The Oxidation Potential of the System Potassium Ferrocyanide–Potassium Ferricyanide at Various Ionic Strengths

Kolthoff, I. M.; Tomsicek, William J.

doi:10.1021/j150367a004

Cited by 202 publications

(111 citation statements)

References 9 publications

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“…The redox potential of cytochrome c is independent of ionic strength around 0.1 M at neutral pH, with a value of 260 mV (13). The properties of the four reagents (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) to be discussed in detail are given in Table 1.…”

Section: Theorymentioning

confidence: 99%

Metalloprotein electron transfer reactions: analysis of reactivity of horse heart cytochrome c with inorganic complexes.

Wherland¹,

Gray²

1976

Proc. Natl. Acad. Sci. U.S.A.

115

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The reactions of horse heart cytochrome c with Fe(ethylenediaminetetraacetate)r, Co(1, It has been suggested previously that electron transfer between horse heart cytochrome c and certain inorganic redox agents takes place by an outer-sphere mechanism at the heme edge that is partially exposed at the protein surface (1-3). In a particularly striking example, the calculated protein self-exchange rate constant (k1) based on oxidation of ferrocytochrome c by Co(phen)33+ (phen = 1,10-phenanthroline) has been shown to be in good agreement with the measured value, suggesting that the crossreaction involves a very similar mechanism (2). It should not necessarily be expected, however, that all reagents will have equal access to the heme edge in solution, as examination of structural models reveals that hydrophobic residues surround it. Indeed, the degree of access to the heme edge needs to be determined for a variety of substrates of various sizes, charges, and surface properties.The purpose of this paper is to present a detailed analysis of the kinetics of the electron transfer reactions of cytochrome c with Fe(CN)O3, Ru(NH3)(j+, Co(phen)33+, and Fe(EDTA)2-(EDTA = ethylenediaminetetraacetate). We shall employ the Marcus theory of outer-sphere electron transfer reactions to compensate for the variation in driving force and inherent reactivity of the reagents. Special attention will be directed to the evaluation of the electrostatic interactions between the protein and each reagent, thereby allowing an estimate to be made of the magnitudes of nonelectrostatic contributions to the activation free energies for the reactions. THEORYThe Marcus theory correlates the crossreaction rate constant (k12) with the electron exchange rate constants for the two reactants (kil and k22) and the equilibrium constant (K) through the expressions k12 = (klk22Kf)/2 [1] phen, 1,10-log f = (log K)2/[4 log (kilk22/Z2)] [2] where the factor f is quite near 1 for the reactions to be considered here because they have rather small equilibrium constants (Z is the collision frequency) (4). With the inclusion of adiabaticity factors p, Eq. 1 becomes k12 = pI2(k11k22Kf/ p1Ip22)/2 (4). For the purposes of this treatment, it will be assumed that the reactions are adiabatic (Plu = P22 = P12 = 1), or at least uniformly nonadiabatic (p122 = PlIP22). Eq. 1 may.be applied as written, and the predicted kl2 value may be calculated from known values of ki1, k22, and K. In this approach, any deviation of the calculated from the observed values can be attributed to either the protein's or the reagent's undergoing a different activation process than in the self-exchange reaction, or to interaction energies between the reagent and protein which are not cancelled by the interactions in the exchange processes. Alternatively, it may be assumed that the activation process for reagent electron transfer, characterized by the exchange rate k22, is approximately a constant. Under this assumption Eq. 1 can be solved for kI, (the subscript 1 refers to the protein in ...

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Section: Theorymentioning

confidence: 99%

Metalloprotein electron transfer reactions: analysis of reactivity of horse heart cytochrome c with inorganic complexes.

Wherland¹,

Gray²

1976

Proc. Natl. Acad. Sci. U.S.A.

115

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“…In this experiment, an appropriate concentration of redox active species is dissolved into the aqueous continuous phase such that individual adsorption events can be distinguished from the background. Potassium ferrocyanide [K 4 Fe(CN) 6 , KFCN, E o = ∼0.24 V vs. Ag/AgCl], was chosen as the redox active species in this study because KFCN incompletely dissociates during dissolution (19)(20)(21) due to ion pairing (22). This incomplete dissociation is advantageous in solutions of colloidal suspensions because high ionic strength media will cause suspensions to aggregate.…”

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confidence: 99%

Electrochemical detection of a single cytomegalovirus at an ultramicroelectrode and its antibody anchoring

Dick

Hilterbrand

Boika

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

150

132

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We report observations of stochastic collisions of murine cytomegalovirus (MCMV) on ultramicroelectrodes (UMEs), extending the observation of discrete collision events on UMEs to biologically relevant analytes. Adsorption of an antibody specific for a virion surface glycoprotein allowed differentiation of MCMV from MCMV bound by antibody from the collision frequency decrease and current magnitudes in the electrochemical collision experiments, which shows the efficacy of the method to size viral samples. To add selectivity to the technique, interactions between MCMV, a glycoprotein-specific primary antibody to MCMV, and polystyrene bead "anchors," which were functionalized with a secondary antibody specific to the Fc region of the primary antibody, were used to affect virus mobility. Bead aggregation was observed, and the extent of aggregation was measured using the electrochemical collision technique. Scanning electron microscopy and optical microscopy further supported aggregate shape and extent of aggregation with and without MCMV. This work extends the field of collisions to biologically relevant antigens and provides a novel foundation upon which qualitative sensor technology might be built for selective detection of viruses and other biologically relevant analytes.collisions | cytomegalovirus | electrochemistry | murine cytomegalovirus | virus O ver the past decade, the study of discrete collision events on ultramicroelectrodes (UMEs) has gained attention due to the interest in understanding stochastic phenomena by electrochemistry. By observing the collisions of small particles, there is the possibility that information can be deduced that is not available in ensemble measurements. The electrochemical study of single collision events has been applied to a wide range of hard nanoparticles (NPs), which include metal, metal oxide, and organic NPs [platinum (1), silver (2), gold (3), nickel (4), copper (5), iridium oxide (6), cerium oxide (7), titanium oxide (8), silicon oxide (9), indigo (10), polystyrene (11), and relatively large aggregates of fullerene (12)]. Recently, collisions of soft particles have been investigated, such as toluene droplets (13) and liposomes (14). Also, collisions of toluene and tri-n-propylamine droplets were observed simultaneously by both electrochemical and electrogenerated chemiluminescent (ECL) measurements (15).Similarly, a variety of techniques have been developed to observe these collision events. The interested reader can consult the references for a discussion on each of the techniques used to observe stochastic events electrochemically: blocking (9, 13), electrocatalytic amplification (1), open circuit potential (16), droplet blocking/reactor (13,14), and ECL (15,17,18). The simplest and most reproducible method of observing collisions is a technique termed blocking, which is so named because particles, which are brought to the electrode by a diffusion-limited flux and/or electrophoretic migration, irreversibly adsorb (1) to the electrode surface, blocking the flux of red...

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“…As a consequence of anthropogenic inputs, the Fe-CN complexes ferrocyanide, [Fe II (CN) 6 ] 4− , and ferricyanide,…”

Section: Introductionmentioning

confidence: 99%

“…[Fe III (CN) 6 ] 3− , may be present in soil. Their occurrence is mainly due to the deposition of wastes originating from industrial processes such as coal gasification, pig Fe production, or paper recycling [1].…”

Section: Introductionmentioning

confidence: 99%

“…Their occurrence is mainly due to the deposition of wastes originating from industrial processes such as coal gasification, pig Fe production, or paper recycling [1]. In these wastes, Fe-CN complexes are mainly present as sparingly soluble compounds, for example, Fe 4 [Fe II (CN) 6 [2]. A further source is road salt, to which Na 4 [Fe II (CN) 6 ] or Fe 4 [Fe II (CN) 6 ] 3 are added as an anticaking agent [3].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mobility of Iron-Cyanide Complexes in a Humic Topsoil under Varying Redox Conditions

Rennert

Mansfeldt²

2009

Applied and Environmental Soil Science

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The potentially toxic Fe-CN complexes ferricyanide, [Fe III (CN) ) to which we added ferricyanide (20 mg l −1 ). We varied the redox potential (E H ) from −280 to 580 mV by using O 2 , N 2 and glucose. The decrease of E H led to decreasing concentrations of Fe-CN complexes and partial reductive dissolution of (hydrous) Fe and Mn oxides. The dynamics of aqueous Fe-CN concentrations was characterized by decreasing concentrations when the pH rose and the E H dropped. We attribute these dependencies to adsorption on organic surfaces, for which such a pH/E H behavior has been shown previously. Adsorption was reversible, because when the pH and E H changed into the opposite direction, desorption occurred. This study demonstrates the possible impact of soil organic matter on the fate of Fe-CN complexes in soil.

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The Oxidation Potential of the System Potassium Ferrocyanide–Potassium Ferricyanide at Various Ionic Strengths

Cited by 202 publications

References 9 publications

Metalloprotein electron transfer reactions: analysis of reactivity of horse heart cytochrome c with inorganic complexes.

Metalloprotein electron transfer reactions: analysis of reactivity of horse heart cytochrome c with inorganic complexes.

Electrochemical detection of a single cytomegalovirus at an ultramicroelectrode and its antibody anchoring

Mobility of Iron-Cyanide Complexes in a Humic Topsoil under Varying Redox Conditions

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