A Network Model to Correlate Conformational Change and Impedance Spectrum of Single Proteins

Integrated nanodevices based on proteins or biomolecules are attracting an increasing interest in today research. In fact, it has been shown that proteins, like azurin and bacteriorhodopsin, manifest some electrical properties promising for the development of active components of molecular electronic devices. Here we focus on two relevant kinds of proteins: The bovine rhodopsin, prototype of GPCR proteins, and the enzyme acetylcholinesterase (AChE), whose inhibition is one of the most qualified treatments of Alzheimer disease. Both these proteins exert their function starting with a conformational change of their native structure. Our guess is that such a change should be accompanied with a detectable variation of their electrical properties. To investigate this conjecture, we present an impedance network model of proteins, able to estimate the different impedance spectra associated with the different configurations. The distinct types of conformational change of rhodopsin and AChE agree with their dissimilar electrical responses. In particular, for rhodopsin the model predicts variations of the impedance spectra up to about 30 \% while for AChE the same variations are limited to about a 10 \%, which supports the existence of a dynamical equilibrium between its native and complexed states.