On-Resin Recognition of Aromatic Oligopeptides and Proteins through Host-Enhanced Heterodimerization

Design and fabrication of fluorous monoliths with tunable surface property for capillary liquid chromatography

Hierarchically porous monoliths with satisfactory properties have been employed in diverse fields, especially separation. In this study, pentafluorophenyl acrylate (PFPA), pentaerythritol tetraacrylate (PETA) and trimethylolpropane tris(3-mercaptopropionate) (TTMP) were selected as precursors to fabricate a novel monolithic column by thermally initiated polymerization in the presence of a binary porogenic system containing tetrahydrofuran and 1-propanol. The fabricated poly(PFPA-co-PETA-co-TTMP) monolithic column revealed excellent permeability and mechanical stability. Additionally, baseline separation of the mixture of small molecules can be achieved, involving alkylbenzene and fluorobenzene in chromatographic assessment, and the theoretical plate number is up to 60,500 plates/m for butylbenzene with a linear velocity of 0.14 mm/s. Tryptic digest of HeLa as an analyte was used to investigate the possibility of the poly(PFPA-co-PETA-co-TTMP) monolith in biological separation by cLC-MS/MS. Moreover, benefiting from the existence of pentafluorophenyl groups, the cucurbit[8]uril (CB[8]) could be modified on the prepared poly(PFPA-co-PETA-co-TTMP) monolith through host-guest interaction to obtain poly(PFPA-co-PETA-co-TTMP)-CB[8] monolith. It could be observed that significant changes in retention behavior of analytes appeared after immobilizing CB[8] on the monolith. It offered an innovative approach by utilizing host-guest interaction to fabricate monolithic columns with different chromatographic behaviors.

Bis(8-hy-droxy-quinolinium) naphthalene-1,5-di-sulfonate tetra-hydrate

The inter-action between 8-hy-droxy-quinoline (8HQ, C9H7NO) and naphthalene-1,5-di-sulfonic acid (H2NDS, C10H8O6S2) in aqueous media results in the formation of the salt hydrate bis-(8-hy-droxy-quinolinium) naphthalene-1,5-di-sulfonate tetra-hydrate, 2C9H8NO+·C10H6O6S2 2-·4H2O. The asymmetric unit comprises one protonated 8HQ+ cation, half of an NDS2- dianion symmetrically disposed around a center of inversion, and two water mol-ecules. Within the crystal structure, these components are organized into chains along the [010] and [10] directions through O-H⋯O and N-H⋯O hydrogen-bonding inter-actions, forming a di-periodic network parallel to (101). Additional stabilizing inter-actions such as C-H⋯O, C-H⋯π, and π-π inter-actions extend this arrangement into a tri-periodic network structure.

Single-Molecule Stoichiometry of Supramolecular Complexes

The use of single-molecule microscopy is introduced as a method to quantify the photophysical properties of supramolecular complexes rapidly at ultra low concentrations (<1 nM), previously inaccessible. Using a model supramolecular system based on the host-guest complexation of cucurbit[n]uril (CB[n]) macrocycles together with a fluorescent guest (Ant910Me), we probe fluorescent CB[n] host-guest complexes in the single molecule regime. We show quantification and differentiation of host-guest photophysics and stoichiometries, both in aqueous media and noninvasively in hydrogel, by thresholding detected photons. This methodology has wide reaching implications in aiding the design of next-generation materials with programmed and controlled properties.

Radical reactions enabled by polyfluoroaryl fragments: photocatalysis and beyond

Polyfluoroarenes have been known for a long time, but they are most often used as fluorinated building blocks for the synthesis of aromatic compounds. At the same time, due to peculiar fluorine effect, they have unique properties that provide applications in various fields ranging from synthesis to materials science. This review summarizes advances in the radical chemistry of polyfluoroarenes, which have become possible mainly with the advent of photocatalysis. Transformations of the fluorinated ring via the C-F bond activation, as well as use of fluoroaryl fragments as activating groups and hydrogen atom transfer agents are discussed. The ability of fluoroarenes to serve as catalysts is also considred.

Adamantylglycine as a high-affinity peptide label for membrane transport monitoring and regulation

The non-canonical amino acid adamantylglycine (Ada) is introduced into peptides to allow high-affinity binding to cucurbit[7]uril (CB7). Introduction of Ada into a cell-penetrating peptide (CPP) sequence had minimal influence on the membrane transport, yet enabled up- and down-regulation of the membrane transport activity.

Cucurbit[8]uril Binds Nonterminal Dipeptide Sites with High Affinity and Induces a Type II β-Turn

In an effort to target polypeptides at nonterminal sites, we screened the binding of the synthetic receptor cucurbit[8]uril (Q8) to a small library of tetrapeptides, each containing a nonterminal dipeptide binding site. The resulting leads were characterized in detail using a combination of isothermal titration calorimetry, 1H NMR spectroscopy, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and X-ray crystallography. The equilibrium dissociation constant values determined for the binding of Q8 to nonterminal dipeptide sites Lys-Phe (KF) and Phe-Lys (FK) were 60 and 86 nm, respectively. These are to the best of our knowledge the highest affinities reported to date for any synthetic receptor targeting a nonterminal site on an unmodified peptide. A 0.79 Å resolution crystal structure was obtained for the complex of Q8 with the peptide Gly-Gly-Leu-Tyr-Gly-Gly-Gly (GGLYGGG) and reveals structural details of the pair-inclusion motif. The molecular basis for recognition is established to be the inclusion of the side chains of Leu and Tyr residues, as well as an extensive network of hydrogen bonds between the peptide backbone, the carbonyl oxygens of Q8, and proximal water molecules. In addition, the crystal structure reveals that Q8 induces a type II β-turn. The sequence-selectivity, high affinity, reversibility, and detailed structural characterization of this system should facilitate the development of applications involving ligand-induced polypeptide folding.

A library of vinyl phosphonate anions dimerize with cyanostars, form supramolecular polymers and undergo statistical sorting

Supramolecular dimers are elementary units allowing the build-up of multi-molecule architectures. New among these are cyanostar-stabilized dimers of phosphate and phosphonate anions. While the anion dimerization at the heart of these assemblies is reliable, the covalent synthesis leading to this class of designer anions serves as a bottleneck in the pathway to supramolecular assemblies. Herein, we demonstrate the reliable synthesis of 14 diverse anionic monomers by Heck coupling between vinyl phosphonic acid and aryl bromide compounds. When this synthesis is combined with reliable anion dimerization, we show formation of supramolecular dimers and polymers by co-assembly with cyanostar macrocycles. The removal of the covalent bottleneck opened up a seamless synthetic route to iterate through three monomers affording the solubility needed to characterize the mechanism of supramolecular polymerization. We also test the idea that the small size of these vinyl phosphonates provide identical dimer stabilities across the library by showing how mixtures of anions undergo statistical (social) self-sorting. We exploit this property by preparing soluble copolymers from the mixing of different monomers. This multi-anion assembly shows the utility of a library for programming properties.