Ferrocyanide − a novel catalyst for oxymyoglobin oxidation by molecular oxygen

Abstract

A comparative study of the rates of ferrocyanide‐catalyzed oxidation of several oxymyoglobins by molecular oxygen is reported. Oxidation of the native oxymyoglobins from sperm whale, horse and pig, as well as the chemically modified (MbO2) sperm whale oxymyoglobin, with all accessible His residues alkylated by sodium bromoacetate (CM‐MbO2), and the mutant sperm whale oxymyoglobin [MbO2(His119→Asp)], was studied. The effect of pH, ionic strength and the concentration of anionic catalyst ferrocyanide, [Fe(CN)6]4–, on the oxidation rate is investigated, as well as the effect of MbO2 complexing with redox‐inactive Zn2+, which forms the stable chelate complex with functional groups of His119, Lys16 and Asp122, all located nearby. The catalytic mechanism was demonstrated to involve specific [Fe(CN)6]4– binding to the protein in the His119 region, which agrees with a high local positive electrostatic potential and the presence of a cavity large enough to accommodate [Fe(CN)6]4– in that region. The protonation of the nearby His113 and especially His116 plays a very important role in the catalysis, accelerating the oxidation rate of bound [Fe(CN)6]4– by dissolved oxygen. The simultaneous occurrence of both these factors (i.e. specific binding of [Fe(CN)6]4– to the protein and its fast reoxidation by oxygen) is necessary for the efficient ferrocyanide‐catalyzed oxidation of oxymyoglobin.

Oxidation of 8-Oxo-7,8-dihydro-2′-deoxyguanosine Leads to Substantial DNA-Histone Cross-Links within Nucleosome Core Particles

“…However, this is unlikely given that these mutations in the H4 N-terminal tail have been demonstrated to bring about insignificant influence on the “601” NCP structure. , Another explanation is that the positively charged tail chelates Fe­(CN) 6 3– through electrostatic interaction and enhances the oxidation rate by increasing the effective concentration of the oxidant. Protein promoted oxidation by Fe­(CN) 6 3– has been observed previously …”

“…Protein promoted oxidation by Fe(CN) 6 3− has been observed previously. 52 Deleting the N-terminal tail (1−20 residues, Del 1−20) also significantly reduced the DPC formation efficiency (E DPC ) from 0.97 to 0.33 (Table 1). This result corroborates the prior evidence that the lysine-rich N-terminal tail of H4 is responsible for DPC formation with OG ox 89 .…”

The Glutathione/Metallothionein System Challenges the Design of Efficient O2‐Activating Copper Complexes

“…Experimentalc onditions: preformed copper complexesCuL 1/2 5 mMc oncentration, AscH À 100 mM, in HEPES 50 mM, pH 7.4. % 20 min 0.10 AE 0.06 À0.14 [33] Cu II -gtsm % 50 min 0.49 AE 0.10 À0.24 [29] Cu II -Dp44mT % 4min 0.92 AE 0.11 À0.21 [34] Cu II -(5,5'-DmBipy) 2 < 30 sec 10.1 AE 1.0 0.12 [35] Cu II -(Phen) 2 < 30 sec 12.4 AE 1.7 0.17 [35] Cu I -(BCS) 2 < 30 sec 0.07 AE 0.01 0.62 [36] Angewandte Chemie…”

Magnetic field alignment of stable proton-conducting channels in an electrolyte membrane

“…This complex would be effective in realizing both TP magnetic alignment and PWA retention, and concurrently maintain proton conductivity, as both CP4VP and PWA are proton conductive. The redox reaction of CP4VP derives from transitions between ferrocyanide (Fe(II)) and ferricyanide (Fe(III)) 57,58 . Due to the strongly negative charge on this redox couple, it would be capable of continuously consuming electrophilic OH • and OOH • radicals during the redox process, thus helping to shield other regions of the PEM structure.…”