Voltammetry metalloprotein

It has been shown that a variety of complex redox-linked properties of metalloproteins can be probed by voltammetry of these species adsorbed on the electrodes. Armstrong has been a key investigator in this area, and he has elegantly reviewed salient recent advances (33) the following paragraphs merely summarize some of the highlights of his review... 

Electron Transport and Two-Dimensional Organization of Metalloprotein Adsorbates Investigated by Cyclic Voltammetry and In Situ Scanning Tunnelling and Atomic Force Microscopy... 

The rate constants also hold a useful clue to concentration and time ranges for new investigations of intermolecular ET processes of cyt c4 in solution, from which the intramolecular rate constants may be substantiated. Voltammetry, therefore, stands forward as a powerful tool towards otherwise elusive ET dynamics in composite metalloproteins. 

Our short overview illustrates some prospects for investigation of metallop-rotein dynamics at metal-solution interfaces. Cyclic voltammetry of small single metalloproteins is straightaway feasible. Reversible electrochemistry can be achieved but molecular detail such as adsorption patterns and precise promoter function remain elusive. 

Armstrong, F. A., Heering, H. A., and Hirst, J., 1997, Reactions of complex metalloproteins studied by protein-film voltammetry, Chem. Soc. Rev. 26 169nl79. 

Armstrong, F.A. (1990) Probing metalloproteins by voltammetry. Bioinorganic Chemistry, 72, 137-230. 

Electrochemically controlled SAMs of the alkanethiol class characterized to high voltammetric resolution and to molecular and sub-molecular structural in situ STM resolution have been reviewed recently [60, 151]. We note here first some issues of importance to functionalized alkanethiols as linker molecules for gentle immobilization of fully functional redox metalloprotein monolayers on singlecrystal Au(lll) electrode surfaces. We discuss next specifically the functionalized alkanethiols cysteine (Cys) and homocysteine (Hey). These two molecules represent a core protein building block and a core metabolite, respectively. The former has been used to display unique sub-molecular in situ STM resolution [152]. The latter shows a unique dual surface dynamics pattern that could be followed both by single-molecule in situ STM and by high-resolution capacitive voltammetry. 

Davis, J.J., Hill, H.A.O., and Bond, A.M. (2000) The application of electrochemical scanning probe microscopy to the interpretation of metalloprotein voltammetry. 

One line in bioelectrochemistry is rooted in electrochemical techniques, spectroscopy, and other physical chemical techniques. Linear and cyclic voltammetry are central.Other electrochemical techniques include impedance and electroreflectance spectroscopy," ultramicro-electrodes, and chronoamperometry. To this come spectroscopic techniques such as infiared, surface enhanced Raman and resonance Raman,second harmonic generation, surface Plasmon, and X-ray photoelectron spectroscopy. A second line has been to combine state-of-the-art physical electrochemistry with corresponding state-of-the-art microbiology and chemical S5mthesis. The former relates to the use of a wide range of designed mutant proteins, " the latter to chemical synthesis or de novo designed synthetic redox metalloproteins. " " ... 

With a few exceptions, redox metalloprotein voltammetry on gold surfaces is unstable or absent unless either the electrode is modified by chemisorbed monolayers of linker or promoter molecules, or the protein is modified by insertion of non-native amino acid residues. The linker molecules are usually thiol-containing molecules which adsorb strongly on the Au-surface. 

Figure 8-11. Overview of metalloproteins recently characterized by single-crystal-crystal protein film voltammetry and by in situ STM to single-molecnle resolntion. Top left P.

Overall the single-crystal voltammetry, surface promoter sensitivity, and in situ STM of PJ d illuminate procedures and approaches to highly increased resolution in the bioelectrochemical mapping of redox metalloproteins, approaching the electrochemical resolution of small molecular adsorbate molecules. 

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