Effective biological application of nanocrystalline semiconductor quantum dots continues to be hampered by the lack of easily implemented and widely applicable labeling chemistries. Here, we introduce two new orthogonal nanocrystal bioconjugation chemistries that overcome many of the labeling issues associated with currently utilized approaches. These chemistries specifically target either (1) the ubiquitous amines found on proteins or (2) thiols present in either antibody hinge regions or recombinantly introduced into other proteins to facilitate site-specific labeling. The amine chemistry incorporates aniline-catalyzed hydrazone bond formation, while the sulfhydryl chemistry utilizes nanocrystals displaying surface activated maleimide groups. Both reactive chemistries are rapidly implemented, yielding purified nanocrystal-protein bioconjugates in as little as 3 h. Following initial characterization of the nanocrystal materials, the wide applicability and strong multiplexing potential of these chemistries are demonstrated in an array of applications including immunoassays, immunolabeling in both cellular and tissue samples, in vivo cellular uptake, and flow cytometry. Side-by-side comparison of the immunolabeled cells suggested a functional equivalence between results generated with the amine and thiol-labeled antibody-nanocrystal bioconjugates in that format. Three-color labeling was achieved in the cellular uptake format, with no significant toxicity observed while simultaneous five-color labeling of different epitopes was demonstrated for the immunolabeled tissue sample. Novel labeling applications are also facilitated by these chemistries, as highlighted by the ability to directly label cellular membranes in adherent cell cultures with the thiol-reactive chemistry.

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ABSTRACT:This paper describes the synthesis of active ester copolymers from Nisopropylacrylamide (NIP) with N-acryloxysuccinimide (NAS), aminolysis of active esters, and determination of their average molecular weights. As a model, thermolysin was attached to the polymer to form soluble-insoluble immobilized enzymes capable of being centrifuged above their T" because poly(N-isopropylacylamide) (poly(NIP)) has a lower critical solution temperature (Tc) of about 31-33°C. The effects of immobilization of enzymes have been studied including the amount of active ester, time, pH, temperature, and ratio of polymer to enzyme. The tests of thermal stability and repeated precipitation and separation showed that the use of T, as the technique of separation is possible.KEY WORDS Polymerization / Phase Separating Reactiv\! Polymers / Poly(N-isopropylacrylamide) / Immobilization of Enzyme / Thermolysin /

Modification of polypropylene by hyperbranched grafting with a poly(acrylic acid) graft was carried out using techniques previously used with gold, aluminum, silicon, and polyethylene surfaces. An initial etching oxidation produced a modified polypropylene that was presumed to contain carboxylic acid functional groups (though none were detected by IR spectroscopy). Then, a series of repetitive grafting experiments using an α,ω-diamine derivative of poly(tert-butyl acrylate) were used to produce surfaces containing significant amounts of poly(acrylic acid). The resulting surfaces were characterized by ATR-IR spectroscopy, contact angle measurements, and XPS spectroscopy. Treatment of the surfaces with alkali produced a more hydrophilic carboxylate surface. Treatment of these surfaces first with ethyl chloroformate followed by pentadecylfluorooctylamine produced a hydrophobic fluorinated surface. Mechanical tests show that such surface modification not only serves as a route to modify polypropylene's hydrophilicity/hydrophobicitysuch modification substantially affects the adhesive strength between this modified polypropylene and an epoxy adhesive. Double cantilever beam tests show that adhesion increases from 2 J/m2 for unmodified polypropylene to up to 29 J/m2 with the modified polypropylene.

Ground tire rubber (GTR) with crosslinked structure has hardly any plasticity and processability, which makes its property very poor. Thermal-mechanical shearing devulcanization method can effectively destroy the crosslinked structure and restore GTR a certain extent of plasticity and processability. This article investigated the characteristic and reprocessing performance of reclaimed rubber prepared through thermal-mechanical shearing devulcanization. The relationship between the devulcanization level (indicated by gel fraction and crosslink density) and the mechanical property was analyzed by sufficient experiments. Fourier transform infrared spectroscopy and elemental analyzer studies revealed the chemical structure of GTR changed and many complex reactions occurred after devulcanization. The gel permeation chromatography indicated the specific changes of molecular weight and molecular weight distribution in devulcanization process. The differential scanning calorimetry revealed various vulcanized abilities and vulcanized structures of reclaimed rubber. The scanning electron microscope further confirmed the recovery of plasticity after devulcanization and the distinct vulcanized structures between revulcanizates. The determination of devulcanization level and mechanical properties verified that mechanical properties especially tensile strength reached to the optimum value only at an appropriate devulcanization level.