Topological and Electron‐Transfer Properties of Yeast Cytochrome c Adsorbed on Bare Gold Electrodes

Abstract

The redox metalloprotein yeast cytochrome c was directly self-chemisorbed on "bare" gold electrodes through the free sulfur-containing group Cys102. Topological, spectroscopic, and electron transfer properties of the immobilised molecules were investigated by in situ scanning probe microscopy and cyclic voltammetry. Atomic force and scanning tunnelling microscopy revealed individual protein molecules adsorbed on the gold substrate, with no evidence of aggregates. The adsorbed proteins appear to be firmly bound to gold and display dimensions in good agreement with crystallographic data. Cyclic voltammetric analysis showed that up to 84% of the electrode surface is functionalised with electroactive proteins whose measured redox midpoint potential is in good agreement with the formal potential. Our results clearly indicate that this variant of cytochrome c is adsorbed on bare gold electrodes with preservation of morphological properties and redox functionality.

Topological and dynamical properties of Azurin anchored to a gold substrate as investigated by molecular dynamics simulation

“…Notably, higher standard deviations for both θ and Φ values were detected for Plastocyanin anchored to gold by a single sulphur of the disulphide group [11,13]. A similar result has been also obtained for yeast cytochrome c bound to gold through the thiol from its native cystein [6]. These results find a correspondence with the fact that the macromolecule maintain a higher degree of freedom when it is bound to gold by a single atom.…”

“…In this respect, a direct binding of molecules to electrodes limits the active site-metal distance and could favour an efficient ET rate. To such a purpose, the chemi-adsorption of proteins on gold electrodes can be achieved by exploiting the high affinity of either intrinsic or engineered disulphides and/or thiol groups for gold [5,6]. A wealth of experimental techniques has been applied to investigate the morphological and conductive properties of redox proteins self-assembled on metal electrodes [7][8][9].…”

Electron tunneling properties of outer-membrane decaheme cytochromes from Shewanella oneidensis

“…Pass energy, 17.9 eV. and the molecular weights of OmcA and MtrC, we expect that individual protein molecules should appear as 'bumps' on the order of a few nanometers in diameter (e.g., Friis et al, 1999;Chi et al, 2000Chi et al, , 2001Davis and Hill, 2002;Andolfi et al, 2003;Bonanni et al, 2003;Hansen et al, 2003;Andolfi et al, 2004b;Zhang et al, 2004). No such features were initially observed.…”

“…Therefore, despite the numerous recent examples in the literature that have utilized STM on metalloproteins in air as an effective means of single-molecule analysis (e.g., Davis et al, 2000;Chi et al, 2001;Andolfi et al, 2003;Bonanni et al, 2003;Alliata et al, 2004;Andolfi et al, 2004a,b;Davis et al, 2004), there is always a concern regarding effects of the STM measurement itself on the proteins under study. However, it is clear from the high reproducibility of the STM images and TS data in this study that the electric fields associated with STM operation are not irreversibly altering the proteins.…”

Preserved enzymatic activity of glucose oxidase immobilized on unmodified electrodes for glucose detection

“…A device with superior performance is c haracterized by fa st enzyme-e lectrode electron transfer (com munication) with the enzyme bei ng able to perform molec ular recognition. The most obvious approach to achievi ng enhanced electron transfer is to immobilize enzymes directly onto the bare/un modified electrode surface (Bonanni et al .. 2003: Heering et al" 2004: Wang et aI., 2006Wang and Yau, 2005). However, inorganic electrodes and enzymes are incompatible materilli s that, in geneml , enzymes unde rgo denaturation upon immobi lization on bare e lectrodes (Wen et HI., 1997) and, there fore, lose their enzymatic activ ities.…”