Photo-reversible Pb2+-complexation in a purely aqueous environment exhibiting a thermosensitive phase transition at a lower critical solution temperature was achieved using a synthetic copolymer composed of N-isopropyl acrylamide and spiropyran acrylate.
Here, we describe the coordinated use of two antibodies with different affinities in a single immunoassay to extend the dynamic range and to enable detection of multiple analytes. The combination of dual antibodies was permitted with a flow-based assay at the antibody concentration below the dissociation constant, enabling affinity to govern the antibody-antigen binding. Both high and low affinity antibodies to estriol were used in combination to extend the range. The binding of each antibody was mutually independent and individually occurred over concentration ranges of 10 pM(-1) nM and 100 pM(-1) microM. The wide dynamic range of 10 pM(-1) microM was thus achieved as summation of the proportional signals to the total binding. When a combination of antibodies toward different antigens was used, it effectively detected multiple analytes within a mixture. In simultaneous analysis of a mixture of estradiol and estriol, the total signal was the sum of the binding signals from anti-estradiol and anti-estriol antibodies. In a further refinement, the individual antibodies were flowed through the flow cell sequentially, allowing the quantification of each binding signal within the combination. With this sequential format, measurement of the individual hormones in the range of 1.6 pM(-1) nM was shown. Furthermore, the same flow format was successfully applied to assay estriol and estradiol hormones in mixtures of six related compounds.
trans-2-Cycloocten-1-one and trans-2-cyclohepten-1-one, which are supposed to be formed by the ultra-violet irradiation of cis-2-cycloocten-1-one and cis-2-cyclohepten-1-one, give Diels-Alder addition products with cyclopentadiene and isoprene.
A sulfobetaine copolymer (1) carrying a photochromic spiropyran residue was synthesized, which reversibly isomerized between the closed and open forms in pure water and in saline by irradiation with visible light. The thermodynamic stability of the open form of the spiropyran methacrylate (SPMA) units of compound 1 was reduced upon increasing NaCl concentration. In addition, photo-reversible and selective Cu 2+ complexation in saline solution ([NaCl] ¼ 1.0 wt%) was achieved using compound 1 with metal ions (Cu 2+ , Zn 2+ , Ni 2+ , or Co 2+ ). Covalently cross-linked compound 1 showed selective Cu 2+ adsorption in pure water. In contrast, the other metal ions were increasingly adsorbed as NaCl concentration increased, resulting in lower selectivity of Cu 2+ ion adsorption with 1, e.g., the ratios of adsorption of Cu 2+ , Zn 2+ , Ni 2+ , and Co 2+ with 1 in 10 wt% saline were 73, 20, 10, and 3%, respectively, while only Cu 2+ adsorption was observed in a solution of 1.0 wt% NaCl. Because the stability of the open form of the SPMA units and the metal complexation of 1 were influenced by NaCl concentration, the electrostatically cross-linked networks of the zwitterionic sulfobetaine units of 1 may be loosened by NaCl addition, resulting in easy entry of metal ions into the network. The order of metal complexation among the four metals corresponded to the Irving-Williams series. Hydrogen-bonded networks of water molecules also may contribute to the relatively ineffective selective adsorption of Cu 2+ ions by 1 compared to the electrically neutral spiropyran-carrying copolymer of N-isopropylacrylamide, 2.
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