Herein, we describe a new molecular autocatalytic reaction scheme based on a H2O2-mediated deprotection of a boronate ester probe into a redox cycling compound, generating an exponential signal gain in the presence of O2 and a reducing agent or enzyme. For such a purpose, new chemosensing probes built around a naphthoquinone/naphthohydroquinone redox-active core, masked by a self-immolative boronic ester protecting group, were designed. With these probes, typical autocatalytic kinetic traces with characteristic lags and exponential phases were obtained using either a UV-visible or fluorescence optical detection, or also using an electrochemical monitoring. Detection of concentrations as low as 0.5 µM H2O2 and 0.5 nM of a naphthoquinone derivative were achieved in a relatively short time (< 1 hr). From kinetic analysis of the two cross-activated catalytic loops associated to the autocatalysis, the key parameters governing the autocatalytic reaction network were determined, indirectly showing that the analytical performances are currently limited by the slow nonspecific self-deprotection of boronate probes. Collectively, the present results demonstrate the potential of this new exponential molecular amplification strategy, which, due to its generic nature and modularity, is quite promising for coupling to a wide range of bioassays involving H2O2 or redox cycling compounds, or for being used as a new building block in the development of more complex chemical reaction networks.
C407 is a compound that corrects the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein carrying the p.Phe508del (F508del) mutation. We investigated the corrector effect of c407 and its derivatives on F508del-CFTR protein. Molecular docking and dynamics simulations combined with site-directed mutagenesis suggested that c407 stabilizes the F508del-Nucleotide Binding Domain 1 (NBD1) during the co-translational folding process by occupying the position of the p.Phe1068 side chain located at the fourth intracellular loop (ICL4). After CFTR domains assembly, c407 occupies the position of the missing p.Phe508 side chain. C407 alone or in combination with the F508del-CFTR corrector VX-809, increased CFTR activity in cell lines but not in primary respiratory cells carrying the F508del mutation. A structure-based approach resulted in the synthesis of an extended c407 analog G1, designed to improve the interaction with ICL4. G1 significantly increased CFTR activity and response to VX-809 in primary nasal cells of F508del homozygous patients. Our data demonstrate that in-silico optimized c407 derivative G1 acts by a mechanism different from the reference VX-809 corrector and provide insights into its possible molecular mode of action. These results pave the way for novel strategies aiming to optimize the flawed ICL4–NBD1 interface.
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