59 research outputs found
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 MeOHâ:âwater 3â:â2 mixture (0.07âM 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 receptorâs 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 0.07âM) 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 organicâwater mixtures: the powerful synergy of CâH 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 organicâwater solution
A stapled chromogranin A-derived peptide is a potent dual ligand for integrins αvÎČ6 and αvÎČ8
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 αvÎČ6 and αvÎČ8 integrins and is stable in microsomal preparations
Chemical perturbation of oncogenic protein folding: from the prediction of locally unstable structures to the design of disruptors of Hsp90-Client interactions
Protein folding quality control in cells requires the activity of a class of proteins known as molecular chaperones. Heat shock proteinâ90 (Hsp90), a multidomain ATP driven molecular machine, is a prime representative of this family of proteins. Interactions between Hsp90, its coâchaperones, and client proteins have been shown to be important in facilitating the correct folding and activation of clients. Hsp90 levels and functions are elevated in tumor cells. Here, we computationally predict the regions on the native structures of clients câAbl, câSrc, Cdk4, BâRaf and Glucocorticoid Receptor, that have the highest probability of undergoing local unfolding, despite being ordered in their native structures. Such regions represent potential ideal interaction points with the Hsp90âsystem. We synthesize mimics spanning these regions and confirm their interaction with partners of the Hsp90 complex (Hsp90, Cdc37 and Aha1) by Nuclear Magnetic Resonance (NMR). Designed mimics selectively disrupt the association of their respective clients with the Hsp90 machinery, leaving unrelated clients unperturbed and causing apoptosis in cancer cells. Overall, selective targeting of Hsp90 proteinâprotein interactions is achieved without causing indiscriminate degradation of all clients, setting the stage for the development of therapeutics based on specific chaperone:client perturbation
Photochemistry of transition metal complexes (2017â2018)
This chapter reviews the major advances in the field of photochemistry and photocatalysis by transition metal compounds published in 2017â2018. Particular attention has been given to (i) photocatalysis in synthesis (ii) photoreactivity; (iii) biomedical applications of photoactive transition metal complexes, e.g. as photo-CORMs and PDT (photodynamic therapy) agents
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