A new approach towards the rapid identification of quality binders to cucurbiturils--those that combine high affinity with high selectivity for a particular homologue--was developed. The assay exploits macrocycle-specific optical fingerprints (colorimetric or fluorimetric) of carefully selected indicators dyes. The screening of a guest library revealed known (e.g., adamantane derivatives) and new (e.g., terpenes) quality binders. The predictive power of the assay was underpinned by the modeling of the involved thermodynamic equilibria.
Hydrogen sulfide (H2S) has become an important target for research due to its physiological properties as well as its potential applications in medicine. In this work, supramolecular binding of sulfide (S2-) and hydrosulfide (HS-) anions in water is presented for the first time. Bambusurils were used to slow down the release of these anions in water.
A method for the phototriggered release of a biogenic amine from the host-guest complex with the cucurbit[7]uril macrocycle in aqueous solution was devised. The approach exploits a photoinduced pH jump from 8 to 5, combined with the pH-dependent switching of the competitive capacity of a guest dye. The fluorescence fingerprint of the competitor can be used to monitor the amine release in the micromolar concentration regime.
Inappropriate farming techniques and 4 years of drought (1992)(1993)(1994)(1995) produced conditions for high nitrate concentration in an aquifer located in the Province of Seville (Southwest Spain). The objectives of this study were to study groundwater components and to determine the relationship between the cropping system and nitrate concentrations in groundwater. From October 1994 to May 1996, 16 groundwater samples were obtained from a network of 35 sample points. Groundwater concentrations were analysed by multivariate statistical techniques (factor and cluster analysis). Two factors were found: firstly, agricultural pollution and secondly, salinization (from natural mineralization of groundwater and from anthropogenic effects). High levels of NO − 3 were closely associated with intensive cotton (Gossypium herbaceum L.) and potato production (Solanum tuberosum L.). The salinization factor includes electrical conductivity, Cl − , Na + , Ca 2+ , Mg 2+ , SO 2− 4 and HCO − 3 . Our study permits the impact of crops on groundwater to be determined. In comparison to the other crops, cotton (Gossypium herbaceum L.) and potato (Solanum tuberosum L.) made the greatest contribution to nitrate pollution and salinization. Use of the groundwater for human consumption in drought periods could represent a public health risk. Alternative farming techniques for these crops such as monitored fractional fertilization and controlled irrigation are recommended.
Dicyanoaurate(I) anion, [Au(CN) 2 ] À , plays a central role in the current industrial production of gold, as its extraction from crude ore samples represents the most money-consuming step. Herein, we present the strongest host-guest recognition of dicyanoaurate anion using the bambusuril receptor in water, a highly competitive solvent. The micromolar stability of such a complex facilitated the up to date most efficient supramolecular stripping of dicyanoaurate from activated carbon at ambient temperature. Thermodynamic characteristics of bambusuril binding with [Au(CN) 2 ] À differing from binding of other inorganic chaotropic anions are rationalized, as well as the bambusuril selectivity for [Au(CN) 2 ] À over [Ag(CN) 2 ] À .
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