Chan-Lam Reaction and Lewis Acid Promoted 1,3-Rearrangement of N-O Bonds to Prepare N-(2-Hydroxyaryl)pyridin-2-ones.

We describe the difunctionalization of arylboronic acids to prepare various N-(2-hydroxyaryl)pyridin-2-ones in good yields using N-hydroxypyridin-2-ones as the oxygen and nitrogen sources through a copper(II)-catalyzed Chan-Lam reaction and subsequent BF3-promoted selective 1,3-rearrangement of N-O bond in a one-pot procedure. Mechanistic studies reveal that the 1,3-rearrangement selectivity is controlled by the formation of the key aryloxypyridinium salt. The obtained products are easily converted to various useful pyridin-2-one scaffolds.

Radical alkylation of para-quinone methides with 4-substituted Hantzsch esters/nitriles via organic photoredox catalysis.

A novel photocatalytic protocol is herein described for the preparation of functionalized phenols via radical alkylation of para-quinone methides under transition-metal-free conditions. The reaction is external oxidant free and performed at ambient temperature upon visible light irradiation, allowing the access to various desired products in satisfactory yields. The readily available 4-alkyl-1,4-dihydropyridines serve as the effective alkyl radical precursors.

Diverse Transformation of Vinyl Azides with 2,2,6,6-Tetramethyl- N-oxopiperidinium.

A 2,2,6,6-tetramethyl- N-oxopiperidinium (TEMPO+)-mediated three-component diverse transformation of vinyl azides under metal-free conditions is described. The reaction protocols are operationally simple and conducted at ambient temperature, allowing to access various TEMPO-trapped ketones, amides, and α-alkoxyalkyl azides. Preliminary mechanistic studies indicate that an alkene radical cation-mediated radical-radical cross-coupling C-O bond formation could be involved.

Modeling the Self-Assembly of Bolaamphiphiles under Nanoconfinement by Coarse-Grained Molecular Dynamics.

Novel and complex nanostructures of amphiphiles assemblies facilitate realizing of many practical applications in nanotechnologies. Under different physical conditions, amphiphiles can form various morphologies. In this article, the self-assembly of bolaamphiphiles was investigated under the cylindrical confinement of carbon nanotubes by coarse-grained molecular dynamics simulation. We found that bolaamphiphiles inside a carbon nanotube with a relatively large diameter tended to self-assemble into curved cylindrical micelles, and further some of these micelles can form double helix structures which were not observed in bulk solutions. We develop an effective method to characterize different morphologies. Our analysis results showed that the formation of double helix and other amorphous morphologies of micelles in carbon nanotubes is not induced by the conformational variation of bolaamphiphiles. Moreover, through examining the potential energies of different structures, we infer that it is entropy which leads micelles to bend even to form double stranded helix structures. In addition, we analyzed the sizes of micelles and find the scission and recombination of micelles during the double helix formation process. This work indicates that the confinement of carbon nanotube is an available method to produce complex nanostructures and provides some new insights of the self-assembly of bolaamphiphiles.

Effect of hydrophobic mismatch on domain formation and peptide sorting in the multicomponent lipid bilayers in the presence of immobilized peptides.

In the plasma membranes, many transmembrane (TM) proteins/peptides are anchored to the underlying cytoskeleton and/or the extracellular matrix. The lateral diffusion and the tilt of these proteins/peptides may be greatly restricted by the anchoring. Here, using the coarse-grained molecular dynamics simulation, we investigated the domain formation and peptide sorting in the ternary lipid bilayers in the presence of the immobilized peptide-grid and peptide-cluster. We mainly focused on examining the combining effect of the peptide immobilization and hydrophobic mismatch on the domain formation and peptide sorting in the lipid bilayers. Compared to the lipid bilayers inserted with free TM peptides, our results showed that, because of the tilt restriction imposed on the peptides, the hydrophobic mismatch effect more significantly influences the domain size, the dynamics of domain formation, and the peptide sorting in our systems. Our results provide some theoretical insights into understanding the formation of nanosized lipid rafts, the protein sorting in the lipid rafts and the interaction between the cytoskeleton, the extracellular matrix, and the plasma membranes.

1-Quasiconformal mappings and CR mappings on Goursat groups.

We show that 1-quasiconformal mappings on Goursat groups are CR or anti-CR mappings. This can reduce the determination of 1-quasiconformal mappings to the determination of CR automorphisms of CR manifolds, which is a fundamental problem in the theory of several complex variables.

Interplay between curvature and lateral organization of lipids and peptides/proteins in model membranes.

Membrane curvature plays a crucial role in the realization of many cellular membrane functions such as signaling and trafficking. Here, using coarse-grained molecular dynamics (MD) simulation, we present an effective method of producing curved model membranes and systematically investigated the interplay between the curvature and lateral sorting of lipids and transmembrane (TM) peptides/proteins in the model membranes. We first confirmed the experimental results of the lateral organization of lipid domains in curved ternary membranes. Then, we focused on exploring the lateral sorting of TM peptides/proteins with symmetric shape in the curved membranes. The results showed that the lateral inhomogeneous packing of lipids induced by the curvature and/or the component heterogeneity drives the peptides/proteins to accumulate in the curved regions in both the unary and ternary membranes. However, whether the peptides/proteins can stably and compactly reside in the curved regions is determined by their final packing configuration, which may be influenced by the membrane curvature in the curved regions. Additionally, the insertion of peptides/proteins may enhance the membrane curvature. This work provided some theoretical insights into understanding the mechanism of the interplay of membrane curvature and lateral organization (especially the lateral sorting of the peptides/proteins with symmetric shape) in the biomembrane in some biological processes.