Multivalent fertilinbeta oligopeptides: the dependence of fertilization inhibition on length and density

The sperm protein fertilinbeta, a member of the ADAM family of proteins, is implicated in sperm-egg binding in all mammals studied to date. Multivalent inhibitors containing the three amino acid binding sequence of fertilinbeta, ECD, have been shown previously to be more effective inhibitors of fertilization than their monovalent counterparts. Here, we probed sperm-egg interactions with ruthenium-catalyzed ring-opening metathesis polymers that contained from 3 to 70 ECD pharmacophores in densities ranging from 10% to 100%. Evaluation of the polymer potencies, and synthesis of a triblock copolymer from two building blocks, revealed that two multivalent contacts are sufficient for maximal inhibition, and that the distance between ECD pharmacophores required is 7-9 monomers spanning 4-5 nm. We conclude that inhibition requires recruitment of two receptors on the egg surface into an inhibitory complex.     

Multivalent gold glycoclusters: high affinity molecular recognition by bacterial lectin PA-IL

Multivalent protein-carbohydrate interactions are involved in the initial stages of many fundamental biological and pathological processes through lectin-carbohydrate binding. The design of high affinity ligands is therefore necessary to study, inhibit and control the processes governed through carbohydrate recognition by their lectin receptors. Carbohydrate-functionalised gold nanoclusters (glyconanoparticles, GNPs) show promising potential as multivalent tools for studies in fundamental glycobiology research as well as biomedical applications. Here we present the synthesis and characterisation of galactose functionalised GNPs and their effectiveness as binding partners for PA-IL lectin from Pseudomonas aeruginosa. Interactions were evaluated by hemagglutination inhibition (HIA), surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) assays. Results show that the gold nanoparticle platform displays a significant cluster glycoside effect for presenting carbohydrate ligands with almost a 3000-fold increase in binding compared with a monovalent reference probe in free solution. The most effective GNP exhibited a dissociation constant (K(d)) of 50 nM per monosaccharide, the most effective ligand of PA-IL measured to date; another demonstration of the potential of glyco-nanotechnology towards multivalent tools and potent anti-adhesives for the prevention of pathogen invasion. The influence of ligand presentation density on their recognition by protein receptors is also demonstrated.     

Surfactant-assisted regulation of polydivinylbenzene nanofibers morphology

In this study, we described a simple surfactant-assisted approach for synthesizing polydivinylbenzene (PDVB) nanofibers with different morphologies and dimensions. By adding different amounts of specific surfactant (1,2-epoxyalkane, fatty acids, and fatty alcohols) during the polymerization of divinylbenzene (DVB), the shape or size of PDVB nanofibers can be changed, for example the diameter has been reduced to 50–100 nm and helical nanofibers has been obtained. This kind of PDVB nanofibers have widespread potential application in nanomaterials and nanofibers with different requirements.     

Novel CuS nanofibers using organogel as a template: controlled by binding sites

A new cholesterol organogelator 1 was synthesized, which was confirmed as an effective gelator for various organic solvents and could self-assemble into network fibers in some organic solvents. Moreover, gelator 1 could act as templates for the synthesis of various CuS nanofibers with different helical pitches. For example, when H(2)S was used as the sulfur source, straight and bending helical CuS nanofibers with a pitch of 100-200 nm could be fabricated in butyl acetate and benzene-butanol gel systems, respectively, while bending CuS nanofibers with a similar helical pitch (ca. 50 nm) could be obtained when thioacetamide was used as the sulfur source in both gel systems. It was first found that the morphologies of inorganic nanofibers could be controlled by the binding sites between the inorganic precursor and the organogel.     

Thermal study of boehmite nanofibers with controlled particle size

Boehmite nanofiber materials with controlled particle size were synthesized without any surfactant by careful tuning of the hydrothermal temperatures, and followed by a series of characterizations. It was found that the boehmite nanofibers became shorter and coarser with the increase of temperature, and resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by in situ HT X-ray diffraction and thermogravimetry–differential scanning calorimetry. All materials showed the phase transition from γ-Al₂O₃ to other forms. Yet the transition temperature was increased with the increase of hydrothermal temperature. The boehmite nanofibers with the largest diameter showed the best thermal stability.     

Chemoenzymatic Synthesis of a Multivalent Aminoglycoside

A polymeric aminoglycoside was prepared by a facile chemoenzymatic reaction. Boc‐protected aminoglycoside, amikacin, was chemoselectively esterified with divinyl sebacate at a hydroxyl group in the C6″ position by protease from Bacillus subtilis. The resulting 3,6′,3″,4?‐tetra‐N‐Boc‐6″‐O‐vinyl sebacate was copolymerized with maltitol 6‐vinyl sebacate to yield a polymeric amikacin. The polymeric amikacin showed a modest inhibitory effect on in vitro protein synthesis, and a little antibiotic activity in minimum inhibitory concentration (MIC) assay in the presence of protease.

The synthesis of Boc‐protected amikacin ester by an enzyme‐catalyzed (protease) esterification.     

Multivalent ions and biomolecules: Attempting a comprehensive perspective

Ions are ubiquitous in nature. They play a key role for many biological processes on the molecular scale, from molecular interactions, to mechanical properties, to folding, to self-organisation and assembly, to reaction equilibria, to signalling, to energy and material transport, to recognition etc. Going beyond monovalent ions to multivalent ions, the effects of the ions are frequently not only stronger (due to the obviously higher charge), but qualitatively different. A typical example is the process of binding of multivalent ions, such as Ca²⁺, to a macromolecule and the consequences of this ion binding such as compaction, collapse, potential charge inversion and precipitation of the macromolecule. Here we review these effects and phenomena induced by multivalent ions for biological (macro)molecules, from the “atomistic/molecular” local picture of (potentially specific) interactions to the more global picture of phase behaviour including, e. g., crystallisation, phase separation, oligomerisation etc. Rather than attempting an encyclopedic list of systems, we rather aim for an embracing discussion using typical case studies. We try to cover predominantly three main classes: proteins, nucleic acids, and amphiphilic molecules including interface effects. We do not cover in detail, but make some comparisons to, ion channels, colloidal systems, and synthetic polymers. While there are obvious differences in the behaviour of, and the relevance of multivalent ions for, the three main classes of systems, we also point out analogies. Our attempt of a comprehensive discussion is guided by the idea that there are not only important differences and specific phenomena with regard to the effects of multivalent ions on the main systems, but also important similarities. We hope to bridge physico-chemical mechanisms, concepts of soft matter, and biological observations and connect the different communities further.     

Physical properties of TEMPO-oxidized bacterial cellulose nanofibers on the skin surface

Water-dispersed bacterial cellulose nanofibers were prepared via an oxidation reaction using 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (TEMPO) as a catalyst. It was found that TEMPO-oxidized bacterial cellulose nanofibers (TOCNs) synthesized via sodium bromide-free methods are similar to those synthesized using sodium bromide. The TOCNs retained their unique structure in water as well as in emulsion. TOCNs adhere to the skin surface while maintaining nanofibrous structures, providing inherent functions of bacterial cellulose, such as high tensile strength, high water-holding capacity, and blockage of harmful substances. When gelatin gels as model skin were coated with TOCNs, the hardness representing the elasticity was increased by 20% compared to untreated gelatin gel because TOCNs could tightly hold the gelatin structure. When porcine skin was treated with TOCNs, carboxymethyl cellulose, and hydroxyethyl cellulose, the initial water contact angles were 26.5°, 76.5°, and 64.1°, respectively. The contact angle of TOCNs dramatically decreased over time as water penetrated the fibrous structure of the TOCN film. When observed by scanning electron microscopy and confocal microscopy, TOCNs on the skin surface provided physical gaps between particles and the skin, blocking the adsorption of particulate matter to the skin surface. On the contrary, the structure of water-soluble polymers was disrupted by an external environment, such as water, so that particulate matter directly attached to the skin surface. Characterization of TOCNs on the skin surface offered insight into the function of nanofibers on the skin, which is important for their applications with respect to the skin and biomedical research.     

Interaction of bacterial endotoxine (lipopolysaccharide) with latex particles: application to latex agglutination immunoassays

The latex agglutination immunoassay technique uses polymer colloids as carriers for antibodies or antigens to enhance the immunological reaction. In this work, the interaction of a lipopolysaccharide (LPS) of Brucella Melitensis with two conventional latexes has been studied. Some experiments on the physical adsorption of the LPS onto these polystyrene beads have been performed and several complexes with different coverage degrees were obtained by modifying the incubation conditions. Regarding the application in the development of diagnostic test systems, it is advisable to study the latex-LPS complexes from an electrokinetic and colloidal stability point of view. The complexes were electrokinetically characterized by measuring the electrophoretic mobility under different redispersion conditions. The colloidal stability was determined by simple turbidity measurements. Experimental and theoretical data have been employed to study the molecular disposition of the LPS in the latex particle surface to compare with the outer membrane of bacterial cells. Latex complexes covered by different LPS amounts showed high colloidal stability and adequate immunoreactivity that remains for a long time period.     

Ion-selective controlled assembly of dendrimer-based functional nanofibers and their ionic-competitive disassembly

The construction of hierarchical materials through controlled self-assembly of molecular building blocks (e.g., dendrimers) represents a unique opportunity to generate functional nanodevices in a convenient way. Transition-metal compounds are known to be able to interact with cationic dendrimers to generate diverse supramolecular structures, such as nanofibers, with interesting collective properties. In this work, molecular dynamics simulation (MD) demonstrates that acetate ions from dissociated Cd(CH(3)COO)(2) selectively generate cationic PPI-dendrimer functional fibers through hydrophobic modification of the dendrimer's surface. The hydrophobic aggregation of dendrimers is triggered by the asymmetric nature of the acetate anions (AcO(-)) rather than by the precise transition metal (Cd). The assembling directionality is also controlled by the concentration of AcO(-) ions in solution. Atomic force (AFM) and transmission electron microscopy (TEM) prove these results. This well-defined directional assembly of cationic dendrimers is absent for different cadmium derivatives (i.e., CdCl(2), CdSO(4)) with symmetric anions. Moreover, since the formation of these nanofibers is controlled exclusively by selected anions, fiber disassembly can be consequently triggered via simple ionic competition by NaCl salt. Ions are here reported as a simple and cost-effective tool to drive and control actively the assembly and the disassembly of such functional nanomaterials based on dendrimers.     

Formation of polyaniline nanofibers: a morphological study

Polyaniline (PANI) powders were prepared by solution precipitation, rapid mixing polymerization, and interfacial polymerization to find the key factors that influence the formation and growth of PANI nanofibers. In chemical oxidative polymerization of aniline, the morphology of the product is mainly determined by aniline concentration. In the case of lower aniline concentration, PANI nanofibers were formed and can be preserved and collected as final product, while in the case of higher aniline concentration, larger sized PANI particles or agglomerates were obtained owing to the growth of the nanofibers. Without participation of the oxidizing step, solid PANI samples with compact structures and dissimilar morphologies were achieved by random accumulation of PANI molecules.     

Application of silicate electrospun nanofibers for cell culture

Silicate produced via the sol–gel process is a biocompatible material that has high purity and high homogeneity. In this study, we evaluated the feasibility of electrospun fibers of silicate formed into silicate nonwoven fabrics (SNF) developed via the sol–gel process as substrates for substance production using Chinese hamster ovarian cells CHO-K1, and as substrates for producing drug metabolism simulators from the human cell line HepG2. We compared the adherent and proliferation profiles of the two cell types on SNF with those profiles produced on a hydroxyapatite-pulp composite fiber sheet (HAPS). During 14 days of cultivation, a greater number of CHO-K1 and HepG2 cells continued to grow on SNF compared to those on HAPS. Per unit volume, the HepG2 cells on SNF showed higher hepatic-specific functions than those on HAPS. These results demonstrate the feasibility of SNF as a cell culture substrate for substrate production, and for producing drug metabolism simulators.     

Synthesis of a fragment of bacterial cell wall

Cell wall is indispensable for survival of bacteria. This large molecular "mesh" encases the entire cytoplasm of bacteria, and it is comprised of repeating backbone units of N-acetyl-glucosamine (NAG)-N-acetyl-muramic acid (NAM). A pentapeptide is attached to each of the lactyl units of the N-acetyl-muramic acid. The cell wall has both cross-linked and non-cross-linked components. In the present paper, we have devised a synthetic route for the preparation of a fragment of the cell wall comprised of a tetrasaccharide (NAG-NAM-NAG-NAM), along with the two appended peptides. We also report the syntheses of three glycosyl donors (compounds 5, 7, and 9) and three glycosyl acceptors (compounds 4, 6, and 8) based on the d-glucosamine structure as a building unit. The synthetic strategy that is disclosed is generally useful in construction of other natural products containing the d-glucosamine as a building block.     

Dextramabs: A Novel Format of Antibody-Drug Conjugates Featuring a Multivalent Polysaccharide Scaffold

Antibody-drug conjugates (ADCs) are multicomponent biomolecules that have emerged as a powerful tool for targeted tumor therapy. Combining specific binding of an immunoglobulin with toxic properties of a payload, they however often suffer from poor hydrophilicity when loaded with a high amount of toxins. To address these issues simultaneously, we developed dextramabs, a novel class of hybrid antibody-drug conjugates. In these architectures, the therapeutic antibody trastuzumab is equipped with a multivalent dextran polysaccharide that enables efficient loading with a potent toxin in a controllable fashion. Our modular chemoenzymatic approach provides an access to synthetic dextramabs bearing monomethyl auristatin as releasable cytotoxic cargo. They possess high drug-to-antibody ratios, remarkable hydrophilicity, and high toxicity in vitro.     

Nonionic surfactant sorption onto the bacterial cell surface: a multi-interaction isotherm

The adsorption of linear polyoxyethylene (POE) alcohol surfactants of the form CxEy onto the surface of a Sphingomonas sp. has been examined. For this study, the alkyl chain length (x) was fixed at 12 and the POE chain length (y) was varied, with y = 4, 7, 9, 10, and 23 ethylene oxide units. Langmuirian isotherms were observed for C12E4 and C12E23, and more complex isotherms were observed for the three intermediate POE chain length surfactants, with C12E7 and C12E9 exhibiting strong S-shaped isotherms. All isotherms showed plateaus near the critical micelle concentration (CMC) with the plateau decreasing with increasing POE chain length. A simple multi-interaction isotherm is proposed that models the sorption isotherm as the sum of two interactions. The first interaction describes monolayer adsorption, whereas the second interaction describes lateral interactions between sorbed surfactant molecules and the formation of surface aggregates. Varying ratios of these two interactions as a function of POE chain length gives rise to the variety of observed isotherm shapes. Results of the isotherm analysis suggest that lateral interactions dominate for surfactants with low POE chain lengths, and the lateral interactions decrease as the POE chain length is increased.     

High Photocatalytic Properties of Zinc OxideNanoparticles with Amidoximated BacterialCellulose Nanofibers as Templates简

The freshly prepared water-wet amidoximated bacterial cellulose （Am-BC） serves as an effective nanoreactor to synthesis zinc oxide nanoparticles by in situ polyol method. The obtained ZnO/Am-BC nanocomposites have been characterized by field emission scanning electron microscopy （FE-SEM）, X-ray diffraction （XRD）, Fourier transformed infrared spectroscopy （FTIR） and thermogravimetric analysis （TGA）. The influence of the zinc acetate concentration on the morphologies and size ofZnO nanoparticles and the possible formation mechanism were discussed. The results indicated that uniform ZnO nanoparticles were homogeneously anchored on the Am-BC nanofibers through strong interaction between the hydroxyl and amino groups of Am-BC and ZnO nanoparticles. The loading content of ZnO nanoparticles is higher using Am-BC as a template than using the unmodified bacterial cellulose. The resultant nanocomposite synthesized at 0.05 wt% shows a high photocatalytic activity （92%） in the degradation of methyl orange.