Cytomimetic large-scale vesicle aggregation and fusion based on host-guest interaction

Herein, we have shown a large-scale cell-mimetic (cytomimetic) aggregation process by using cell-sized polymer vesicles as the building blocks and intervesicular host-guest molecular recognition interactions as the driving force. We first prepared the hyperbranched polymer vesicles named branched polymersomes (BPs) around 5-10 μm through the aqueous self-assembly of a hyperbranched multiarm copolymer of HBPO-star-PEO [HBPO = hyperbranched poly(3-ethyl-3-oxetanemethanol); PEO = poly(ethylene oxide)]. Subsequently, adamantane-functionalized BPs (Ada-BPs) or β-cyclodextrin-functionalized BPs (CD-BPs) were prepared through the coassembly of HBPO-star-PEO and Ada-modified HBPO-star-PEO (HBPO-star-PEO-Ada), or of HBPO-star-PEO and CD-modified HBPO-star-PEO (HBPO-star-PEO-CD), respectively. Macroscopic vesicle aggregates were obtained by mixing CD-BPs and Ada-BPs. The intervesicular host-guest recognition interactions between β-CD units in CD-BPs and Ada units in Ada-BPs, which were proved by (1)H nuclear Overhauser effect spectroscopy (NOESY) spectrum and the fluorescence probe method, are responsible for the vesicle aggregation. Additionally, the vesicle fusion events happened frequently in the process of vesicle aggregation, which were certified by double-labeling fluorescent assay, real-time observation, content mixing assay, and component mixing assay.     

A new peptide-based method for the design and synthesis of nanoparticle superstructures: construction of highly ordered gold nanoparticle double helices

Left-handed gold nanoparticle double helices were prepared using a new method that allows simultaneous synthesis and assembly of discrete nanoparticles. This method involves coupling the processes of peptide self-assembly of and peptide-based biomineralization of nanoparticles. In this study, AYSSGAPPMPPF (PEPAu), an oligopeptide with an affinity for gold surfaces, was modified with an aliphatic tail to generate C12-PEPAu. In the presence of buffers and gold salts, amphiphilic C12-PEPAu was used to both control the formation of monodisperse gold nanoparticles and simultaneously direct their assembly into left-handed gold nanoparticle double helices. The gold nanoparticle double helices are highly regular, spatially complex, and they exemplify the utility of this methodology for rationally controlling the topology of nanoparticle superstructures and the stereochemical organization of discrete nanoparticles within these structures.     

Enantioselective capillary gas chromatography on the basis of host-guest interactions with modified cyclodextrins

The use of per-O-alkylated as well as partially alkylated/acylated derivatives of α-, β-, and γ-cyclodextrins as chiral stationary phases has opened many new applications to enantioselective gas chromatography. Chiral recognition is now independent of hydrogen bonding interactions and enantiomer separations are achieved for a large variety of compounds which could not be separated before, including lactones, spiroacetals, alkyl halides, olefins, and even compounds with axial asymmetry.     

Supramolecular host-guest interaction for labeling and detection of cellular biomarkers

Be my guest: A supramolecular host-guest interaction is utilized for highly efficient bioorthogonal labeling of cellular targets. Antibodies labeled with a cyclodextrin host molecule bind to adamantane-labeled magnetofluorescent nanoparticles (see picture) and provide an amplifiable strategy for biomarker detection that can be adapted to different diagnostic techniques such as molecular profiling or magnetic cell sorting.     

Self-diffusion NMR studies of the host-guest interaction between beta-cyclodextrin and alkyltrimethylammonium bromide surfactants

Diffusion measurements by nuclear magnetic resonance (NMR) spectroscopy were used to investigate the host-guest association between beta-cyclodextrin (CD) and alkyltrimethylammonium bromide surfactants with different chain lengths, ranging from 6 up to 16 carbons. The scope and limitations of the method in the study of formation of inclusion complexes are discussed. The influences of the presence of CD in the micellization process have been studied, and the apparent critical micellar concentration and the self-diffusion coefficients of the species present in the systems have been calculated. The stoichiometries of the different complexes have been determined. Evidence for the formation of a 2:1 complex in the case of C(16)TAB has been found.     

Regulation of folding and photochromic reactivity of terarylenes through a host-guest interaction

The photochromic reactivity of terarylenes is integrated with molecular folding that is controlled through a host-guest interaction. A thieno[3,2,b]pyridine unit is introduced into a photochromic terarylene structure as an aryl unit to form a guest-interacting site. Thienopyridine-containing terarylenes showed solvent-dependent photochromic reactivity in solution. A terarylene moiety that contains two thienopyridyl units showed significantly high photocoloration reactivity as high as 88% of photocyclization quantum yield in methanol, whereas that value was only 24% in hexane. A temperature-dependent (1)H NMR spectroscopic study in different solvents indicated an interconversion between photochromic-reactive and unreactive conformations. In methanol, the intermolecular interaction between terarylene species and the solvent molecule slows the rate of interconversion and increases the population of the photochromic-active form, whereas the unreactive conformation is dominant in hexane. Crystal-structural studies demonstrated the perfect regulation of molecular folding between a photochromic-active form and an unreactive conformation by changing the solvents for recrystallization. Single crystals prepared from solutions in methanol showed reversible photochromic reactivity, whereas recrystallization from solutions in hexane did not show this reactivity. X-ray crystallographic studies of single crystals from solutions in methanol demonstrated that the photochromic molecules bind a solvent methanol molecule at the guest-interacting site to regulate the molecular conformation into a photochromic-active form in collaboration with specific intramolecular interactions, whereas crystals from solutions in hexane possess the photochromic-unreactive conformation.     

Conversion of the surface property of oleic acid stabilized silver nanoparticles from hydrophobic to hydrophilic based on host-guest binding interaction

This paper describes a general method to change the surface property of the oleic acid stabilized silver nanoparticles and successful tranferring of the silver nanoparticles from the organic phase into the aqueous phase. By vigorous shaking of a biphasic mixture of the silver organosol protected with oleic acid and p-sulfonated calix[4]arene (pSC4) aqueous solution, it is believed that an inclusion complex is formed between oleic acid molecules and pSC4, and the protective layer of the silver nanoparticles shifts from hydrophobic to hydrophilic in nature, which drives the transfer of silver nanoparticles from the organic phase into the aqueous phase. The efficiency of the phase transfer to the aqueous solution depends on the initial pSC4 concentration. The pSC4-oleic acid inclusion complex stabilized nanoparticles can be stable for long periods of time in aqueous phase under ambient atmospheric conditions. The procedure of phase transfer has been independently verified by UV-vis, transmission electron microscopy, Fourier transform infrared, and 1H nuclear magnetic resonance techniques.     

Advances in the study of the host-guest interaction by using coronene as the guest molecule

This review supplied direct insight of host-guest molecule system by using COR as the guest molecule.     

Aromatic interaction profile to understand the molecular basis of raltegravir resistance

Integrase (IN) is the enzyme of human immunodeficiency virus (HIV) which inserts the viral DNA (vDNA) into the host genome for successful viral replication leading to the infection. However, the chemical basis of HIV IN catalysis is speculative due to lack of complete co-crystal structure. Using the recently published prototype foamy virus IN crystal structure, we developed a model structure of HIV IN showing interaction of vDNA, the metal (Mg²⁺) cofactor, and raltegravir (RLT) in the active site. Molecular docking and dynamics simulations studies showed that RLT uses it core central ring with diketo motif for Mg²⁺ chelation and bridge interaction with DDE motif. The triple arene interactions mediated by RLT with neighboring molecular motifs (Y143, cytosine, and adenine) is maintained during long simulation in wild type (WT). The fluorobenzyl and oxadiazole moieties of RLT forms aromatic stacking with cytosine base (head stacking) aromatic side chain of Y143 (tail stacking), respectively, while central ring further establishes aromatic stacking with distorted adenine base of vDNA (central stacking). The novel triple stacking systems were further explored to understand the molecular basis of drug resistance by molecular simulation. The in silico mutation (N155H, Q148H, and Q148H + G140S) and simulation studies elucidated the structural mechanism of resistance to RLT. The simulation studies provided the molecular basis for interdependency observed for the primary and secondary (Q148H and G140S) mutations and also explained the mechanism of viral fitness regain. Our study reveals that triple stacking and its consequence in terms of VdW energetic profile acts as a critical point to understand the drug-resistance. Here, we demonstrate that the root mean square deviation of centroid system (aromatic stacking) can be used as a major determinant of RLT binding toward the fold resistance. This is first kind of report, which discloses a strategy to explore the molecular level of drug resistance profile using aromatic interactions.     

Construction of dsDNA biosensor based on dendritic SiO2 nanoparticle and investigation on its interaction with benzo[a]pyrene

In this work, a new dsDNA biosensor was constructed to monitor the interaction of DNA and benzo[a]pyrene (BaP). Firstly, dendritic SiO₂ nanoparticles were synthesized by silanization of SiO₂ nanoparticles with (??-(methacryloyloxy)propyl) trimethoxysilane and polymerization with acrylic acid. Then, due to the rich carboxyl groups of these nanoparticles, they were associated with the amino groups of a self-assembly membrane formed on the gold electrode by a sulfur-containing compound, 5-amino-3-mercapto-1,2,4-triazole. Finally, dsDNA was immobilized on the electrode surface by static adsorption with the aid of metallic ion. The whole immobilization steps were characterized by cyclic voltammogram and electrochemical impedance spectrum. After that, using methylene blue as a probe, the interaction of BaP with dsDNA was investigated. A linear relationship between the percentages of current decrease with the logarithm of BaP concentrations was found in the range from 0.33 to 133???M.     

Investigation of the incommensurate and commensurate magnetic superstructures of LiCuVO4 and CuO on the basis of the isotropic spin exchange and classical spin approximations

The spin lattices of magnetic oxides LiCuVO(4) and CuO are made up of CuO(2) ribbon chains. The incommensurate and commensurate magnetic superstructures of these oxides were examined by calculating the total spin exchange interaction energies of their long-range order spin arrangements on the basis of the isotropic spin exchange and classical spin approximations. The incommensurate superstructure (0, 0.532, 0) of LiCuVO(4) was analyzed to find that the next-nearest-neighbor spin exchange interaction J(nnn) is more strongly antiferromagnetic than the nearest-neighbor spin exchange interaction J(nn) in the CuO(2) chains. With this finding, we reassessed the relative strengths of the spin exchange interactions of LiCuVO(4) and CuO and then analyzed the relative energies of their long-range order spin arrangements. The incommensurate superstructure (0, 0.532, 0) of LiCuVO(4) is explained when the J(nn)/J(nnn) ratio is -0.40. Both the incommensurate superstructure (0.506, 0, -0.483) and the commensurate superstructure (0.5, 0, -0.5) of CuO, which occur at 231 and 212.5 K, respectively, are well explained in terms of the calculated total spin exchange interaction energies. The incommensurate superstructure of CuO becomes commensurate by a slight change in one interchain spin exchange interaction, which is due probably to a slight structure change brought about by the temperature lowering.     

Interfacial assembly and host-guest interaction of anthracene-conjugated L-glutamate dendron with cyclodextrin at the air/water interface

The interfacial assembly of photo-induced dimerization of atypical anthracene-containing amphiphilic dendron and host-guest interaction with γ-cyclodextrin has been investigated.It has been proved that even without long alkyl chain the amphiphilic dendron could still form stable Langmuir monolayer at the air/water interface.Through the host-guest interaction,γ-cyclodextrin can be used to encapsulate two headgroups of amphiphilic dendron in the antiparallel direction.However,the formed host-guest complex was sensitive to the surface pressure.Slight compression of surface pressure led amphiphilic dendron to reassemble into nanofibers through the strong π-π stacking between headgroups.On the other hand,under in sitv irradiation,the amphiphilic dendron was stabilized in the cavity of γ-cyclodextrin through headgroup dimerization and the host-guest complex further irregularly aggregated to nanoparticles.Meanwhile,γ-cyclodextrin,as a silencer,blocked the supramolecular chirality transfer.Our conclusion was demonstrated through UV/vis,FT-IR,CD spectrum and AFM images,respectively.     

金纳米粒子的尺寸以及金-二氧化钛相互作用对表面等离激元光催化产氧的影响（英文）

表面等离激元共振效应具有独特的光-物质相互作用的性质,因而近年来被广泛的应用到太阳能转化科学领域.通过调变金属的性质(例如组分、尺寸、形貌等)可以方便地在整个太阳能光谱范围内调节其等离子共振吸收性质,从而有效地增加光催化剂的捕光效率.尽管如此,等离激元光催化目前的能量转化效率仍处于很低的水平,主要是由于光催化剂中的电荷分离以及利用效率很低.理论上可以通过控制优化金属纳米粒子的尺寸以及金属-半导体的相互作用来促进电荷分离及利用效率,从而提高光催化剂的活性.然而,关于金属纳米粒子的尺寸以及金属-半导体的相互作用在表面等离激元光催化剂中的具体作用还亟待详细研究.本文以金/二氧化钛作为典型的表面等离激元光催化剂,通过简便的焙烧后处理可同时实现金粒子尺寸和金-氧化钛界面相互作用的调控.我们发现,催化剂的可见光产氧活性随着焙烧温度呈现火山型关系,其中600 ℃处理的样品表现出最高的活性,在560 nm出的表观量子效率为0.3%,接近甚至超过文献报道的同类结果.随后通过X射线衍射、扫描电镜、光电子能谱、紫外可见光谱等表征手段系统地研究了煅烧温度对于金粒子尺寸和金-氧化钛相互作用的影响.从结果表明,通过不同温度焙烧并未改变二氧化钛自身的性质,且随着温度的升高,金尺寸在600℃之前变化较小,随后突然快速长大.在排除了不同样品的吸光性能的差异后发现,产氧活性随着Au尺寸长大而减少.从光电子能谱的结果发现,金-二氧化钛的界面相互作用随焙烧温度升高而逐步增强.进一步地,通过界面周长的归一化活性得出界面相互作用与产氧活性呈现近似线性关系.最后,通过对光沉积Au样品进行不同温度的煅烧发现大尺寸Au的粒径不随煅烧温度变化,而此时的产氧活性却随焙烧温度增加而增加,这进一步验证了界面相互作用对光催化水氧化的促进作用.综合以上结果可知,最终的等离激元诱导的可见光产氧活性是由尺寸与界面相互作用共同影响的结果,尺寸和界面相互作用的变化会共同影响热电子转移效率和表面反应效率,从而改变整体的光催化产氧效率.     

Construction of mesoscale two-dimensional honeycomb structures:a route from self-assembly building blocks to highly-organized superstructures

正Scientists have devoted great efforts to the construction of nanomaterials with well-ordered superstructures due to their potential applications in various fields,including bioengineering,semiconductors and micro-devices.The self-assembly of various building blocks is a versatile technique for generating the highly-organized superstructures.Recently,the self-assembly of colloids or nanoparticles has become a development frontier of self-assembly,which can lead to superstructures with complexity and functionalities superior to those in the molecular self-assembly[1].     

A core-shell nanoparticle approach to photoreversible fluorescence modulation of a hydrophobic dye in aqueous media

Amphiphilic core-shell nanoparticles containing spiropyran moieties have been prepared in aqueous media. The nanoparticles consist of hydrophilic and biocompatible poly(ethyleneimine) (PEI) chain segments, which serve as the shell, and a hydrophobic copolymer of methyl methacrylate (MMA), a spiropyran-linked methacrylate, and a cross-linker, which forms the core of the nanoparticles. A hydrophobic fluorescent dye based on the nitrobenzoxadiazolyl (NBD) group was introduced into the nanoparticles to form NBD-nanoparticle complexes in water. The nanoparticles not only greatly enhance the fluorescence emission of the hydrophobic dye NBD in aqueous media, probably by accommodating the dye molecules in the interface between the hydrophilic shells and the hydrophobic cores, but also modulate the fluorescence of the dye through intraparticle energy transfer. This biocompatible and photoresponsive nanoparticle complex may find applications in biological areas such as biological diagnosis, imaging, and detection. In addition, this nanoparticle approach will open up possibilities for the fluorescence modulation of other hydrophobic fluorophores in aqueous media.     

Chiroptical switching system based on the host-guest interaction between metal cations and poly(phenylacetylene)s bearing polycarbohydrate ionophore

Polycarbohydrate macromonomers with different degrees of polymerization (DP), that is, end-functionalized (1 → 6)-2,5-anhydro-3,4-di-O-ethyl-d-glucitols with 4-ethynylbenzoyl groups (macromonomer 2: DP = 6.6, and macromonomer 3: DP = 9.5) were synthesized. The copolymerizations of these macromonomers and phenylactylene (PA) were carried out in various molar ratios to give poly(phenylacetylene)s bearing a polycarbohydrate ionophore as the graft chain with various grafting rates, poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y). These polymers showed split-type circular dichroism (CD) spectra in the long absorption region of the conjugated polymer backbones (280-500 nm). This indicated that poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y) had predominantly one-handed helical conformations in the backbones. The CD spectral patterns of these polymers were inverted in the presence of metal cationic guest molecules. On the other hand, control experiments using poly(phenylacetylene)s bearing a monocarbohydrate (poly-(4_x-co-PA_y)) and metal cations did not show such a CD spectral inversion. These results clearly indicated that the chiroptical switching of the poly(phenylacetylene)s bearing polycarbohydrate ionophore was attributable to the host-guest complexation of the polycarbohydrate ionophore with metal cations.     

Attachment of nanoparticles to the AFM tips for direct measurements of interaction between a single nanoparticle and surfaces

Here we report a universal method of attachment/functionalization of tips for atomic force microscope (AFM) with nanoparticles. The particles of interest are glued to the AFM tip with epoxy. While the gluing of micron size particles with epoxy has been known, attachment of nanoparticles was a problem. The suggested method can be used for attachment of virtually any solid nanoparticles. Approximately every other tip prepared with this method has a single nanoparticle terminated apex. We demonstrate the force measurements between a single approximately 50 nm ceria nanoparticle and flat silica surface in aqueous media of different acidity (pH 4-9). Comparing forces measured with larger ceria particles ( approximately 500 nm), we show that the interaction with nanoparticles is qualitatively different from the interaction with larger particles.