Detection of Cytochrome c with Calixarenes Incorporated into Supported Lipid Membranes Via Charge Transient Measurements

The interaction of cytochrome c (cyt c) with the calix[6]arene carboxylic acid derivative (tOct[6]CH2COOH) (CX) incorporated into supported lipid membranes (sBLM) composed of dimyristoylphosphatidylcholine (DMPC) were investigated in the metal/insulator/metal arrangement with the isothermal charge transient spectroscopy (IQTS) in local mode and with voltammetry and measurements of double layer capacitance. Cyt c was detected on hydrated DMPC layers as a distinct IQTS peak with relaxation constant below 100 ms. Incorporation of CX in DMPC increased the sensitivity to cyt c about 50%. Reliable detection limit of cyt c was 30 nM. In sBLMs the capture of cyt c increased the permittivity of both sBLMs, with and without CX, respectively. Nevertheless, cyt c was detected in voltammogram only for DMPC layer contained CX, as a wave at the potential of +0.25 V. This potential is in good agreement with the redox potential of cyt c. Hysteresis in double layer capacitance observed only for the mixed DMPC+CX layer is interpreted by reduction of the charge, which is involved in the ongoing redox reaction.