Spectroscopic and electrochemical studies of horse myoglobin in dimethyl sulfoxide.
Abstract: This paper reports the first report of rapid, reversible direct electron transfer between a redox protein, specifically, horse myoglobin, and a solid electrode substrate in nonaqueous media and the spectroscopic (UV-vis, fluorescence, and resonance Raman) characterization of the relevant redox forms of myoglobin (Mb) in dimethyl sulfoxide (DMSO). In DMSO, the heme active site of metmyoglobin (metMb) appears to remain six-coordinate high-spin, binding water weakly. Changes in the UV-fluorescence spectra for metMb in DMSO indicate that the protein secondary structure has been perturbed and suggest that helix A has moved away from the heme. UV-vis and RR spectra for deoxyMb in DMSO suggest that the heme iron is six-coordinate low-spin, most likely coordinating DMSO. Addition of CO to deoxyMb in DMSO produces a single, photostable six-coordinate CO adduct. UV-vis and RR for Mb-CO in DMSO are consistent with a six-coordinate low-spin heme iron binding His93 weakly, if at all. The polarity of the distal heme pocket is comparable to that of the closed form of horse Mb-CO in aqueous solution, pH 7. Direct electron transfer between horse Mb and Au in DMSO solution was investigated by cyclic voltammetry. Mb exhibits stable and well-defined electrochemical responses that do not appear to be affected by the water content (1.3-7.5%). The electrochemical characteristics are consistent with a one-electron, quasi-reversible, diffusion-controlled charge transfer process at Au. E degrees for horse Mb in DMSO at Au is -0.241+/-0.005 V vs. NHE. The formal heterogeneous electron transfer rate constant, calculated from delta E(p) at 20 mV/s, is 1.7+/-0.5 x 10(-4) cm/s. The rate, which is unaffected by the presence of 1.3-7.5% water, is competitive with that previously reported for horse Mb in aqueous solution.
Publication Date: 2002-08-30 PubMed ID: 12459902DOI: 10.1007/s00775-002-0392-9Google Scholar: Lookup
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- Journal Article
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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The research article focuses on studying the electron transfer potential and characteristics of horse myoglobin, a type of protein, in a medium of dimethyl sulfoxide. The paper explores the changes in the structure of the protein as well as the polarity of the pocket where the protein binds using spectroscopic and electrochemical techniques.
Understanding the Redox Reactions
- The paper carries out the first exploration of rapid and reversible direct electron transfer, which is a type of redox reaction, between a redox protein (horse myoglobin) and a stable electrode substrate in a nonaqueous medium.
- This manifests how horse myoglobin in a dimethyl sulfoxide (DMSO) environment interacts with electrons, which is crucial in understanding its functioning.
Spectroscopic Characterization
- These redox reactions are characterized spectroscopically using UV-visible light, fluorescence, and resonance Raman techniques.
- Different states of myoglobin namely the deoxyMb and Mb-CO are assessed in a DMSO environment using these spectroscopic techniques, shedding light on the structural changes associated with the protein particularly its heme active site, when water is weakly bound to it (metMb).
- The fluorescence indicates disturbances in the protein’s secondary structure and suggests the A helix is moving away from the heme — the molecule in blood that carries oxygen.
Electrochemical Studies
- The experiment also involved investigating direct electron transfers between horse myoglobin and gold in a DMSO solution by means of cyclic voltammetry — a type of electrochemical measurement.
- The myoglobin showcased stable and defined electrochemical responses that appeared to be unaffected by the water content varying from 1.3% to 7.5%.
- The electrochemical characteristics pointed towards a diffusion-controlled, one-electron, quasi-reversible charge transfer process happening at the gold electrode.
Key Findings
- The researchers found that the formal heterogeneous electron transfer rate constant estimation was 1.7±0.5 x 10^-4 cm/s. This rate is comparable to the rate previously reported for horse myoglobin in an aqueous solution.
- The results, therefore, provide a significant understanding of the behaviour of horse myoglobin in nonaqueous media, specifically DMSO, opening avenues for potential future research and applications.
Cite This Article
APA
Li QC, Mabrouk PA.
(2002).
Spectroscopic and electrochemical studies of horse myoglobin in dimethyl sulfoxide.
J Biol Inorg Chem, 8(1-2), 83-94.
https://doi.org/10.1007/s00775-002-0392-9 Publication
Researcher Affiliations
- Department of Chemistry, Northeastern University, Boston, MA 02115, USA.
MeSH Terms
- Animals
- Binding Sites
- Dimethyl Sulfoxide / chemistry
- Electrochemistry / methods
- Electron Transport
- Gold / chemistry
- Heme / chemistry
- Horses
- Metmyoglobin / chemistry
- Myoglobin / chemistry
- Protein Structure, Secondary
- Spectrum Analysis / methods
- Water / chemistry
Citations
This article has been cited 4 times.- Fang R, Jing H, Chai Z, Zhao G, Stoll S, Ren F, Liu F, Leng X. Design and characterization of protein-quercetin bioactive nanoparticles. J Nanobiotechnology 2011 May 17;9:19.
- Perriman AW, Brogan AP, Cölfen H, Tsoureas N, Owen GR, Mann S. Reversible dioxygen binding in solvent-free liquid myoglobin. Nat Chem 2010 Aug;2(8):622-6.
- Figueiredo KC, Ferraz HC, Borges CP, Alves TL. Structural stability of myoglobin in organic media. Protein J 2009 Jun;28(5):224-32.
- Rezaei-Zarchi S, Saboury AA, Ghourchian H, Hong J, Barzegar A, Norouzi P, Moosavi-Movahedi AA, Ganjali MR, Javed A. Electrochemical investigation of the effect of some organic phosphates on haemoglobin. J Biosci 2007 Mar;32(2):271-8.
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