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Erol Akyilmaz Gizem Oyman Ezgi Cınar Gorkem Odabas 《Preparative biochemistry & biotechnology》2017,47(1):86-93
A new biosensor based on catalase enzyme immobilized on electrochemically constructed polyaniline (PANI) film modified with glutaraldehyde has been developed for the determination of hydrogen peroxide (H2O2) in milk samples. Assembly processes of polyaniline and immobilization of the enzyme were monitored with the help of electrochemical impedance spectroscopy. Amperometric measurements have been performed at cathodic peak (?0.3?V vs. Ag/AgCI) which was attributed to reduction of PANI. Hydrogen peroxide was determined by using amperometric method at ?0.3?V. The biosensor responses were correlated linearly with the hydrogen peroxide concentrations between 5.0?×?10?6 and 1.0?×?10?4?M by amperometric method. Detection limit of the biosensor is 2.18?×?10?6?M for H2O2. In the optimization studies of the biosensor, some parameters such as optimum pH, temperature, concentration of aniline, amount of enzyme, and number of scans during electropolymerization were investigated. 相似文献
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Shan-Xue Jin Christopher Bartolome Junko A. Arai Laurel Hoffman B. Gizem Uzturk Rajendra Kumar-Singh M. Neal Waxham Larry A. Feig 《The Journal of biological chemistry》2014,289(23):16551-16564
Ras-GRF1 (GRF1) and Ras-GRF2 (GRF2) constitute a family of similar calcium sensors that regulate synaptic plasticity. They are both guanine exchange factors that contain a very similar set of functional domains, including N-terminal pleckstrin homology, coiled-coil, and calmodulin-binding IQ domains and C-terminal Dbl homology Rac-activating domains, Ras-exchange motifs, and CDC25 Ras-activating domains. Nevertheless, they regulate different forms of synaptic plasticity. Although both GRF proteins transduce calcium signals emanating from NMDA-type glutamate receptors in the CA1 region of the hippocampus, GRF1 promotes LTD, whereas GRF2 promotes θ-burst stimulation-induced LTP (TBS-LTP). GRF1 can also mediate high frequency stimulation-induced LTP (HFS-LTP) in mice over 2-months of age, which involves calcium-permeable AMPA-type glutamate receptors. To add to our understanding of how proteins with similar domains can have different functions, WT and various chimeras between GRF1 and GRF2 proteins were tested for their abilities to reconstitute defective LTP and/or LTD in the CA1 hippocampus of Grf1/Grf2 double knock-out mice. These studies revealed a critical role for the GRF2 CDC25 domain in the induction of TBS-LTP by GRF proteins. In contrast, the N-terminal pleckstrin homology and/or coiled-coil domains of GRF1 are key to the induction of HFS-LTP by GRF proteins. Finally, the IQ motif of GRF1 determines whether a GRF protein can induce LTD. Overall, these findings show that for the three forms of synaptic plasticity that are regulated by GRF proteins in the CA1 hippocampus, specificity is encoded in only one or two domains, and a different set of domains for each form of synaptic plasticity. 相似文献
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