A network model to correlate conformational change and the impedance spectrum of singleproteins

Abstract

Integrated nanodevices based on proteins or biomolecules are attracting increasing interestin today’s research. In fact, it has been shown that proteins such as azurin andbacteriorhodopsin manifest some electrical properties that are promising for thedevelopment of active components of molecular electronic devices. Here we focus on tworelevant kinds of protein: bovine rhodopsin, prototype of G-protein-coupled-receptor(GPCR) proteins, and the enzyme acetylcholinesterase (AChE), whose inhibition is one ofthe most qualified treatments of Alzheimer’s disease. Both these proteins exert theirfunction starting with a conformational change of their native structure. Our guess is thatsuch a change should be accompanied with a detectable variation of their electricalproperties. To investigate this conjecture, we present an impedance network model ofproteins, able to estimate the different impedance spectra associated with the differentconfigurations. The distinct types of conformational change of rhodopsin and AChE agreewith their dissimilar electrical responses. In particular, for rhodopsin the model predictsvariations of the impedance spectra up to about 30%, while for AChE the same variationsare limited to about 10%, which supports the existence of a dynamical equilibrium betweenits native and complexed states.