Supramolecularly regulated artificial transmembrane signal transduction for 'ON/OFF'-switchable enzyme catalysis.

An artificial signal transduction model with a supramolecular recognition headgroup, a membrane anchoring group, and a pro-enzyme catalysis endgroup was constructed. The transmembrane translocation of the transducer can be reversibly regulated by competitive host-guest complexations as an input signal to control an enzyme reaction inside the lipid vesicles.

semiaza-Bambusurils are anion-specific transmembrane transporters.

semiaza-Bambus[6]urils efficiently transport anions across lipid membranes. A systematic modification of their lipophilic side chains to include various alkyl groups and thioethers reveals that the most efficient chloride transporters are those that agree with Lipinski's rule-of-lipophilicity, exhibiting clog Po/w values close to 5. Furthermore, vesicle anion-transport assays show that the new anion-transporters are independent of the cation identity but exhibit high anion selectivity, NO3- > Br- > Cl- > SO42-, in agreement with the Hofmeister series. These findings will allow for the design of highly specific anion transporters for biomedical applications, particularly for managing anion channelopathies.

Spread of respiratory infections in student dormitories in China.

OBJECTIVES: Student dormitory rooms in China are characterized by small space and high occupancy. This study aims to investigate infection rates for common colds and influenza among college students in a Chinese university and their association with the dormitory environment. METHODS: This study involved two phases. In Phase I, 2978 students living in 998 dorm rooms in 12 buildings responded to a questionnaire survey on infections in four seasons. In Phase II, based on the data obtained from the questionnaire survey, we selected 242 dorm rooms to measure air temperature, relative humidity and CO2 concentration in both summer and winter. Ventilation rates at night were calculated based on measured CO2 concentrations. RESULTS: We found that students had infections more often in winter, and in rooms with higher occupancy and dampness problems. The median value of the ventilation rate in dorm rooms in summer was 10.7 L/s per person, while it was 4.10 L/s per person in winter. There were significant associations between ventilation rate per person at night and common cold and influenza both in summer and winter (p < 0.05). A combination of dampness and low ventilation rate significantly increased the risk of common colds (adjusted odds ratios, AOR: 1.26-1.91) and influenza (AOR: 1.49-2.20). CONCLUSION: College students living in a crowded dormitory room with low ventilation and dampness problems had more common colds and influenza infections.

Hybrid Helical Polymer Nanochannels Constructed by Combining Aromatic Amide and Pyridine-Oxadiazole Structural Sequences.

An effective method is reported to synthesize aromatic helical polymer nanochannels by combining both the well-studied aromatic amide helical codons with pyridine-oxadiazole helical codons into helical structure sequences. With this strategy, a type of helical polymer nanochannel that shows structure-directed transmembrane transport functions is synthesized. Although such nanochannels show relatively weak selectivity for the transportation of alkali metal ions, accessible chemical mutation of helical structure sequences will provide a great chance for the design of desired channel property. The straightforward preparation of well-established pyridine-oxadiazole helical structure will significantly promote the synthesis of this kind of aromatic helical polymer nanochannels. With the development of aromatic amide foldamers, moreover, a number of "monomers" will be available for the preparation of helical polymer nanochannels.

Morphological Transformation between Orthogonal Dynamic Covalent Self-Assembly of Imine-Boroxine Hybrid Polymer Nanocapsules and Thin Films via Linker Exchange.

Orthogonal dynamic covalent self-assembly is used as a facile method for constructing polymer hollow nanocapsules (NCs) and thin films. The bifunctional precursor 4-formylphenylboronic acid is symmetrically installed with a boronic acid group for the boroxine linkage, and an aldehyde group for the Schiff base reaction which can react with twofold symmetry linkers ethylenediamine and para phenylenediamine to attain polymer NCs and nanosheets. Owing to the reversibility of the imine linkages, the mutual morphological transformation between polymer NCs and thin films via an amine-imine-exchange strategy is successfully achieved. Multiple reversible covalent bonds allow the control the release of the load in polymer NCs using different techniques. This may be useful for designing stimulus-responsive smart materials.

Access to Benzoxazepines and Fully Substituted Indoles via HDDA Coupling.

The HDDA-derived benzyne intermediate was captured by oxazolines based on the addition reaction of benzyne to the C═N double bond. Benzoxazepine derivatives, fused benzoxazepine derivatives, and fully substituted indoles are synthesized in one step. The reaction does not require any catalyst or additives. Possible reaction mechanisms are presented.

Supramolecular nanochannels self-assembled by helical pyridine-pyridazine oligomers.

Herein, we demonstrate a supramolecular nanochannel formed by intermolecular π stacking of pyridine-pyridazine helical oligomers, wherein alkali ions could be easily recognized and transported. Importantly, this nanochannel also revealed reversible collection and triggered-release behaviors via modulating the folded and unfolded states of helical pyridine-pyridazine oligomers.

Template-Free Construction of Highly Ordered Monolayered Fluorescent Protein Nanosheets: A Bioinspired Artificial Light-Harvesting System.

Using biological materials for light-harvesting applications has attracted considerable attention in recent years. Such materials provide excellent environmental compatibility and often exhibit superior properties over synthetic materials. Herein, inspired by the outstanding energy transfer performance in coelenterates, we constructed a template-free, highly ordered two-dimensional light-harvesting system by covalent-induced coassembly of EBFP2 (donor) and EGFP (acceptor), in which the fluorescent chromophores were well distributed and adopted a fixed orientation. By introducing approximate square planar binding sites on the side surface of protein, assembly pattern was pin down and self-assembly extended in orthogonal directions to achieve monolayered and tessellated protein nanoarrays. The excellent antiself-quenching property of fluorescent proteins endowed the coassembled system with attractive light-harvesting capability. Even at high local concentrations, a low resonance energy transfer self-quenching was observed and, therefore, energy can be efficiently transferred. More importantly, the distance between adjacent chromophores is continuously adjustable. By making minor changes to the length of the inducing linker, we have achieved significant control over the size of the assembly. A micron-sized light-harvesting system with satisfactory energy transfer efficiency was finally obtained. This work developed a template-free light-harvesting system completely based on fluorescent proteins (FPs), which overcame the restriction of using templates. Not limited to this work, the special core-shell structure of FPs may be expected to direct the optimization of fluorescent dyes by cladding.

Highly Selective Artificial Potassium Ion Channels Constructed from Pore-Containing Helical Oligomers.

Potassium ion channels specifically transport K+ ions over Na+ ions across a cell membrane. A queue of four binding sites in the K+ channel pore plays significant roles during highly selective conduction. A kind of aromatic helical oligomer was synthesized that can selectively bind K+ over Na+ . By aromatic stacking of helical oligomers, a type of artificial K+ channels with contiguous K+ binding sites was constructed. Such artificial channels exhibited exceptionally high K+ /Na+ selectivity ratios during transmembrane ion conduction.

Semithiobambus[6]uril is a transmembrane anion transporter.

Semithiobambus[6]uril is shown to be an efficient transmembrane anion transporter. Although all bambusuril analogs (having either O, S or N atoms in their portals) are excellent anion binders, only the sulfur analog is also an effective anion transporter capable of polarizing lipid membranes through selective anion uniport. This notable divergence reflects significant differences in the lipophilic character of the bambusuril analogs.

Biomimetic Transmembrane Channels with High Stability and Transporting Efficiency from Helically Folded Macromolecules.

Membrane channels span the cellular lipid bilayers to transport ions and molecules into cells with sophisticated properties including high efficiency and selectivity. It is of particular biological importance in developing biomimetic transmembrane channels with unique functions by means of chemically synthetic strategies. An artificial unimolecular transmembrane channel using pore-containing helical macromolecules is reported. The self-folding, shape-persistent, pore-containing helical macromolecules are able to span the lipid bilayer, and thus result in extraordinary channel stability and high transporting efficiency for protons and cations. The lifetime of this artificial unimolecular channel in the lipid bilayer membrane is impressively long, rivaling those of natural protein channels. Natural channel mimics designed by helically folded polymeric scaffolds will display robust and versatile transport-related properties at single-molecule level.