Redox active films of salicylic acid-based molecules as pH and ion sensors for monitoring ionophore activity in supported lipid deposits

International audience*corresponding authors: [email protected] and [email protected] Abstract: 5-aminosalicylic acid and salicylic acid have been used to form redox active films onto glassy carbon electrodes through recurrent cyclic voltammetry. The variation of the formal potential of the film obtained from 5-aminosalicylic acid as a function of pH is linear over the entire pH range studied (pH 2 to 10) with a slope of-80 mV per pH unit. Salicylic acid-based redox active films permit the detection of sodium and potassium ions (with a slope of-10 mV per 1 mM of cation) and chloride (with a slope of +11 mV per 1 mM of chloride). A lipid deposit of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) onto these modified electrodes allowed the integration of ionophores (valinomycin and nigericin) and the monitoring of the pH and potassium ion concentration variation at the modified electrode / lipid deposit interface

Assisted lipid deposition by reductive electrochemical aryldiazonium grafting and insertion of the antiport NhaA protein in this stable biomimetic membrane

International audienceQuartz crystal microbalance studies have been carried out to monitor the fusion of lipid vesicles (pure 1,2-dimyristoyl-sn-glycero-3-phosphocholine, DMPC) and mixed vesicles (DMPC and 4-decylaniline). In order to increase the stability of the lipid deposits onto the electrodes, we have developed an original approach involving electrografting of adsorbed mixed vesicles. Aryldiazonium salts generated in situ from 4-decylaniline (4DA) present in adsorbed and fused mixed vesicles at the electrode surface allow their cathodic reduction and subsequent grafting. The stability of the supported lipid deposit has been shown to significantly increase from less than one day for pure DMPC to about two weeks with the lipid deposition assisted by electrochemical grafting. In this stable lipid deposit, the insertion of the sodium/proton antiporter membrane protein (NhaA) or its inactive mutant has been carried out by fusion of proteoliposomes. This has been followed by characterization of the inserted protein activity by cyclic voltammetry onto an electrode previously modified by an adsorbed pH sensor (2-anthraquinone sulfonate). Activation of the protein function by sodium ions leads to a shift of the interfacial pH and confirms the integrity of the immobilized NhaA

Dynamics of the Lithium Amide/Alkyllithium Interactions: Mixed Dimers and Beyond

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