How Does Solvation Affect the Binding of Hydrophilic Amino Saccharides to Cucurbit[7]uril with Exceptional Anomeric Selectivity?

Cucurbit[7]uril (CB[7]) is known to bind strongly to hydrophilic amino saccharide guests with exceptional α-anomer selectivities under aqueous conditions. Single-crystal X-ray crystallography and computational methods were used to elucidate the reason behind this interesting phenomenon. The crystal structures of protonated galactosamine (GalN) and glucosamine (GluN) complexes confirm the inclusion of α anomers inside CB[7] and disclose the details of the host-guest binding.

Can we beat the biotin-avidin pair?: cucurbit[7]uril-based ultrahigh affinity host-guest complexes and their applications.

The design of synthetic, monovalent host-guest molecular recognition pairs is still challenging and of particular interest to inquire into the limits of the affinity that can be achieved with designed systems. In this regard, cucurbit[7]uril (CB[7]), an important member of the host family cucurbit[n]uril (CB[n], n = 5-8, 10, 14), has attracted much attention because of its ability to form ultra-stable complexes with multiple guests. The strong hydrophobic effect between the host cavity and guests, ion-dipole and dipole-dipole interactions of guests with CB portals helps in cooperative and multiple noncovalent interactions that are essential for realizing such strong complexations.

Coumarine-imino-C2-glucosyl conjugate as receptor for Cu(2+) in blood serum milieu, on silica gel sheet and in Hep G2 cells and the characterization of the species of recognition.

A coumarine-imino-C2-glucosyl conjugate (L) was synthesized and characterized. The conjugate L is found to recognize Cu(2+) in aqueous HEPES buffer by exhibiting a 95% fluorescence quenching in pH range 7-10 even in the presence of several biologically and ecologically relevant metal ions. Fluorescence on-off behavior has been clearly demonstrated on the basis of the binding variability of Cu(2+) to L.

A simple modular aptasensor platform utilizing cucurbit[7]uril and a ferrocene derivative as an ultrastable supramolecular linker.

A simple modular aptamer-based sensor (aptasensor) platform was prepared by combining the merits of the rapid and efficient preparation of a self-assembled monolayer of cucurbit[7]uril (CB[7] SAM) and the strong and specific binding affinity of CB[7] to ferrocenemethylammonium (FA), as an ultrastable supramolecular linker, to immobilize aptamers on CB[7] SAM.

Hydrogen bond energies and cooperativity in substituted calix[n]arenes (n = 4, 5).

Hydrogen-bonded interactions in para-substituted calix[n]arenes (CX[n]) (n = 4, 5) and their thia analogues are analyzed using the recently proposed molecular tailoring approach. The cooperative contribution toward the hydrogen-bonding network within the CX[5] host is shown to be nearly 5 times larger than that in its thia analogue. Hydrogen bond strengths in the O-H···O network are enhanced on substitution of an electron-donating group.

Binding of rhodamine B and kiton red S to cucurbit[7]uril: density functional investigations.

The binding of the laser dyes rhodamine B (RhB) and sulforhodamine B (kiton red S or KRS) to a cucurbit[7]uril (CB[7]) host has been investigated using density functional theory. Both guests (RhB and KRS) contain two N,N-diethylamino groups on a xanthene core. The lowest-energy structure of these host-guest complexes has one of the N,N-diethylamino groups encapsulated within the host cavity, that engenders C-H···O interactions with portals, while the remaining noninteracting diethylamino group resides outside the cavity.

Electronic structure, molecular electrostatic potentials, vibrational spectra in substituted calix[n]arenes (n = 4, 5) from density functional theory.

Electronic structure, molecular electrostatic potential, and vibrational frequencies of para-substituted calix[n]arene CX[n]-R (n = 4, 5; R = H, NH(2), t-Bu, CH(2)Cl, SO(3)H, NO(2)) and their thia analogs (S-CX[n]-R; with R = H and t-Bu) in which sulfur bridges two aromatic rings of CX[n] have been derived from the density functional theory. A rotation around CH(2) groups connecting the phenol rings engenders four, namely, cone, partial cone, 1,2-alternate, and 1,3-alternate CX[n]-R conformers. Of these, the cone conformer comprising of large number of O1-H1···O1' interactions turns out to be of lowest energy.

Electronic structure and normal vibrations in (+)-catechin and (-)-epicatechin encapsulated beta-cyclodextrin.

Host-guest interactions between beta-cyclodextrin (beta-CD) and flavan-3-Ol enantiomers (guest) namely, (+)-catechin (CA) or (-)-epicatechin (EC), have been analyzed within the framework of density functional theory. Both CA and EC consist of two phenol rings, I and II, and a pyran ring, III, which facilitate a variety of binding patterns with the host, beta-CD. The minimum energy beta-CD-CA complex reveals that ring II of CA interacts with primary hydroxyls of the upper rim and the phenol ring I engenders hydrogen-bonded interactions with secondary hydroxyl from the lower rim of CD.