Electron paramagnetic resonance study of amphiphiles partitioning behavior in desiccation-tolerant moss during dehydration

Desiccation tolerance is a crucial characteristic for desert moss surviving in arid regions. Desiccation procedure always induces amphiphiles transferring from the polar cytoplasm into lipid bodies. The behavior of amphiphiles transferring can contribute to the enhancement of desiccation tolerance and the reduction of plasma membrane integrity simultaneously. The effects of amphiphiles partitioning into the lipid phase during water loss has been studied for pollen and seeds using electron paramagnetic resonance （EPR） spectroscopy. However, desiccation-tolerant high plants occur among mosses, several angiosperms and higher plants seeds or pollens. They have different strategies for survival in dehydration and rehydration. A desiccation-tolerant moss Tortula desertorurn was used to investigate the behaviors of amphiphilic molecules during drying by spin label technology. There are small amount of amphiphilic probes partitioning into membrane during moss leaves dehydration, comparing with that in higher plants. Cytoplasm viscosity changed from 1.14 into glass state only dehydration less than 60 min. Moss leaves lost plasma membrane integrity slightly,from 0.115 to 0.237, occurred simultaneously with amphiphiles partition. The results showed the more advantages of mosses than higher plants in adapting fast dehydration. We propose that EPR spin label is feasible for studying the amphiphiles partitioning mechanisms in membrane protection and damage for desiccation-tolerant mosses.

Molecular Recognition Based on Hydrogen-bonding in the Coliposomes of Phosphatidylcholine and Amphiphiles Using Nucleobases

A functional amphiphile, N^6 -myristoyl-9-[ 8-（ 1-trimethylamino） octyl ] adenine bromide （MTOAB）, was used to form coliposomes of phosphatidyleholine（PC）, PC/thymine, and PC/TOTB using sonication . The morphologies of the coliposomes were characterized using TEM （transmission electron microscopy）. The UV-Vis spectroscopic behavior of PC/MTOAB/thymine （molar ratio = 5： 1： 1 ） and PC/MTOAB/TOTB （molar ratio = 5： 1： 1 ） of coliposomal solutions showed that as a result of base pairing, absorption intensity showed a decrease at 263 nm with increase of time. The decrease of absorption intensity is ascribed to the hypochromic effect, which is because of the formation of hydrogen bonds between adenine and thymine in the coliposomes. The same effect was also observed for the mixture of aqueous PC/MTOAB liposomes and PC/TOTB liposomes after fusion, whereas the nocomplementary coliposomcs formed from PC/MTOAB and PC/TOTB did not show these spectroscopic changes. The molecular recognition through hydrogen interactions between adenine and thymine is very slow because of the possible occurrence of molecular lateral diffusion and exchange of amphiphile before recognition progresses in coliposomes. These results provide useful information for the design of supramolecular devices such as vesicles and liposomes,which can be used to mimic primitive recognition processes observed in biological systems.

Synthesis of Sulfated Cyclodextrin Amphiphiles with Liposomal Encapsulation Properties

A novel class of amphiphiles with sulfate groups at the C-6 position and palmitoyl groups at the C-2, 3 positions of α-, β-, and γ-cyclodextrin (CD) were efficiently synthesized. These compounds formed stable monolayers with high collapse pressures at the air-water interface. The mixed monolayer behaviors of the 6-O-sulfated CD amphiphiles (SO3-CDC16) in the presence of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol were discussed using the surface pressure-molecular area (π-A) isotherms. The collapse pressures showed maxima at molar ratios of SO3-CDC16 lower than 10 mol%. A morphological analysis of the liposomes containing DPPC and 4 mol% SO3-CDC16 formed in PBS was carried out using transmission electron microscopy with negative staining, and vesicles with maximum diameters of 350-500 nm were observed. Moreover, the releasing ability of these liposomes was examined using a fluorescent compound, calcein. It was clearly shown that liposomes containing SO3-CDC16 could release encapsulated calcein more easily than liposomes consisting only of DPPC, and that the release rate depended on the phase transition temperature of the SO3-CDC16 included in the liposome membrane.

Pillar[5]arene-modified peptide-guanidiniocarbonylpyrrol amphiphiles with gene transfection properties

Pillar[5]arene-modified amphiphilic peptides with varying numbers of guanidiniocarbonylpyrrol(GCP)moieties have been successfully synthesized,which can self-assemble to multivalent cationic superstructures in aqueous solutions.These assembled peptides can condense DNA into various compact multimolecular aggregates to achieve successful intracellular DNA delivery and demonstrate great potential for gene transfection.Transfection efficiencies of the self-assembled superstructures have been evaluated in vitro with He La and HEK 293T cells.We demonstrate that GCP moiety could enhance the cell transfection ability,owing to its excellent binding towards cytomembrane.It was also found that subtle structure difference in peptides 2 and 3 could result in distinct transfection efficacy,which makes it possible to gain an in-depth understanding of their structure-activity relationship.This work presents a good example of rational structural design in achieving effective gene transfection vectors.

Self-reporting fluorescence deciphers the antibacterial nature of cationic amphiphiles:Monomer or aggregate?

Cationic amphiphile aggregates exhibit superior antibacterial activity than monomers.However,the antimicrobial mechanism of aggregates has not been well understood because it is difficult to distinguish and monitor aggregate and monomer in antimicrobial process.Herein,three bola-type cationic amphiphiles with aggregation-induced emission property have been developed to show distinguishable fluorescence in their monomer and aggregate.The hydrophilicity of monomer and the stability of aggregate are finely tuned by tailoring the linkers between two quaternary ammonium end groups and tetraphenylethylene skeleton.The sensitive fluorescence switching of monomer and aggregate achieves the quantitative monitoring of dynamic interaction of three amphiphiles with bacteria.The aggregates with cationic charges first attach to bacterial surface,and the monomers subsequently dissociate from aggregates to penetrate bacterial membrane.Further,our results reveal the vital role of stability of aggregates during antimicrobial process,shedding light on the rational design of high-efficient antimicrobials.

Design,Synthesis,and Optical/Electronic Properties of a Series of Sphere-Rod Shape Amphiphiles Based on the C60-oligofluorene Conjugates

A series of sphere-rod shape amphiphiles were designed and synthesized by connecting the rod-like oligofluorenes with different lengths （OF,） to the different positions of the spherical [60]fullerene （C60） through a rigid linkage. The conjugates were characterized by IH-NMR, 13C-NMR, FTIR, EA and MALDI-TOF mass spectrometry. The optical and electronic properties of the conjugates were studied by UV-Vis absorption spectroscopy, fluorescence spectrometry, and cyclic voltammetry. The results from UV-Vis absorption spectroscopy and cyclic voltammetry indicated that the energy profiles of C60 and OFn remained unchanged when different lengths of OFn were attached to C60. The electron affinities of the OFn-C60 conjugates were close to that of C60, while slight electronic interaction was found between the two individual chromophores （C60 and OFn） in their ground states. The fluorescence spectra exhibited a complete fluorescence quenching in the toluene solution, suggesting an effective energy transfer from OFn to C60. It presents a systematic study on the self- assembly, structure-property relationship, and potential technical applications of the conjugates.

Cucurbit[7]uriI-Based Vesicles Formed by Self-assembly of Supramolecular Amphiphiles

Cucurbituril （CB）, a well-known macrocyclic cavitand, has been used extensively to construct supramolecular aggregates. Based on host-guest intertactions, an adamantanyl derivative guest molecule was designed and syn- thesized to prepare a supramolecular amphiphile with cucurbit[7]uril. In aqueous solution, the cucurbit[7]uril based supramolecular amphiphiles self-assemble into well-defined vesicles, and their disassembly can be achieved by addition of excess competitive agent 1-adamantanamine hydrochloride. This vesicle functions as a new nanocapsule to encapsulate molecules within its hollow cavity. Through competitive disassembly of supramolecular amphiphiles, the vesicles behave as a novel drug delivery carrier.

Enhanced stability of nitrogen-doped carbon-supported palladium catalyst for oxidative carbonylation of phenol

Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticles(NPs)on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepared without F127 addition.The hydrogen bond between chitosan(CTS)and F127 was enhanced by F127,which anchored the N in the free amino group,increasing the N content of the carbon material and ensuring that the support could provide sufficient N sites for the deposition of Pd NPs.This process helped to improve metal dispersion.The increased metal-support interaction,which limits the leaching and coarsening of Pd NPs,improves the stability of the Pd/NCF catalyst.Furthermore,density functional theory calculations indicated that pyridine N stabilized the Pd^(2+)species,significantly inhibiting the loss of Pd^(2+)in Pd/NCF during the reaction process.This work provides a promising avenue towards enhancing the stability of nitrogen-doped carbon-supported metal catalysts.

DNA-organic molecular amphiphiles:Synthesis,self-assembly,and hierarchical aggregates

With the development of deoxyribonucleic acid(DNA)nanotechnology,various DNA nanostructures and DNA devices have been constructed,which exhibit potential applications in material science and biomedicine.Taking advantage of the programmability and biocompatibility of DNA,novel building block to chemically functionalize DNA with hydrophobic organic molecules has attracted more and more attention.Driving by amphiphilicity,DNA-organic molecular amphiphiles have been demonstrated to self-assemble or further induce hierarchically assemblies,providing novel-specific properties.In this minireview,we summarize the recent progress of DNA organic molecular amphiphiles including their synthesis,self-assembly behavior in aqueous solution,and the amphiphilic self-assembly based on hierarchical DNA nano-structures.We further briefly discuss the perspective of the application of the DNA-organic molecular amphiphiles.

Construction of Vesicles, Micro/Nanorods and Ultralong Nanotubes through the Self-Assembly of Non-Classical Amphiphiles with Rigid Conformation

Amphiphilic molecules have long been regarded as an important class of supramolecular building blocks for the fabrication of nanomaterials. While most previous researches have mainly focused on amphiphlies with flexible structures, in this work, four novel amphiphiles possessing wholly-rigid skeletons have been designed and synthe- sized. These molecules were built by using 4,4＇-bipyridin-l-ium or viologen as hydrophilic moieties and phenyl or biphenyl as hydrophobic segments, bridged by a pyridazine unit. Their self-assembly behavior has been investigated by scanning electron microscopy （SEM）, atomic force microscopy （AFM） and transmission electron microscopy （TEM）, which revealed they could self-assemble into well-ordered nanoarchitectures with various morphologies such as vesicles, micro/nanorods and nanotubes in water or methanol, depending on their hydrophilic/hydrophobic fraction ratios.

Recent development of pillar[n]arene-based amphiphiles

Pillar[n]arene-based amphiphiles,mainly including amphiphilic pillar[n]arenes and supra-amphiphilic pillar[n]arenes,have obtained considerable interests in recent years due to their fascinating chemical structures,various self-assembly behaviors,and widely applications.Thanks to the pillar-like frameworks and the rich host-guest recognitions of the cavities,these amphiphiles can be easily controlled to form dimensional and morphologic assemblies for multiple applications.Compared with traditional linear covalent amphiphiles,the introduction of host-guest recognitions facilitated the preparation and controllability of these supramolecular amphiphilic systems.Moreover,the host-guest recognitions endow the assemblies from pillar[n]arene-based amphiphiles with stimuli-responsive functions.In this mini-review,we summarized the chemical structures,self-assembly features,and the applications of pillar[n]arene-based amphiphiles.However,several research topics of pillar[n]arenebased amphiphiles can be further developed in the future,such as larger cavity amphiphilic pillar[n]arenes,co-assembly with 2 D materials and utilization of the host-guest interactions.

Fractal Growth of Giant Amphiphiles in Langmuir-Blodgett Films

Fractal structures have attracted considerable scientific interest,and fractal geometry is an effective tool to study the complicated structure and dynamic processes,such as dilation symmetry of disorder structure,percolation,gelation,and metal-insulator transition.Here,we summarized our findings of fractal growth of giant amphiphiles in Langmuir-Blodgett(LB)film.Giant amphiphiles composed of polyhedral oligomeric silsesquioxanes(POSS)derivatives and poly(ethylene oxide)(PEO),with structural diversities of POSS head modification,POSS head number,PEO chain length,are precisely synthesized.The effect of molecular structures and operation parameters on the fractal growth patterns are discussed,in addition,other fractal growth patterns in LB films and in Langmuir films are included,aiming to understand the basic molecular principle of fractal growth in LB system.

Functionalization of Single- and Multi-Walled Carbon Nanotubes with Cationic Amphiphiles for Plasmid DNA Complexation and Transfection

The possibility of delivering DNA effi ciently to cells represents a crucial issue for the treatment of both genetic and acquired diseases.However,even although the effi ciency of non-viral transfection systems has improved in the last decade,none have yet proven to be suffi ciently effective in vivo.We report herein our results on the functionalization of single-walled carbon nanotubes(SWNT)and multi-walled carbon nanotubes(MWNT)by two cationic amphiphiles(lipid RPR120535 and pyrenyl polyamine),their use for the complexation of plasmid DNA,and their efficiency in transfecting cells in vitro.The experiments have shown that the efficiency of transfection is higher when using SWNT instead of MWNT,and that transfection effi ciency is similar or slightly higher when using nanoplexes(SWNT/lipid RPR120535/DNA)instead of lipoplexes(lipid RPR120535/DNA)and several orders of magnitude higher than that of naked DNA.This study therefore shows both that the transfection is better when using SWNTs and that it is dependent on the nature of the amphiphilic molecules adsorbed on the nanotubes.

Mesomorphous structure change by tail chain number in ionic liquid crystalline complexes of linear polymer and amphiphiles

Three polymer-amphiphile complexes were prepared by combining poly（allylamine hydrochloride）（PAH） with the potassium salt of mono-,di-,and trisubstituted benzoic acid dendrons（4-octyloxybenzoic acid,3,5-dioctyloxybenzoic acid,and 3,4,5- trioctyloxybenzoic acid）.The solid structure and properties were monitored with FT-IR,XRD,TG,DSC,and polarized optical microscope（POM）.Difference in the tail chain number of the dendritic amphiphile induced two different mesomorphous structures： lamella for the mono-,disubstituted dendron containing complexes and hexagonal column for the trisubstituted dendron containing complexes.These corresponded to the ionic thermotropic liquid crystal SmA andΦ_h phases,respectively.This finding is significant for design of functional nanostructures based on the ionic complexation of polymers and amphiphiles.

Characterization and phase transition study for vesicles of fluorocarbon amphiphiles with 1,3-disubstituted glycerol structure

This paper presents the preparations and characterization of vesicles of four new fluoro- carbon amphiphiles with 1,3-disubstituted glycerol structure in common and different headgroups (OH, 1; CO_2H, 2; quaternary ammonium salt, 3; and pyridinium salt, 4). These vesicles have higher transition temperature due to the stronger hydrophobic interaction between fluorocarbon chains. Addition of fluorocarbon additives with carboxylic acid or quaternary ammonium salt head group respectively shows different influences on phase behavior of vesicles of 2. These results are discussed based on the interaction within headgroup, hydrophobicity and specific mutahydrophobic interaction between fluoro- and hydrocarbon chains.

Coassembly of Macrocyclic Amphiphiles for Anti-β-Amyloid Therapy of Alzheimer’s Disease

Based on the amyloid hypothesis,anti-β-amyloid(Aβ)therapy has dominated clinical trials for the prevention and treatment of Alzheimer’s disease(AD)in recent years.A key element of this strategy is the interaction between therapeutic agents and Aβ.However,the design and development of artificial receptors that may render selective and strong recognition toward Aβremains a huge challenge because of the complexity and size of peptide guests and their flexible conformation.

Ionic Bent Shape Ternary Facial Amphiphiles

Novel bent shape tenary facial amphiphilic imidazolium ILC which consist of a ^-conjugated bent aromatic cores （2,5-dithiophenylethynyl phenyl bent core）, two terminal poliphilic alkyl chains and lateral n-alky chain terminated by an imidazolium bromide unit were synthesized by using Kumada and Sonogashira coupling reactions as key steps and both their thermotropic and lyotropic mesophase behaviors were studied by POM, DSC and XRD. Columnar phases were found in these compounds, a hexagonal cylinder model with core shell structure is supposed for the columnar phase formed by compound 1/8. Our study may provide a new strategy for designing new LC functional material.

Phase Behavior of Amphiphiles at Liquid Crystals/Water Interface: A Coarse-grained Molecular Dynamics Study

We present a coarse-grained molecular dynamics simulation study of phase behavior of amphiphilic monolayers at the liquid crystal （LC）/water interface. The results revealed that LCs at interface can influence the lateral ordering of amphiphiles. Particularly, the amphiphile tails along with perpendicularly penetrated LCs between tails undergo a two-dimension phase transition from liquid-expanded into a liquid-condensed phase as their area density at interface reaches 0.93. While, the liquid-condensed phase of the monolayer never appears at oil/water interface with isotropic shape oil particles. These findings reveal the penetration of anisotropic LC can promote ordered lateral organization of amphiphiles. Moreover, we find the phase transition point is shifted to lower surface coverage of amphiphiles when the LCs have larger affinity to the amphiphile tails.

Constituent Isomerism-Induced Quasicrystal and Frank-KasperσSuperlattices Based on Nanosized Shape Amphiphiles

Naturally,subtle variations in the chemical structures of constituent molecules may significantly affect their multiscale spatial arrangements,properties,and functions.Deceptively simple spherical assemblies supply an ideal platform to investigate how subtle chemical differences affect hierarchically assembled structures.Here,the authors report two sets of nanosized shape amphiphiles,which were constructed by a triphenylene core and six polyhedral oligomeric silsesquioxane cages peripherally grafted through linkers.The slight differences in these samples are merely several methylene units in their linkers,including several pairs of constituent isomers.These nanosized shape amphiphiles self-assemble into a variety of unconventional spherical packing structures,which include the Frank-Kasperσphase and dodecagonal quasicrystal.Several types of unconventional phase transitions were systematically investigated.The authors alternated the conventional columnar phases of discotic molecules to unconventional spherical packing phases.These unconventional structures may shed light into discovering discotic mesogens-based materials with new properties and functions.

Elimination of Surfactants and Small Dyes from Water with Silicasupported Dendritic Amphiphiles

Silica-supported branched polyethylenimine（Sil@PEI） is a conventional adsorbent and shows a limited affinity to anionic surfactants and small dyes（K = 106？107 L/mol）. If the PEI is alkylated with cetyl groups（C16）, the K of the resulting adsorbents（Sil@PEI@C16-x, where x is the fraction of PEI units being alkylated） is significantly improved. Optimization shows that Sil@PEI@C16-0.15 can best reduce aqueous surfactants to a residue around 10？10 mol/L; while Sil@PEI@C16-0.6 can reduce even small aqueous dyes to a residue below 10？10 mol/L, nearly 105-fold lower than that by Sil@PEI. The adsorbents are well recyclable. It is believed that in the case of dyes, the dense cetyl shell can isolate the PEI from the bulky water and thus suppress the competitive binding by water; while in the case of surfactants, the semiclosed cetyl shell can simultaneously meet electrostatic complement and hydrophobic complement to the surfactants.