Abstract The accumulation of organic micropollutants (OMP) in aquatic systems is a major societal problem that can be addressed by approaches including nanofiltration, flocculation, reverse osmosis and adsorptive methods using insoluble materials (e.g. activated carbon, MOFs, nanocomposites). More recently, polymeric versions of supramolecular hosts (e.g. cyclodextrins, calixarenes, pillararenes) have been investigated as OMP sequestrants. Herein, we report our study of the use of water insoluble dimethylcatechol walled acyclic cucurbit[n]uril (CB[n]) hosts as solid state sequestrants for a panel of five OMPs. A series of hosts ( H1 – H4 ) were synthesized by reaction of glycoluril oligomer (monomer–tetramer) with 3,6‐dimethylcatechol and fully characterized by spectroscopic means and x‐ray crystallography. The solid hosts sequester OMPs from water with removal efficiencies exceeding 90 % in some cases. The removal efficiencies of the new hosts parallel the known molecular recognition properties of analogous water soluble acyclic CB[n]. OMP uptake by solid host occurs rapidly (≈120 seconds). Head‐to‐head comparison with CB[6] in batch‐mode separation and DARCO activated carbon in flow‐through separation mode show that tetramer derived host ( H4) performs very well under identical conditions. The work establishes insoluble acyclic CB[n]‐type receptors as a promising new platform for OMP sequestration.
We present the synthesis and structure-activity relationships of sulfonatocalix[4]arene hosts bearing novel substitutions. The calix[4]arenes are modified on the upper rim at either one or two of the phenolic units, where the dual modifications are introduced regioselectively on neighbouring or opposing phenols. The calix[4]arenes are mono- or di-functionalised with nitro or formyl groups, with the remaining upper-rim sites in all cases occupied by sulphonates. Equilibrium association constants were determined between each host and the guests nicotine, nornicotine, and cotinine. Indicator displacement-based binding studies show that nicotine binds most strongly to the different members of the library followed by nornicotine, whereas cotinine displays weak to no binding. NMR titrations were carried out with nicotine and show different host-guest interaction geometries for the formyl-calix[4]arenes versus the nitro-calix[4]arenes.
Preprint manuscript, including synthesis of new compounds and fluorescence/NMR-based binding data. We present the synthesis and structure-activity relationships of sulfonatocalix[4]arene hosts bearing novel substitutions. The calix[4]arenes are modified on the upper rim at either one or two of the phenolic units, where the dual modifications are introduced selectively on neighboring or opposing phenols. The calix[4]arenes are mono- or di-functionalized with nitro or formyl groups, with the remaining upper-rim sites in all cases occupied by sulfonates. Equilibrium association constants were determined between each host and the guests nicotine, nornicotine, and cotinine. Indicator displacement-based binding studies show that nicotine binds most strongly to the different members of the library followed by nornicotine, whereas cotinine displays weak to no binding. NMR titrations were carried out with nicotine and show different host-guest interaction geometries for the formyl-calix[4]arenes versus the nitro-calix[4]arenes.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
We report a family of highly anionic calixarenes that form discrete homo-dimeric assemblies in pure water, that get stronger in high salt solutions, and that remain assembled in complex, denaturing solutions like real urine. The results reveal the potential of like-charged subunits for self-assembly in high-salt solutions and biological fluids.
The photoopening kinetics has been shown to increase in all the analogues of DHP synthesized
(marginal increase in Br-DHP-CHO). Also, compared to DHP, frormylation decreased the
thermochomism too. Based on this we can isolated either isomers. Compared to BDHP, the
photoopening kinetics has infact increased multiple time, especially Formyl BDHP which has
photoopening rate constant about 8 times that of BDHP. However, there is only marginal
improvement over UV reversal rate.
Unlike benzo group, we cannot attribute the difference in rate caused due to formylation to
increased conjugation and thus increased stability of CPD. The electron withdrawing abilities of
CHO seems to be the plausible cause for the effect. It is well known that presence of electron
withdrawing or donating groups on diene or dienophile affects kinetics of electrocyclization
reaction (or for that matter any pericyclic reaction).
Thus, we may conclude that fomyl group, because of its electron withdrawing effect onDHP
reduces thermochromism can be used in synthesis of better switching DHP analogues.
Post-translational methylation, discovered more than half a century ago, encodes information in the form of a structural modification on a peptide or protein. The addition of a CH3 group is one of the most subtle covalent modifications that exist in biology. In spite of this, recent years have revealed the many profound functional effects that arise from protein methylation in the cell. In an effort to open the doors to new assays and detection methods that would enable new basic and applied research into methylation pathways, chemical agents that can recognise and bind to methylated sites are now being pursued. In this review, we describe the supramolecular approaches to the recognition of methylated amino acids, peptides and proteins that have arisen in the last few years.
Proteome-wide studies of post-translationally methylated species using mass spectrometry are complicated by high sample diversity, competition for ionization among peptides, and mass redundancies. Antibody-based enrichment has powered methylation proteomics until now, but the reliability, pan-specificity, polyclonal nature, and stability of the available pan-specific antibodies are problematic and do not provide a standard, reliable platform for investigators. We have invented an anionic supramolecular host that can form host-guest complexes selectively with methyllysine-containing peptides and used it to create a methylysine-affinity column. The column resolves peptides on the basis of methylation-a feat impossible with a comparable commercial cation-exchange column. A proteolyzed nuclear extract was separated on the methyl-affinity column prior to standard proteomics analysis. This experiment demonstrates that such chemical methyl-affinity columns are capable of enriching and improving the analysis of methyllysine residues from complex protein mixtures. We discuss the importance of this advance in the context of biomolecule-driven enrichment methods.
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