Molecularly Regulated Reversible DNA Polymerization.
ABSTRACT: Natural polymers are synthesized and decomposed under physiological conditions. However, it is challenging to develop synthetic polymers whose formation and reversibility can be both controlled under physiological conditions. Here we show that both linear and branched DNA polymers can be synthesized via molecular hybridization in aqueous solutions, on the particle surface, and in the extracellular matrix (ECM) without the involvement of any harsh conditions. More importantly, these polymers can be effectively reversed to dissociate under the control of molecular triggers. Since nucleic acids can be conjugated with various molecules or materials, we anticipate that molecularly regulated reversible DNA polymerization holds potential for broad biological and biomedical applications.
Project description:Hyperbranched polyisoprene was prepared by anionic copolymerization under high vacuum condition. Size exclusion chromatography was used to characterize the molecular weight and branching nature of these polymers. The characterization by differential scanning calorimetry and melt rheology indicated lower Tg and complex viscosity in the branched polymers as compared with the linear polymer. Degradation kinetics of these polymers was explored using thermogravimetric analysis via non-isothermal techniques. The polymers were heated under nitrogen from ambient temperature to 600°C using heating rates from 2 to 15°C min-1. Three kinetics methods namely Friedman, Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose were used to evaluate the dependence of activation energy (Ea ) on conversion (?). The hyperbranched polyisoprene decomposed via multistep mechanism as manifested by the nonlinear relationship between ? and Ea while the linear polymer exhibited a decline in Ea at higher conversions. The average Ea values range from 258 to 330 kJ mol-1 for the linear, and from 260 to 320 kJ mol-1 for the branched polymers. The thermal degradation of the polymers studied involved one-dimensional diffusion mechanism as determined by Coats-Redfern method. This study may help in understanding the effect of branching on the rheological and decomposition kinetics of polyisoprene.
Project description:Although numerous small molecules have been synthesized with sulfenamide bonds (R(2)N-SR), this is the first report of the synthesis of polysulfenamides. These polymers are readily synthesized at room temperature using secondary diamines and dithiosuccinimides. The dithiosuccinimides were readily synthesized in one step by the reaction of dithiols such as HS(CH(2))(6)SH with N-chlorosuccinimide. The resulting dithiosuccinimides were either recrystallized or readily purified by chromatography on silica gel and required no special handling. The conversions of polymerization ranged from 95 to 98%, and the molecular weights of the polymer reached as high as 6,300 g mol(-1). The sulfenamide bond was very stable in organic solvents, and no degradation was observed under atmospheric conditions in C(6)D(6) for 30 days. In contrast, the sulfenamide bond readily decomposed in less than 12 h in D(2)O. Polysulfenamides were fabricated into micron-sized particles loaded with dye and endocytosed into JAWSII immature dendritic and HEK293 cells. Polysulfenamides represent a new class of polymers that are readily synthesized, stable in aprotic solvents, and readily degrade in water.
Project description:A multiprotein complex polarisome nucleates actin cables for polarized cell growth in budding yeast and filamentous fungi. However, the dynamic regulations of polarisome proteins in polymerizing actin under physiological and stress conditions remains unknown. We identify a previously functionally unknown polarisome member, actin-interacting-protein 5 (Aip5), which promotes actin assembly synergistically with formin Bni1. Aip5-C terminus is responsible for its activities by interacting with G-actin and Bni1. Through N-terminal intrinsically disordered region, Aip5 forms high-order oligomers and generate cytoplasmic condensates under the stresses conditions. The molecular dynamics and reversibility of Aip5 condensates are regulated by scaffolding protein Spa2 via liquid-liquid phase separation both in vitro and in vivo. In the absence of Spa2, Aip5 condensates hamper cell growth and actin cable structures under stress treatment. The present study reveals the mechanisms of actin assembly for polarity establishment and the adaptation in stress conditions to protect actin assembly by protein phase separation.
Project description:The core-shell structure molecularly imprinted magnetic nanospheres towards hypericin (Fe₃O₄@MIPs) were prepared by mercapto-alkyne click polymerization. The shape and size of nanospheres were characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). The nanospheres were analyzed by FTIR spectroscopy to verify the thiol-yne click reaction in the presence or absence of hypericin. The Brunauer⁻Emmet⁻Teller (BET) method was used for measuring the average pore size, pore volume and surface area. The Fe₃O₄@MIPs synthesized displayed a good adsorption capacity (Q = 6.80 µmol·g-1). In addition, so-prepared Fe₃O₄@MIPs showed fast mass transfer rates and good reusability. The method established for fabrication of Fe₃O₄@MIPs showed excellent reproducibility and has broad potential for the fabrication of other core-shell molecularly imprinted polymers (MIPs).
Project description:In this report, a series of polycations are designed and synthesized by conjugating reactive oxygen species (ROS)-responsive thioacetal-linkers to low molecular weight (LMW) polyethylenimine (PEI) via ring-opening polymerization. Their structure?activity relationships (SARs) as gene delivery vectors are systematically studied. Although the MWs of the target polymers are only ~9 KDa, they show good DNA binding ability. The formed polyplexes, which are stable toward serum but decomposed under ROS-conditions, have appropriate sizes (180~300 nm) and positive zeta-potentials (+35~50 mV). In vitro experiments reveal that these materials have low cytotoxicity, and higher transfection efficiency (TE) than controls. Furthermore, the title polymers exhibit excellent serum tolerance. With the present of 10% serum, the TE of the polymers even increases up to 10 times higher than 25 KDa PEI and 9 times higher than Lipofectamine 2000. The SAR studies also reveal that electron-withdrawing groups on the aromatic ring in 4a may benefit to balance between the DNA condensation and release for efficient gene transfection.
Project description:Low cross-link density thermally reversible networks were successfully synthesized from jatropha and sunflower oils. The oils were epoxidized and subsequently reacted with furfurylamine to attach furan groups onto the triglycerides, preferably at the epoxide sites rather than at the ester ones. Under the same reaction conditions, the modified jatropha oil retained the triglyceride structure more efficiently than its sunflower-based counterpart, i.e., the ester aminolysis reaction was less relevant for the jatropha oil. These furan-modified oils were then reacted with mixtures of aliphatic and aromatic bismaleimides, viz. 1,12-bismaleimido dodecane and 1,1'-(methylenedi-4,1-phenylene)bismaleimide, resulting in a series of polymers with Tg ranging between 3.6 and 19.8 °C. Changes in the chemical structure and mechanical properties during recurrent thermal cycles suggested that the Diels-Alder and retro-Diels-Alder reactions occurred. However, the reversibility was reduced over the thermal cycles due to several possible causes. There are indications that the maleimide groups were homopolymerized and the Diels-Alder adducts were aromatized, leading to irreversibly cross-linked polymers. Two of the polymers were successfully applied as adhesives without modifications. This result demonstrates one of the potential applications of these polymers.
Project description:Congo red (CR) is an anionic azo dye widely used in many industries including pharmaceutical, textile, food and paint industries. The disposal of huge amount of CR into the various streams of water has posed a great threat to both human and aquatic life. Therefore, it has become an important aspect of industries to remove CR from different water sources. Molecular imprinting technology is a very slective method to remove various target pollutant from environment. In this study a precipitation polymerization was employed for the effective and selective removal of CR from contaminated aqueous media. A series of congo red molecularly imprinted polymers (CR-MIPs) of uniform size and shape was developed by changing the mole ratio of the components. The optimum ratio (0.1:4: 20, template, functional monomer and cross-linking monomer respectively) for CR1-MIP from synthesized polymers was able to rebind about 99.63% of CR at the optimum conditions of adsorption parameters (contact time 210 min, polymer dosage 0.5 g, concentration 20 ppm and pH 7). The synthesized polymers were characterized by various techniques such as Fourier Infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), and Brumauer-Emmett-Teller (BET). The polymer particles have successfully removed CR from different aqueous media with an efficiency of about?~?90%.
Project description:The literature concerning the oxidative oligomerization and polymerization of various arylamines, e.g., aniline, substituted anilines, aminonaphthalene and its derivatives, catalyzed by oxidoreductases, such as laccases and peroxidases, in aqueous, organic, and mixed aqueous organic monophasic or biphasic media, is reviewed. An overview of template-free as well as template-assisted enzymatic syntheses of oligomers and polymers of arylamines is given. Special attention is paid to mechanistic aspects of these biocatalytic processes. Because of the nontoxicity of oxidoreductases and their high catalytic efficiency, as well as high selectivity of enzymatic oligomerizations/polymerizations under mild conditions-using mainly water as a solvent and often resulting in minimal byproduct formation-enzymatic oligomerizations and polymerizations of arylamines are environmentally friendly and significantly contribute to a "green" chemistry of conducting and redox-active oligomers and polymers. Current and potential future applications of enzymatic polymerization processes and enzymatically synthesized oligo/polyarylamines are discussed.
Project description:Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications.
Project description:The use of inorganic nanoparticles (NPs) for biosensing requires that they exhibit high colloidal stability under various physiological conditions. Here, we report on a general approach to render hydrophobic NPs into hydrophilic ones that are ready for bioconjugation. The method uses peglyated polymers conjugated with multiple dopamines, which results in multidentate coordination. As proof-of-concept, we applied the coating to stabilize ferrite and lanthanide NPs synthesized by thermal decomposition. Both polymer-coated NPs showed excellent water solubility and were stable at high salt concentrations under physiological conditions. We used these NPs as molecular-sensing agents to detect exosomes and bacterial nucleic acids.