Traditional descriptions of the hydrophobic effect on basis entropic arguments or calculation solvent-occupied surfaces must be questioned in view new results obtained with supramolecular complexes. In these studies, it was possible to separate from dispersive interactions, which are strongest aqueous systems. Even very alkanes associate significantly only cavities containing water molecules an insufficient number hydrogen bonds. The replacement high-energy by guest is essential enthalpic...

Molecular dynamics simulations and isothermal titration calorimetry (ITC) experiments with neutral guests illustrate that the release of high-energy water from cavity cucurbit[n]uril (CBn) macrocycles is a major determinant for guest binding in aqueous solutions. The energy individual encapsulated molecules decreases increasing size, because larger cavities allow formation more stable H-bonded networks. Conversely, total internal increases size absolute number increases. For CB7, which has...

The factors affecting host−guest complexation between the molecular container compound cucurbit[6]uril (CB6) and various guests in aqueous solution are studied, a detailed mechanism presence of cations is derived. formation supramolecular complex studied detail for cyclohexylmethylammonium ion as guest. kinetics thermodynamics monitored by NMR function temperature, salt concentration, cation size. binding constants ingression rate decrease with increasing concentration cation-binding...

Cucurbit[n]urils (CB[n]) are potential stabilizing, solubilizing, activating, and delivering agents for drugs. The toxicity of the macrocyclic host molecules cucurbit[7]uril (CB[7]), most water-soluble homologue, as well cucurbit[8]uril (CB[8]) has been evaluated. In vitro studies on cell cultures revealed an IC50 value 0.53 ± 0.02 mM CB[7], corresponding to around 620 mg CB[7] per kg material. Live-cell imaging performed cells treated with subtoxic amounts showed no detrimental effects...

Abstract Cucurbit[ n ]urils (CB ) bind guest molecules through a combination of electrostatic interactions with the carbonyl rims and hydrophobic inner cavity. Investigations solvatochromic probes in CB7 reveal that polarity cavity resembles alcohols (e.g., ‐octanol), while its polarizability ( P =0.12) apparent refractive index D =1.10±0.12) are extremely low, close to gas phase. The calculated molecular quadrupole moments CBs large (Θ zz =−120 −340 Buckingham). A survey reported binding...

ConspectusHost–guest chemistry commenced to a large degree with the work of Pedersen, who in 1967 first reported synthesis crown ethers. The past 45 years have witnessed substantial progress field, from design highly selective host molecules as receptors their application drug delivery and, particularly, analyte sensing. Much effort has been expended on designing and signaling mechanism for detecting compounds biological environmental relevance. Traditionally, chemosensor comprises one...

Abstract Dodecaborate anions of the type B 12 X 2− and 11 Y (X=H, Cl, Br, I Y=OH, SH, NH 3 + , NR ) form strong (K a up to 10 6 L mol −1 for Br inclusion complexes with γ‐cyclodextrin (γ‐CD). The micromolar affinities reached are highest known this native CD. complexation exhibits highly negative enthalpies (up −25 kcal entropies (TΔS −18.4 both ), which position these guests at bottom end well‐known enthalpy‐entropy correlation CDs. high driving force can be traced back chaotropic effect,...

Electron-rich anionic calixarenes and resorcinarenes are known receptors for trimethylammonium-containing neurotransmitters, but the development of practical sensor applications has been impeded by lack suitable supramolecular sensing ensembles as well low selectivity sensitivity macrocyclic cation-receptor hosts. The host–guest complexes between p-sulfonatocalix[n]arenes (n = 4–5) cationic aromatic fluorescent dye lucigenin (LCG) have characterised optical spectroscopic techniques, NMR,...

Abstract Ternary complexes between the macrocyclic host cucurbit[8]uril, dicationic dyes, and chiral aromatic analytes afford strong induced circular dichroism (ICD) signals in near‐UV visible regions. This allows for chirality sensing peptide‐sequence recognition water at low micromolar analyte concentrations. The reversible noncovalent mode of binding ensures an immediate response to concentration changes, which real‐time monitoring chemical reactions. introduced supramolecular method is...

Supramolecular complexation of perylene bis(diimide) (PDI) dyes with the macrocyclic host cucurbit[8]uril (CB[8]) prevents self-aggregation dye molecules and enables their use as highly (photo)chemically stable, strongly-emitting fluorophores in water. The complexes are stimuli-responsive to binders can be electrochemically cycled, leading reversible on–off fluorescence switching access noncovalent formation higher-order architectures Detailed facts importance specialist readers published...

Abstract The membrane translocation of hydrophilic substances constitutes a challenge for their application as therapeutic compounds and labelling probes 1–4 . To remedy this, charged amphiphilic molecules have been classically used carriers 3,5 However, such may cause aggregation non-specific lysis 6,7 Here we show that globular dodecaborate clusters, prominently B 12 Br 2− , can function anionic inorganic broad range cargo (with molecular mass 146–4,500 Da). We cationic neutral peptides,...

Exceptionally stable aqueous dye solutions, resistant towards aggregation as well unspecific adsorption to material surfaces, and with improved photostability, in particular at high levels of irradiation, are obtained when the supramolecular host cucurbit[7]uril (CB7) is added a rhodamine 6G solution. Complexation by CB7 (see picture) increases fluorescence lifetime because low polarizability inside cucurbituril cavity.

The photophysical properties of the phenazine-based dye neutral red were investigated in aqueous solution presence macrocyclic host molecule cucurbit[7]uril (CB7) using ground-state absorption as well steady-state and time-resolved fluorescence measurements. results are contrasted to those previously obtained for β-cyclodextrin (β-CD; Singh et al. J. Phys. Chem. A 2004, 108, 1465). Both (NR) cationic (NRH+) forms formed inclusion complexes with CB7, larger binding constant latter (K = 6.5 ×...

Abstract The potential of cucurbiturils, water-soluble macrocyclic host molecules composed glycoluril units, for tuning the properties fluorescent dyes and advancing new applications is illustrated. Cucurbit[7]uril (CB7), which presents a particularly attractive derivative due to its intermediary size high water solubility, has been shown display variety advantageous effects on dyes, include increased fluorescence intensity brightness, enhanced photostability, protection towards quenchers,...

Controlling the drug supply: UV and NMR spectroscopic studies show that drugs such as omeprazole lansoprazole, popular for treatment of gastric acid related diseases, are stable several weeks by using cucurbit[7]uril a macrocyclic host (see scheme). The also more rapidly converted into their active forms an acid-promoted reaction catalyzed supramolecular pKa shift.

The end-to-end collision frequency of short polypeptides labeled with a fluorescent probe (DBO) at one end and an efficient contact quencher (Trp) the other (see scheme) provides absolute measure time scale conformational changes in structureless peptides as function amino acid type. A general correlation secondary structure propensity applies, most flexible acids being abundant β turns rigid ones sheets.

A factor of 300 enhancement in fluorescence and increased binding is observed when the triphenylmethane dye Brilliant Green binds to bovine serum albumin (BSA) presence macrocyclic host cucurbit[7]uril (CB7) as a supramolecular "enhancer" (see picture). Thus, cumulative (multiplicative) occurs compared effects CB7 alone (factor 6) or BSA 45).

A combination of moderately selective host−guest binding with the impressive specificity enzymatic transformations allows real-time monitoring reactions in a homogeneous solution. The resulting enzyme assays ("supramolecular tandem assays") exploit dynamic fluorescent dye macrocyclic host competition substrate and product. Two examples were investigated: hydrolysis arginine to ornithine catalyzed by arginase oxidation cadaverine 5-aminopentanal diamine oxidase, which substrates have higher...

20 times more rapid is the complexation of organic ammonium ion receptor cucurbit[6]uril (CB6) with cyclohexylmethylamine than cyclohexylmethylammonium species. Within narrow pH region around pKa value amine, kinetics are accelerated but binding constant remains essentially unaffected. In this region, complex formed through amine form followed by fast protonation and not direct form. Molecular dynamics calculations suggest that undergoes a inclusion into CB6 while ingression retarded...