• Title, Summary, Keyword: redox potentials

Search Result 82, Processing Time 0.036 seconds

$^1H$ NMR Estimation of Multi-Redox potentials of Cytochrome $c_3$ from Desulfovibrio vulgaris Hildenborough

  • 박장수;강신원;최성낙
    • Bulletin of the Korean Chemical Society
    • /
    • v.16 no.4
    • /
    • pp.331-336
    • /
    • 1995
  • The macroscopic and microscopic redox potentials of tetrahemoprotein, cytochrome c3 from Desulfovibrio vulgaris(Hildenborough) (DvH) were estimated from 1H NMR and differential pulse polarography(DPP). Five sets of NMR resonances were confirmed by a redox titration. They represent cytochrome c3 molecules in five macroscopic redox states. The electron transfer in cytochrome c3 involves four consecutive one-electron steps. The saturation transfer method was used to determine the chemical shifts of eight heme methyl resonances in five different oxidation states. Thirty two microscopic redox potentials were estimated. The results showed the presence of a strong positive interaction between a pair of particular hemes. Comparing the results with those of Desulfovibrio vulgaris Miyazaki F (DvMF), it was observed that the two proteins resemble each other in overall redox pattern, but there is small difference in the relative redox potentials of four hemes.

  • PDF

Regulation Mechanism of Redox Reaction in Rubredoxin

  • Tongpil Min;Marly K. Eidsness;Toshiko Ichiye;Kang, Chul-Hee
    • Journal of Microbiology
    • /
    • v.39 no.3
    • /
    • pp.149-153
    • /
    • 2001
  • The electron transfer reaction is one of the most essential processes of life. Not only does it provide the means of transforming solar and chemical energy into a utilizable form for all living organisms, it also extends into a range of metabolic processes that support the life of a cell. Thus, it is of great interest to understand the physical basis of the rates and reduction potentials of these reactions. To identify the major determinants of reduction potentials in redox proteins, we have chosen the simplest electron transfer protein, rubredoxin, a small (52-54 residue) iron-sulfur protein family, widely distributed in bacteria and archaea. Rubredoxins can be grouped into two classes based on the correlation of their reduction potentials with the identity of residue 44; those with Ala44 (ex: Pyrococcus furiosus) have reduction potentials that are ∼50 mV higher than those with Va144 (ex: Clostridium pasteurianum). Based on the crystal structures of rubredoxins from C. pasteurianum and P. furiosus, we propose the identity of residue 44 alone determines the reduction potential by the orientation of the electric dipole moment of the peptide bond between 43 and 44. Based on 1.5 $\AA$ resolution crystal structures and molecular dynamics simulations of oxidized and reduced rubredoxins from C. pasteurianum, the structural rearrangements upon reduction suggest specific mechanisms by which electron transfer reactions of rubredoxin should be facilitated.

  • PDF

Co-Electrodeposition of Bilirubin Oxidase with Redox Polymer through Ligand Substitution for Use as an Oxygen Reduction Cathode

  • Shin, Hyo-Sul;Kang, Chan
    • Bulletin of the Korean Chemical Society
    • /
    • v.31 no.11
    • /
    • pp.3118-3122
    • /
    • 2010
  • The water soluble redox polymer, poly(N-vinylimidazole) complexed with Os(4,4'-dichloro-2,2'-bipyridine)$_2Cl]^+$ (PVI-[Os(dCl-bpy)$_2Cl]^+$), was electrodeposited on the surface of a glassy carbon electrode by applying cycles of alternating square wave potentials between 0.2 V (2 s) and 0.7 V (2 s) to the electrode in a solution containing the redox polymer. The coordinating anionic ligand, $Cl^-$ of the osmium complex, became labile in the reduced state of the complex and was substituted by the imidazole of the PVI chain. The ligand substitution reactions resulted in crosslinking between the PVI chains, which made the redox polymer water insoluble and caused it to be deposited on the electrode surface. The deposited film was still electrically conducting and the continuous electrodeposition of the redox polymer was possible. When cycles of square wave potentials were applied to the electrode in a solution of bilirubin oxidase and the redox polymer, the enzyme was co-electrodeposited with the redox polymer, because the enzymes could be bound to the metal complexes through the ligand exchange reactions. The electrode with the film of the PVI-[Os(dCl-bpy)$_2Cl]^+$ redox polymer and the co-electrodeposited bilirubin oxidase was employed for the reduction of $O_2$ and a large increase of the currents was observed due to the electrocatalytic $O_2$ reduction with a half wave potential at 0.42 V vs. Ag/AgCl.

A Study on the Effect of Cellulose on Degradation Rate of Carbofuran in Flooded Paddy Soil (Carbofuran의 토양중 분해에 대한 Cellulose의 영향에 관한 연구)

  • Tu, Ock-Ju;Chung, Moon-Ho
    • Journal of Environmental Health Sciences
    • /
    • v.23 no.4
    • /
    • pp.97-103
    • /
    • 1997
  • Carbofuran was incubated for four weeks in three differenf types of paddy soil samples at 25$\circ$C. The soil samples prepared in the present study were as follows: control soil, 3% cellulose added soil and 10% cellulose added soil. The degradation rate of carbofuran significantly decreased by the addition of cellulose to soil(p<0.05). The initial pH of soils was 5.0. After incubation for four weeks, the pH of 10% cellulose added soil sample was lower than those of control soil and 3% cellulose added soil. According to increased organic carbon content of the soil, redox potentials of soils decreased. The decreased degradation rate of carbofuran in 10% cellulose added soil was related to the highly negative redox potentials in contrast with the oxidised conditions of control soil and 3% cellulose added soil.

  • PDF

Effects of Ionizable Groups on the Redox Potentials of Cytochrome c₃from D. vulgaris Miyazaki F

  • 박장수;강신원
    • Bulletin of the Korean Chemical Society
    • /
    • v.17 no.9
    • /
    • pp.820-826
    • /
    • 1996
  • The p2H dependence of the NMR chemical shifts of the proton signals of heme methyl groups and ionizable groups in the vicinity of the heme were investigated. The p2H titration of heme methyl signals in four macroscopic oxidation states by saturation tranfer method was performed in the range between p2H 5.2 and 9.0. While the p2H dependence of the heme methyl resonance in fully oxidized state was small, most resonances in the intermediate oxidation states showed certain shifts. Particularly, methyl resonances of heme 1 (sequential heme numbering) exhibited sharp p2H dependence in acidic range. β-CH2 of the propionate of hemes 1 and 4 were titrated in the range of p2H 4.5-9.0. Only the 6-propionate group of heme 1 was protonated in this p2H range and its titration curve was similar to those of methyl resonances of heme 1 in intermediate oxidation states. Analysis of the microscopic redox potentials showed that they change depending on p2H. The ionizable groups responsible for the p2H dependence of these potentials are 6-propionate of heme 1 in acidic range and His 67 in basic range.

  • PDF

Electrochemical Property of Immobilized Spinach Ferredoxin on HOPG Electrode

  • Nam Yun-Suk;Kim, You-Sung;Shin, Woon-Sup;Lee, Won-Hong;Choi, Jeong-Woo
    • Journal of Microbiology and Biotechnology
    • /
    • v.14 no.5
    • /
    • pp.1043-1046
    • /
    • 2004
  • The stability and electrochemical properties of a self-assembled layer of spinach ferredoxin on a quartz substrate and on a highly oriented pyrolytic graphite electrode were investigated. To fabricate the ferredoxin self-assembly layer, dimyristoylphosphatidylcholine was first deposited onto a substrate for ferredoxin immobilization. Surface analysis of the ferredoxin layer was carried out by atomic force microscopy to verify the ferredoxin immobilization. To verify ferredoxin immobilization on the lipid layer and to confirm the maintenance of redox activity, absorption spectrum measurement was carried out. Finally, cyclic-voltammetry measurements were performed on the ferredoxin layers and the redox potentials were obtained. The redox potential of immobilized ferredoxin had a formal potential value of -540 mV. It is suggested that the redox-potential measurement of self-assembled ferredoxin molecules could be used to construct a biosensor and biodevice.

Redox Potential of a Soybean Ferric Leghemoglobin Reductase

  • Kim, Hyun-Mi
    • BMB Reports
    • /
    • v.31 no.5
    • /
    • pp.444-452
    • /
    • 1998
  • The visible spectra of soybean ferric leghemoglobin reductase exhibited a charge transfer band at 530 nm under aerobic condition. Spectra of the oxidized enzyme show a flavin peak at 454 nm and the enzyme has three redox states associated with the active site of the enzyme. The enzyme has an active disulfide bridge and two-electron transfer may dominate in the ferric state of leghemoglobin reduction. The midpoint potentials of the enzyme were determined by spectrotitration to be -0.294 V for disulfide/dithiol and -0.318 V for FAD/$FADH_2$. Since the midpoint potentials for $NAD^+$/NADH and the ferrous/ferric states of leghemoglobin are -0.32 V and +0.22 V, respectively, it is proposed that two electrons are transferred sequentially from NADH to FAD, to the disulfide group, and then to the ferric state of leghemoglobin in the enzyme reaction.

  • PDF

Direct Acid Leaching of Zinc from Marmatite Ores 3 Acid Leaching of Marmatite Ores and the Electrode Potential Behavior of Sulfides (Marmatite 鑛의 直接酸浸出에 關한 硏究 (第3報) Marmatite 鑛의 酸浸出과 黃化物의 電極電位에 關한 硏究)

  • Kim Jae Won
    • Journal of the Korean Chemical Society
    • /
    • v.11 no.1
    • /
    • pp.38-43
    • /
    • 1967
  • In order to explain the positive catalytic action of copper compound for the rate of leaching of zinc sulfide minerals, the electrode and redox potentials of both synthetic and natural sulfides were measured at various conditions of temperatures and pressures. The potentials of Chalcopyrite and copper sulfide were considerably higher than that of zinc sulfide, whereas lead sulfide and Galena had slightly lower potentials than that of zinc sulfide. At elevated temperatures and pressures, the same tendency was obtained. By means of comparing the calculated and measured values of potentials for sulfides, it was suggested that the electrode potentials in acid solution were generated by oxidation of sulfur ion. As a result, it was concluded that the catalytic action of copper compound in the leaching of synthetic zinc sulfide should be arised from the galvanic action between sulfides keeping intimate contact one another in which copper sulfide worked as cathodic and zinc sulfide as anodic part analogous to the metal corrosion under galvanic action.

  • PDF

Assignment of the Redox Potentials of Cytochrome c₃of Desulfovibrio vulgaris Hildenborough by ¹H NMR

  • 박장수;강신원;신정휴
    • Bulletin of the Korean Chemical Society
    • /
    • v.16 no.10
    • /
    • pp.968-971
    • /
    • 1995
  • The heme assignment of the 1H NMR spectrum of cytochrome c3 of Desulfovibrio vulgaris Hildenborough within the X-ray structure were fully cross established according to their redox potential. The major reduction of the heme turned out to take place in the order of hemes Ⅳ,Ⅰ,Ⅱ and Ⅲ(the heme numbers indicating the order of bonding to the primary sequence). This assignment can provide the physicochemical basis for the elucidation of electron transfer of this protein.

  • PDF