneous nature of EVs poses challenges, as proposed markers may not be as universally present as thought, raising concerns about biomarker screening reliability. This issue extends to EV-mimics, where conventional methods may lack applicability. Addressing these challenges, the study reports on Membrane Sensing Peptides (MSP) as pan-vesicular affinity ligands for both EVs and their non-canonical analogs, streamlining capture and phenotyping through Single Molecule Array (SiMoA). MSP ligands enable direct analysis of circulating EVs, eliminating the need for prior isolation. Demonstrating clinical translation, MSP technology detects an EV-associated epitope signature in serum and plasma, distinguishing myocardial infarction from stable angina. Additionally, MSP allow analysis of tetraspanin-lacking Red Blood Cell-derived EVs, overcoming limitations associated with antibody-based methods. Overall, the work underlines the value of MSP as complementary tools to antibodies, advancing EV analysis for clinical diagnostics and beyond, and marking the first-ever peptide-based application in SiMoA technology

A stapled chromogranin A-derived peptide is a potent dual ligand for integrins αvβ6 and αvβ8

Combining 2D STD-NMR, computation, biochemical assays and click-chemistry, we have identified a chromogranin-A derived compound (5) that has high affinity and bi-selectivity for αvβ6 and αvβ8 integrins and is stable in microsomal preparations

Particle profiling of EV‐lipoprotein mixtures by AFM nanomechanical imaging

The widely overlapping physicochemical properties of lipoproteins (LPs) and extracellular vesicles (EVs) represents one of the main obstacles for the isolation and characterization of these pervasive biogenic lipid nanoparticles. We herein present the application of an atomic force microscopy (AFM)-based quantitative morphometry assay to the rapid nanomechanical screening of mixed LPs and EVs samples. The method can determine the diameter and the mechanical stiffness of hundreds of individual nanometric objects within few hours. The obtained diameters are in quantitative accord with those measured via cryo-electron microscopy (cryo-EM); the assignment of specific nanomechanical readout to each object enables the simultaneous discrimination of co-isolated EVs and LPs even if they have overlapping size distributions. EVs and all classes of LPs are shown to be characterised by specific combinations of diameter and stiffness, thus making it possible to estimate their relative abundance in EV/LP mixed samples in terms of stoichiometric ratio, surface area and volume. As a side finding, we show how the mechanical behaviour of specific LP classes is correlated to distinctive structural features revealed by cryo-EM. The described approach is label-free, single-step and relatively quick to perform. Importantly, it can be used to analyse samples which prove very challenging to assess with several established techniques due to ensemble-averaging, low sensibility to small particles, or both, thus providing a very useful tool for quickly assessing the purity of EV/LP isolates including plasma- and serum-derived preparations