Accelerating supramolecular aggregation by molecular sliding.

Diffusion-based translocation along DNA or RNA molecules is essential for genome regulatory proteins to execute their biological functions. The reduced dimensionality of the searching process makes the proteins bind specific target sites at a "faster-than-diffusion-controlled rate". We herein report a photoresponsive slider-track diffusion system capable of self-assembly rate acceleration, which consists of (-)-camphorsulfonic acid, 4-(4'-n-octoxylphenylazo)benzenesulfonic acid, and isotactic poly(2-vinylpyridine). The protonated pyridine rings act as the footholds for anionic azo sliders to diffusively bind and slide along polycationic tracks via electrostatic interactions. Ultraviolet light triggers the trans to cis isomerization and aggregation of azo sliders, which can be monitored by multiple spectroscopic methods without labeling. The presence of vinyl polymer track increases the aggregation rate of cis azobenzene up to ∼20 times, depending on the stereoregularity of the polymer chain, the acid/base ratio and the addition of salt. This system has a feature of simplicity, monitorability, controllability, and could find applications in designing molecular machines with desired functionalities.

Effect of pendant stereostructure on backbone conformation and enantioseparation ability of helical polyacetylene-based chiral stationary phases.

Six proline-derived acetylene monomers bearing either two stereocenters (S-mR, S-mS, R-mS, Rac-mS and S-mRac) or one stereocenter (S-mBn) were obtained from commercially available N-(tert-butoxycarbonyl)-prolinal. Under the catalysis of Rh-diene complex, they were converted to the corresponding optically active helical polymers, S-pR, S-pS, R-pS, Rac-pS, S-pRac, and S-pBn. The correlations between configuration and position of stereocenters in pendants with the polymer conformation as well as chiral resolution performance were systematically explored by a combination of nuclear magnetic resonance (NMR), Raman, UV-Vis absorption, electronic/vibration circular dichroism spectroscopies, high-performance liquid chromatography (HPLC), and computational simulation. The configuration of the stereocenter adjacent to polymer mainchain determined the sense of helical conformation and the elution order of analytes, while that of the remote one affected the arrangement of pendants and the scope of analytes that could be discriminated. Among 18 aromatic analytes selected, S-pR could discriminate 10, while S-pS recognized 12. The racemization of adjacent or remote stereocenters greatly reduced the scope of analytes that could be resolved. Based on computer simulations, S-pS had larger recognition space than S-pR, favoring the steric fit with the racemates containing axial chirality. The strength and number of intermolecular hydrogen bondings between enantiomers and CSPs predominantly determined the chiral discrimination.

2D Hexagonal Assemblies of Amphiphilic Double-Helical Poly(phenylacetylene) Homopolymers with Enhanced Circularly Polarized Luminescence and Chiral Self-Sorting.

Two-dimensional (2D) chiral materials have been attracting immense attentions owing to their unique properties. Herein, we successfully developed a unique assembly strategy of amphiphilic homopolymers to construct stable free-standing 2D chiral nanosheets in solution. The amphiphilic poly(phenylacetylene) (PPA) homopolymers bearing the hydrophobic and hydrophilic dendritic side chains adopt a DNA-like double-helical conformation. The regular hexagonal nanosheets were formed in THF/EtOH through nucleation and epitaxial growth. The sizes of the nanosheets can be modulated from nanometers to submillimeters upon varying the ratio of binary solvents, while the thickness is linearly correlated with the molecular weights. The 2D architecture can significantly enhance the CPL of polymers with a high dissymmetry factor ≈0.1. Driven by a discrimination of helical conformation, the PPAs can self-sort into homochiral 2D nanosheets, as directly visualized by using fluorescent microscopy.

Light Triggered Co-Assembly of Photocleavable Copolymers and Polyoxometalates with Enhanced Photoluminescence.

A novel co-assembly based on the block copolymer bearing photocleavable groups and macroanionic polyoxometalates Na9 [Ln(W5 O18 )2 ] (LnW10 , Ln = Eu, Dy) triggered by UV light is realized in aqueous solution. The copolymer synthesized by atom transfer radical polymerization (ATRP) undergoes irreversible cleavage upon UV irradiation to generate primary amine (pKa ≈ 8-9) residues which are completely protonated under a neutral pH in aqueous solution. Electrostatic attractions between the resulting positively charged copolymers and anionic LnW10 drive the formation of assemblies. In situ small angle X-ray scattering and transmission electron microscopy are used to characterize the morphology of the assemblies. The microenvironments around polyoxometalates in the core of hybrid assemblies become highly hydrophobic, resulting in dramatically enhanced photoluminescence with the obvious intensity enhancement. The solution parameters pH and salt additives show great effects on the formation of assemblies.

Optically active helical vinylterphenyl polymers: chiral teleinduction in radical polymerization and tunable stereomutation.

Helical vinyl aromatic polymers are emerging as interesting chiral materials due to their dynamic tailorability, synthetic simplicity, and outstanding chemical and physical stabilities. This Personal Account discusses long-range chirality transfer in the radical polymerization of vinylterphenyl monomers and tunable stereomutation of the resultant polymers. It begins with a general introduction to the design, synthesis, and characterization of helical poly{(+)-2,5-bis[4'-((S)-2-methylbutyloxy)phenyl]styrene}, the first one of this series of polymers. Then, long-range chirality transfer during radical polymerization of terphenyl-based vinyl monomers is explained. After that, the chiroptical property control of the resultant polymers by means of the transition from kinetically controlled conformation to thermodynamically controlled conformation and external stimulus is described. This Personal Account concludes by discussing the advantages and disadvantages of the strategy of using vinylterphenyls to obtain optically active helical polymers and providing a short outlook, especially emphasizing the importance of tacticity on the chiroptical properties of polymers.

Dynamic helical cationic polyacetylenes for fast and highly efficient killing of bacteria.

The antimicrobial activity of native antimicrobial peptides (AMPs) is often attributed to their helical structure, but the effectiveness of synthetic mimics with dynamic helical conformations, such as antimicrobial cationic polymers (ACPs), has not been well studied. Herein we demonstrate the antimicrobial activity of pyrrolidinium-pendant polyacetylenes (PAs) with dynamic helical conformations. The PAs exhibit fast and efficient antimicrobial activity against a wide range of pathogens, with low toxicity to mammalian cells and minimal risk of antibiotic resistance. In addition, the full-thickness wound infection model in mice has demonstrated the favorable biocompatibility and effective in vivo antibacterial capabilities of these PAs. Our data suggest that the dynamic helical structure of these PAs allows them to adapt and form pores in the bacterial membrane upon interaction, leading to their potent antimicrobial activity. This work investigated the antibacterial mechanism of dynamic helical ACPs, which provides valuable guidance for the rational design of high-performance antimicrobial agents. STATEMENT OF SIGNIFICANCE: Our study represents a significant contribution to the literature on antimicrobial cationic polymers (ACPs) as alternatives to antibiotics. Through a systematic investigation of the role of dynamic helical conformation in polyacetylenes (PAs) and the use of PAs with adaptive structure for the first time, we have provided valuable insights into the bacterial membrane action and killing mechanisms of these polymers. The results of our study, including fast killing rates and minimum inhibitory concentrations as low as 4-16 µg/mL against a broad range of pathogens and strong in vivo antibacterial activity, demonstrate the potential of these ACPs as high-performance antimicrobials. Our findings may guide the design of future ACPs with enhanced antimicrobial activity.

Thermo-responsive recoverable polymeric inhibitors for the resolution of racemic amino acids.

Novel polymeric inhibitors with lower critical solution temperatures in water were prepared and used to mediate the crystallization of racemic asparagine monohydrate, leading to chiral separation with 88.6 ee%. They could be recollected by simply elevating the temperature with a high yield of around 95% and reused without compromising the stereoselectivity and stability.

Clinical features and treatment status of hemifacial spasm in China.

BACKGROUND: Hemifacial spasm (HFS) is a facial nerve disorder characterized by episodic involuntary ipsilateral facial muscle contraction. Information on Chinese patients with HFS has not been well-characterized. This study aimed to evaluate the clinical feature and the treatment status of HFS across China. METHODS: A cross-sectional study including 1003 primary HFS patients had been carried out in 15 movement disorder clinics in China in 2012. The investigated information was acquired from questionnaires and medical records including demographic data, site of onset, aggravating and relieving factors, treatments prior to the investigation, etc. RESULTS: In this study, the ratio of male to female was 1.0:1.8, the mean age at onset was (46.6 ± 11.5) years. About 1.0% patients were bilaterally affected. The most often site of initial onset was the orbicularis oculi muscle. The most often affected sites were orbicularis oculi, zygomatic, and orbicularis oris muscles. Stress/anxiety and relaxation were most often aggravating and relieving factors, respectively; 2.3% patients had family history, 28.4% cases were combined with hypertension, and 1.4% patients were with trigeminal neuralgia. Botulinum toxin type A (BTX-A) injection was the most commonly used treatment, followed by acupuncture and oral medication. BTX-A maintained the highest repeat treatment ratio (68.7%), while 98.4% patients gave up acupuncture. The mean latency of BTX-A effect was (5.0 ± 4.7) days, the mean total duration of the effect was (19.5 ± 11.7) weeks, and 95.9% patients developed improvements no worse than moderate in both severity and function. The most common side effect was droopy mouth. CONCLUSIONS: The onset age of HFS in China is earlier than that in western countries. The most often used two treatments are BTX-A injection and acupuncture, while the latter kept the poor repeat treatment ratio because of dissatisfactory therapeutic effect.

Solvent effect on the aggregation behavior of rod-coil diblock copolymers.

The water-induced aggregation behavior of rod-coil diblock copolymers based on poly(ethylene oxide) (PEO) and poly{(+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS), PEO104-b-PMBPS53, was investigated in the common solvent THF and in the selective solvent dioxane. Before adding water, PEO104-b-PMBPS53 stayed as single polymer chains no matter what conformation the PEO block took (i.e., either the random coil conformation in THF or the compact globule conformation in dioxane). The critical water content ( approximately 6 wt %) at which PEO104-b-PMBPS53 began to aggregate was also similar in both solvents, indicating that PMBPS dominated the aggregation process. However, the size, the size distribution, and the morphology of aggregates in THF/water were quite different from those in dioxane/water. Narrowly distributed spheres with Rh approximately 20 nm were observed in dioxane, whereas in THF, a bimodal distribution peaked at 3 and approximately 300 nm, was observed. The results from 2D wide-angle X-ray diffraction and polarized optical microscopy demonstrated that the PMBPS blocks packed in a parallel pattern upon aggregation in dioxane/water. The anisotropic disclike structures observed in THF/water also indicated the orientation of the PMBPS blocks upon forming aggregates in dilute solution.