Themed collection Supramolecular Chemistry in Water

This themed collection highlights some of the exciting research in supramolecular chemistry in water.

Cassava (Manihot esculenta Crantz) is a staple food for more than 500 million people, especially in Africa and South America.

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.

Different strategies for obtaining water-soluble cavity-appended metal complexes are described, and their resulting interlocked assets are discussed in relationship with the very specific properties of water as a solvent.

Nanostructured materials, including nanoparticles, nanocomposites, vesicles, and rods, have been prepared by taking advantage of the interesting features of cucurbituril homologues.

A biocompatible fluoride receptor has been developed where the interaction between the boronic acid ester and amine (NH) results in fluoride ion selectivity and enhanced fluorescence quenching.

The bowl-shaped cavity-ligand based on resorcinarene has been successfully transposed into a water-soluble version that readily binds Zn(II) and acetate at physiological pH.

Cucurbiturils inactivate the restriction reaction of type II endonucleases via supramolecular interactions. This was monitored for different enzyme–DNA combinations in the absence and presence of organic macrocycles. The process can be re-activated by competitive displacement on addition of polyamines.

A dynamic covalent crosslinking approach is used to crosslink supramolecular peptide gels.

A DNA-targeting dye exhibited pH-dependent selectivity toward AT-DNA (pH 7) or GC-DNA (pH 5), accompanied by fluorimetric (pH 5) and ICD (pH 7) recognition.

Mesoporous silica nanoparticles loaded with safranin O and capped with disulfide-containing oligo(ethylene glycol) chains were used for the selective and sensitive fluorimetric detection of GSH.

We show that the newly discovered 6 + 6 biotin-formaldehyde macrocycle Biotin[6]uril binds a variety of anionic guest molecules in water. We discuss how and why the anions are bound based on data obtained using NMR spectroscopy, mass spectrometry, isothermal titrations calorimetry (ITC), computational calculations and single crystal X-ray crystallography.

Stereoselectively labelled isotopomers of NAD(P)H are highly relevant for mechanistic studies of enzymes which utilize them as redox equivalents.

Stable dispersions of [60]fullerene in water with concentrations of up to 1.3 mg mL⁻¹ have been obtained using a peptide topological template as the carrier.

We report that, with the increasing length, cell-penetrating poly(disulfide)s preferably accumulate in the endosomes, cytosol and then the nucleoli.

Hydrogelation behavior of a new class of terpyridine based metallogelators are explored. The gelation and the gel morphology was found to be critically dependent on divalent metal ions, anions and on subtle structural changes on the gelator molecule.

A deep cavitand with ionic “feet” dimerizes around hydrophobic compounds in D₂O.

Chelate and mini-chelate effects on sulfate binding was explored for six amide-, amide/amine-, urea-, and urea/amine-based ligands in water-mixed DMSO-d₆. The urea hosts were highly selective for SO₄²⁻, and displayed enhanced binding and greater tolerance for increasing water content as the number of chelate groups increased.

Lanthanide(III) complexes of ‘pseudo’ dipeptide ligands and 3'-pyridine ligands have been characterised as metallo-ribonuclease mimics.

A new class of 2,6-bis(2-anilinoethynyl)pyridine bisureas exhibits selective turn-on fluorescence for chloride in water.

Investigation of charge and pocket depth in a series of receptors led to improved affinity and selectivity for trimethyllysine.

A poly[(2-ethyl-2-oxazoline)-ran-(2-nonyl-2-oxazoline)] random copolymer was synthesized and its thermoresponsive behavior in aqueous solution modulated by the addition of different supramolecular host molecules.

A His-tagged antibody is combined with an NTA-β-sheet breaker and displays a striking increase in Aβ affinity.

Oxidative dimerization of 6^I,6^V-disulfanyl-γ-cyclodextrin yields a duplex tubular structure with internal volume of ∼740 ų allowing formation of very stable inclusion complexes with medium to large organic molecules in water (K_a ∼ 10⁸ M⁻¹).

A zinc calix[6]azacryptand complex was incorporated into dodecylphosphocholine micelles. This complex can strongly and selectively bind linear primary amines in an aqueous medium.

In this article, we use ¹H NMR spectroscopy to study the spontaneous molecular motion of donor–acceptor [2]catenanes in water.

The enantioselectivity of the (E)-cyclooctene produced critically depended on the solvent and also on the phase evolved, maximizing at the flowing/rigid gel border.

Regulating exocytosis of AuNPs by using host–guest interactions between AuNPs and CB[7] molecules.

A novel π-extended Ni^II-porphyrin shows a high selectivity towards human telomeric G-quadruplexes.

The effect of amino acid composition on the formation of transmembrane channels in lipid bilayers upon self-assembly of alt-(L,D)-α-cyclic octapeptides has been investigated.

Uranyl-salophen complexes incorporated into micelles are evaluated as supramolecular nanosystems for the binding of fluoride in water.

A water-soluble metallo-enzyme model featuring a copper(II) site encaged in a closed-shell cavity of a hemicryptophane has been synthesized and studied.

A phosphine-gold(I)-alkynyl-coumarin complex, [Au{7-(prop-2-ine-1-yloxy)-1-benzopyran-2-one}(DAPTA)] (1), was synthesized and the formation of long luminescent fibers in solution was characterized via fluorescence microscopy and dynamic light scattering.

Previously we have demonstrated that host 1 is capable of hydrocarbon gas separation by selective sequestration of butane from a mixture with propane in the headspace above a solution of the host (C. L. D. Gibb, B. C. Gibb, J. Am. Chem. Soc., 2006, 128, 16498–16499).

An amphiphilic meta-ethynylpyridine polymer with chiral amide side chains coordinated with rare-earth metal salts, especially strongly with Sc(III), to stabilise its helical structure with CD enhancement.

Excellent affinities and selectivities toward triphosphates are achieved through an adaptive ditopic receptor featuring a metal ion and a macrocyclic polyammonium cation binding sites, concertedly bridging phosphate anions.

The anion binding and membrane transport properties of a series of cyclic 2,6-bis-(1,2,3-triazolyl)-pyridine receptors with thiourea functionalities are reported.

A variety of luminescent chemosensors is obtained by post-functionalization of self-assembled phospholipid vesicles with receptor units ranging from metal complexes to aptamers.

Bis-scorpiands bind nucleotides in water with 10–100 μM affinity, with selectivity: at pH 7 pyridine-scorpiand toward CMP; at pH 5 phenanthroline-scorpiand toward AMP.

Multi-head/multi-tail facial amphiphiles built on cyclodextrin (CD) and calixarene (CA) scaffolds are paradigmatic examples of monodisperse gene delivery systems.

Four model thiosemicarbazide anion chemosensors containing three N–H bonds, substituted with phenyl and/or 4-nitrophenyl units, were synthesised and studied for their anion binding abilities with hydroxide, fluoride, acetate, dihydrogen phosphate and chloride.

A limited number of modes determine the overall deformations of the macrorings, which may have more than one cavity. Accordingly, they have the potential to accommodate more than one substrate molecule.

A series of straight and branched chain pyrogallol[4]arenes was studied and found to be essentially nontoxic to two strains of E. coli.

An aryl-extended calix[4]pyrrole receptor with four carboxylic groups at the lower rim binds N-oxides in water with high stability constants.

Here a new method to determine the orientation of coiled-coil peptide motifs is described.

A straightforward fluorescence indicator-displacement assay (IDA) has been developed for the quantitative analysis of ATP→ADP conversion.

We report the synthesis of a series of anionic dendritic peptide amphiphiles of increasing hydrophobic character and describe their self-assembly into supramolecular nanorods using pH and ionic strength dependent state diagrams.

Interactions between three hexacationic arene ruthenium metallaprisms and human proteins have been studied using NMR spectroscopy, mass spectrometry and circular dichroism spectroscopy, showing that proteins are potential biological targets for these metallaprisms.

Thermodynamic studies about the interaction of scorpiand aza-macrocycles with amino acids in water show entropy driven stabilisations often associated with solvation/desolvation processes.

The preparation and characterization of a tripeptide based hydrogel, which possesses characteristic rheological properties, is pH responsive and can be functionalized at its thiol function is reported.

The assembly and disassembly of a fluorescent amphiphile by Al³⁺ and citrate, respectively, can be used to sense these analytes by fluorescence spectroscopy.

A multivalent helix mimetic is developed that inhibits the p53/hDM2 and induces dimerization/aggregation of its target – hDM2.

Selectivity of a synthetic anion receptor reverses from strongly coordinating sulfate to weakly coordinating iodide anions upon increasing the water content of the solution.

We describe how modulating the pK_a of a family of synthetic prodigiosenes, modified on their B-ring, can control the transmembrane transport of anions.

Iterative monomer redesign leads to a Kme₃-peptide receptor with 10-fold tighter affinity and 5-fold improved selectivity over Kme₂ than the original receptor. Thermodynamic analysis provides insight into this improvement.

Upper rim diguanidino-cone-calix[4]arenes catalyze the hydrolytic cleavage of diribonucleoside monophosphates in aqueous DMSO with good substrate selectivity and rate accelerations approaching 10⁵-fold in the most favourable substrate-catalyst combinations.

In this study, two types of nanoparticles have been used as additives for the encapsulation of Candida rugosa lipase via the sol–gel method.

Liposomes containing phospholipid-PEG conjugates with terminal zinc(ıı)-bis(dipicolylamine) affinity units selectively target anionic membrane surfaces including the exterior of bacterial and dead/dying mammalian cells.

Insight into structure and stability of B-DNA is obtained through systematic quantum chemical analyses of the roles played by hydrogen bonding, π–π stacking, solvation, and twist-angle.