Differentiating π Interactions by Constructing Concave/Convex Surfaces Using a Bucky Bowl Molecule, Corannulene in Liquid Chromatography

Rational Supramolecular Strategy via Halogen Bonding for Effective Halogen Recognition in Molecular Imprinting

Halogen bonding is a highly directional interaction and a potential tool in functional material design through self-assembly. Herein, we describe two fundamental supramolecular strategies to synthesize molecularly imprinted polymers (MIPs) with halogen bonding-based molecular recognition sites. In the first method, the size of the σ-hole was increased by aromatic fluorine substitution of the template molecule, enhancing the halogen bonding in the supramolecule. The second method involved sandwiching hydrogen atoms of a template molecule between iodo substituents, which suppressed competing hydrogen bonding and enabled multiple recognition patterns, improving the selectivity. The interaction mode between the functional monomer and the templates was elucidated by ¹H NMR, ¹³C NMR, X-ray absorption spectroscopy, and computational simulation. Finally, we succeeded in the effective chromatographic separation of diiodobenzene isomers on the uniformly sized MIPs prepared by multi-step swelling and polymerization. The MIPs selectively recognized halogenated thyroid hormones via halogen bonding and could be applied to screening endocrine disruptors.

An Unrevealed Molecular Function of Corannulene Buckybowl Glycoconjugates in Selective Tumor Annihilation by Targeting the Cancer-Specific Warburg Effect

The biomedical application of corannulene π-bowls is historically limited by low solubility and bioavailability despite the potential in their unique electronic properties for new functional materials. Herein, the unexpected role and molecular mechanism of Corranulene π-bowls are uncovered in biomedical applications as an effective anticancer agent for Warburg effect mediated selective tumor targeting. The corannulene triazolyl monosaccharides Cor-sugars exhibit highly potent cytotoxicity against human cancer cells and effectively inhibit xenograft growth of hyperglycolytic tumors. Particularly, the galactose-conjugated Cor-gal exhibits superior in vivo anticancer efficacy in A549 tumor models with outstanding safety profile compared to doxorubicin. Moreover, the combined treatment of Cor-gal with immune checkpoint inhibitor results in an effective synergy in treating H460 human lung carcinoma. An uptake mechanism study reveals that Cor-sugars exploit tumor-specific glucose transporter glucose transporter 1 (GLUT1) for targeted cell delivery and intra-tumoral accumulation through the cancer-specific Warburg effect. Their significant anticancer activity is attributed to multiphasic DNA-binding and cell cycle alteration effects. This study uncovers new molecular properties of corannulene buckybowl and enabling their potential new applications in biomedical engineering.

Moderate molecular recognitions on ZnO m-plane and their selective capture/release of bio-related phosphoric acids

Herein, we explore the hidden molecular recognition abilities of ZnO nanowires uniformly grown on the inner surface of an open tubular fused silica capillary via liquid chromatography. Chromatographic evaluation revealed that ZnO nanowires showed a stronger intermolecular interaction with phenylphosphoric acid than any other monosubstituted benzene. Furthermore, ZnO nanowires specifically recognized the phosphate groups present in nucleotides even in the aqueous mobile phase, and the intermolecular interaction increased with the number of phosphate groups. This discrimination of phosphate groups in nucleotides was unique to the rich (101̄0) m-plane of ZnO nanowires with a moderate hydrophilicity and negative charge. The discrimination could be evidenced by the changes in the infrared bands of the phosphate groups on nucleotides on ZnO nanowires. Finally, as an application of the molecular recognition, nucleotides were separated by the number of phosphate groups, utilizing optimized gradient elution on ZnO nanowire column. Thus, the present results elucidate the unique and versatile molecular selectivity of well-known ZnO nanostructures for the capture and separation of biomolecules.

Expanding the Analytical Window for Biochar Speciation: Molecular Comparison of Solvent Extraction and Water-Soluble Fractions of Biochar by FT-ICR Mass Spectrometry

Biochar, a low-density yet carbon-rich material derived from different organic materials pyrolyzed under low or no oxygen conditions, has been widely studied as a soil amendment, for greenhouse gas mitigation and in remediation of trace element-contaminated soils. Molecular speciation of biochar compounds has been challenging due to low solubility, aggregation, and immense compositional polydispersity that challenges nearly all mass spectrometry methods routinely applied to carbon-based organic materials. Through a combined technique approach that applies advanced analytical strategies, we provide bulk and molecular characterization of Kentucky bluegrass biochar that can be applied to any biomass or biochar sample. First, we characterize Kentucky bluegrass biochar chemical functional groups by solid-state magic-angle spinning dynamic nuclear polarization NMR (MAS-DNP NMR) and resolve aromatic and aliphatic signals from the pyrogenic material and intact plant material. Next, we isolate water-soluble biochar species by solid-phase extraction followed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and identify highly polar, oxygen species across a wide carbon number range. Solvent fractionation of biochar further expands the compositional range and identifies condensed polycyclic aromatic species across nonpolar and polar classes detected by two ionization modes (-ESI and +APPI) by FT-ICR MS. Plotting biochar species with DBE versus carbon number highlights the pericondensed molecular structural motif that persists across numerous heteroatom classes and ionization modes. To the best of our knowledge, this is the first molecular level identification of nonfunctionalized PAHs in biochar extracts by APPI FT-ICR MS. Thus, we identify biochar species that span the same compositional space as coal, heavy oil asphaltenes, and coal tar and correspond to condensed ring PAHs.

Exploring the Effect of Structure-Based Scaffold Hopping on the Inhibition of Coxsackievirus A24v Transduction by Pentavalent N-Acetylneuraminic Acid Conjugates

Coxsackievirus A24 variant (CVA24v) is the primary causative agent of the highly contagious eye infection designated acute hemorrhagic conjunctivitis (AHC). It is solely responsible for two pandemics and several recurring outbreaks of the disease over the last decades, thus affecting millions of individuals throughout the world. To date, no antiviral agents or vaccines are available for combating this disease, and treatment is mainly supportive. CVA24v utilizes Neu5Ac-containing glycans as attachment receptors facilitating entry into host cells. We have previously reported that pentavalent Neu5Ac conjugates based on a glucose-scaffold inhibit CVA24v infection of human corneal epithelial cells. In this study, we report on the design and synthesis of scaffold-replaced pentavalent Neu5Ac conjugates and their effect on CVA24v cell transduction and the use of cryogenic electron microscopy (cryo-EM) to study the binding of these multivalent conjugates to CVA24v. The results presented here provide insights into the development of Neu5Ac-based inhibitors of CVA24v and, most significantly, the first application of cryo-EM to study the binding of a multivalent ligand to a lectin.

Separation of saccharides using fullerene-bonded silica monolithic columns via π interactions in liquid chromatography

We report on a potential method to separate sugars by using the specific interaction between fullerenes and saccharides in liquid chromatography (LC). Aromatic rings with high electron density are believed to interact strongly with saccharides due to CH–π and/or OH–π interactions. In this study, the fullerene-bonded columns were used to separate saccharides by LC under aqueous conditions. As a result, 2-aminobenzamide-labeled glucose homopolymer (Glcs) was effectively separated by both C60 and C70 columns in the range of Glc-1 to Glc-20 and high blood glucose level being retained in greater quantity. Furthermore, similar separations were identified by LC–mass spectrometry with non-labeled glucose homopolymers. Theoretical study based on molecular dynamics and DFT calculation demonstrated that a supramolecular complex of saccharide–fullerene was formed through CH–π and/or OH–π interactions, and that the interactions between saccharide and fullerene increase with the increase units of the saccharide. Additionally, the C60 column retained disaccharides containing maltose, trehalose, and sucrose. In this case, it was assumed that the retention rates were determined by the difference of the dipole moment in each saccharide. These results suggest that the dipole-induced dipole interaction was dominant, and that maltose—with the higher dipole moment—was more strongly retained compared to other disaccharides having lower dipole moment.

Challenges and Advances in the Fabrication of Monolithic Bioseparation Materials and their Applications in Proteomics Research

High-performance liquid chromatography integrated with tandem mass spectrometry (HPLC-MS/MS) has become a powerful technique for proteomics research. Its performance heavily depends on the separation efficiency of HPLC, which in turn depends on the chromatographic material. As the "heart" of the HPLC system, the chromatographic material is required to achieve excellent column efficiency and fast analysis. Monolithic materials, fabricated as continuous supports with interconnected skeletal structure and flow-through pores, are regarded as an alternative to particle-packed columns. Such materials are featured with easy preparation, fast mass transfer, high porosity, low back pressure, and miniaturization, and are next-generation separation materials for high-throughput proteins and peptides analysis. Herein, the recent progress regarding the fabrication of various monolithic materials is reviewed. Special emphasis is placed on studies of the fabrication of monolithic capillary columns and their applications in separation of biomolecules by capillary liquid chromatography (cLC). The applications of monolithic materials in the digestion, enrichment, and separation of phosphopeptides and glycopeptides from biological samples are also considered. Finally, advances in comprehensive 2D HPLC separations using monolithic columns are also shown.

Separation of halogenated benzenes enabled by investigation of halogen-π interactions with carbon materials

We report the existence of bimodal interactions, the π–π and halogen–π interactions, between the halogenated benzenes and aromatic materials.

The halogen–π (X–π) interaction is an intermolecular interaction between the electron-poor region of bonded halogen atoms and aromatic rings. We report an experimental evaluation of the halogen–π (X–π) interaction using liquid chromatography with carbon-material coated columns providing strong π interactions in the normal phase mode. A C₇₀-fullerene (C70)-coated column showed higher retentions for halogenated benzenes as the number of halogen substitutions increased as a result of X–π interactions. In addition, the strength of the X–π interaction increased in the order of F < Cl < Br < I. Changes to the UV absorption of C70 and the brominated benzenes suggested that the intermolecular interaction changed from the π–π interaction to X–π interaction as the number of bromo substitutions increased. Computer simulations also showed that the difference in dipole moments among structural isomers affected the strength of the π–π interaction. Furthermore, we concluded from small peak shifts in ¹H NMR and from computer simulations that the orbital interaction contributes to the X–π interactions. Finally, we succeeded in the one-pot separation of all isomers of brominated benzenes using the C70-coated column by optimizing the mobile phase conditions.