RESUMO
In biology enzyme concentrations are continuously regulated, yet for synthetic catalytic systems such regulatory mechanisms are underdeveloped. We now report how a substrate of a chemical reaction induces the formation of its own catalyst from a dynamic molecular network. After complete conversion of the substrate, the network disassembles the catalyst. These results open up new opportunities for controlling catalysis in synthetic chemical systems.
Assuntos
Técnicas de Química Combinatória/métodos , Biocatálise , Catálise , Teoria de SistemasRESUMO
Making receptors to order: A small dynamic combinatorial library (DCL), formed from two dithiols in water, provides a continuous range of six receptors of different sizes. The majority of the 30 tested amines and ammonium ions amplified receptors from this library, thus spanning the complete receptor-size range and showing that this DCL provides a generic platform for the development of receptors for this important class of compounds.
Assuntos
Aminas/química , Compostos de Amônio/química , Técnicas de Química Combinatória , Catenanos/química , Íons/química , Cinética , Compostos Macrocíclicos/síntese química , Compostos Macrocíclicos/química , Compostos de Sulfidrila/química , Água/químicaRESUMO
Designing synthetic receptors that bind biologically relevant guests in an aqueous solution remains a considerable challenge. We now report a new synthetic receptor for nicotine, selected from a dynamic combinatorial library, that binds this guest in water at neutral pH through a combination of hydrophobic and π-π interactions.
Assuntos
Nicotina/química , Técnicas de Química Combinatória , Concentração de Íons de Hidrogênio , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , TermodinâmicaRESUMO
Counterfeit and/or imitation medicines are becoming a major health problem not only in developing countries but also in wealthier countries. The need of new and easy analytical methods for quality control of drugs is essential. We describe the use of Raman spectroscopy, 1H nuclear magnetic resonance (NMR) and 2D diffusion-ordered spectroscopy (DOSY) NMR to analyse genuine Cialis and seven illegally manufactured formulations of this drug purchased via the internet. Seven out of the eight commercial formulations of tadalafil contain the active ingredient, measured by high performance liquid chromatography (HPLC), within 100+/-5% of stated concentration. Vardenafil and homosildenafil instead of tadalafil were found in the Chinese imitation. 2D DOSY NMR spectra clearly showed similarities and differences in the composition of the pharmaceutical formulations of tadalafil, thus giving a precise and global "signature" of the manufacturer. Our data show that the quality of the Cialis imitations manufactured in India and Syria is correct, whereas the Chinese formulation is adulterated with active pharmaceutical ingredients.
