Gold Nanoparticle Assisted Assembly of a Heme Protein for Enhancement of Long-Range Interfacial Electron Transfer

Abstract

Interfacial electron transfer (ET) of biological macromolecules such as metalloproteins is the key process in bioelectrochemistry, enzymatic electrocatalysis, artificial ET chains, single-molecule electronic amplification and rectification, and other phenomena associated with the area of bioelectronics. A key challenge in molecular bioelectronics is to improve the efficiency of long-range charge transfer. The present work shows that this can be achieved by nanoparticle (NP) assisted assembly of cytochrome c (cyt c) on macroscopic single-crystalline electrode surfaces. We present the synthesis and characterization of water-soluble gold nanoparticles (AuNPs) with core diameter 3−4 nm and their application for the enhancement of long-range interfacial ET of a heme protein. Gold nanoparticles were electrostatically conjugated with cyt c to form nanoparticle−protein hybrid ET systems with well-defined stoichiometry. The systems were investigated in homogeneous solution and at liquid/solid interface. Conjugation of cyt c results in a small but consistent broadening of the nanoparticle plasmon band. This phenomenon can be explained in terms of long-range electronic interactions between the gold nanoparticle and the protein molecule. When the nanoparticle−protein conjugates are assembled on Au(111) surfaces, long-range interfacial ET across a physical distance of over 50 Å via the nanoparticle becomes feasible. Moreover, significant enhancement of the interfacial ET rate by more than an order of magnitude compared with that of cyt c in the absence of AuNPs is observed. AuNPs appear to serve as excellent ET relays, most likely by facilitating the electronic coupling between the protein redox center and the electrode surface.

Direct measurement and modulation of single-molecule coordinative bonding forces in a transition metal complex

“…Reversible interfacial ET was observed, and the ET rate was estimated as 25 s À 1 by the Laviron method (Supplementary Fig. S3) 32,33 . The surface population of terpy, estimated from the reductive desorption ( Supplementary Fig.…”

Optical investigation of the electron transfer protein azurin–gold nanoparticle system

“…Moreover, when biomolecules are conjugated with nanoparticles, the mixing of their energy levels has been shown to favour the occurrence of either energy transfer or electron transfer phenomena [7,8]. In this way, it is possible to study fundamental processes characterizing the interaction of metal nanoparticles with organic or biological molecules [4,9,10]. Furthermore, nanoparticle properties can be exploited for realizing nanohybrid systems for various applications, also thanks to the possibility to suitably design their characteristics with a proper selection of the employed biotic element [3,[11][12][13].…”

“…It has been reported that the analysis of the overall characteristics of the plasmon band can be exploited to elucidate phenomena occurring at nanoparticle interface, including bioconjugation and molecular recognition [10,36]. Accordingly, three factors can be invoked as possible causes of the plasmon band shift and/or broadening detected in the absorption spectra of Az+AuNP solutions: (a) aggregation of nanoparticles upon bioconjugation, (b) electronic communication between the Az redox center and the gold nanoparticle, and (c) changes in local dielectric environments.…”

A facile method to prepare noble metal nanoparticles modified Self-Assembly (SAM) electrode

“…Kolb et al modified the Au (111) electrode with Zn, Fe and Cu nanoclusters by electron probe [15,16], however, the method is far from universal since it needs strict control and complicated operation, the area of electrode being modified is greatly limited so the efficiency is low. In recent years, assembling the surface functional NPs onto electrode was commonly used to form modified electrode [17,18]. Generally, in this method, ligands with strong affinity to Au (such as thiol) was adopted to react with weak ligands (such as citrate [19] and phenylphenol [20]) protected Au NPs, forming functional Au NPs, and then the functional NPs were adsorbed onto the electrode surface to form NPs modified electrode.…”