The ionic strength dependence of the rate of a reaction between a small ion and a large ion with a dipole moment

Leeuwen, Johan W. van; Mofers, Frans J.M.; Veerman, E.C.I.

doi:10.1016/0005-2728(81)90041-4

Cited by 30 publications

(26 citation statements)

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“…Attempts to theoretically describe the dependence of bimolecular rate constants on ionic strength for small molecules have generally relied on Debye-Huckel theory to estimate the electrostatic forces (Debye & Hiickel, 1923; Debye, 1942), and Bronsted, Marcus, Koppenol, 1980; Van Leeuwen et al, 1981; Van Leeuwen, 1983). The fundamental feature of these approaches is the use of a potential energy function for a small uniformly reactive molecule, in which the potential energy is described by 2 point charges or di-poles in a spherical cavity.…”

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confidence: 99%

“…Extrapolation of the observed rate constants to infinite ionic strength gives the electrostatically corrected diffusion-controlled rate constant (Amis & Van Leeuwen et al, 1981; Van Leeuwen, 1983), usually referred to as k,. Such extrapolations have been used to determine electron transfer rate constants according to the extended Marcus theory formulation of Wherland and Gray (1976).…”

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confidence: 99%

“…Such extrapolations have been used to determine electron transfer rate constants according to the extended Marcus theory formulation of Wherland and Gray (1976). Extrapolation to zero ionic strength gives the rate constant for bimolecular complex forma-tion under conditions in which the effects of electrostatic forces between charged reactant molecules are maximized (Alberty & Hammes, 1958;Van Leeuwen et al, 1981;Van Leeuwen, 1983).…”

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confidence: 99%

“…Additionally, when net protein charges and molecular radii are used, rate constants at zero ionic strength determined from extrapolation of model fits to the data are often found to yield values much larger than the diffusion rate constant, IO'* M" s-' (Rickle & Cusanovich, 1979;Simondsen et al, 1982), which is theoretically impossible (Eigen, 1954). It is also important to note that none of the current approaches consider localized charges except in terms of dipolar interactions (Van Leeuwen et al, 1981;Van Leeuwen, 1983).…”

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A “parallel plate” electrostatic model for bimolecular rate constants applied to electron transfer proteins

et al. 1994

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A "parallel plate" model describing the electrostatic potential energy of protein-protein interactions is presented that provides an analytical representation of the effect of ionic strength on a bimolecular rate constant. The model takes into account the asymmetric distribution of charge on the surface of the protein and localized charges at the site of electron transfer that are modeled as elements of a parallel plate condenser. Both monopolar and dipolar interactions are included. Examples of simple (monophasic) and complex (biphasic) ionic strength dependencies obtained from experiments with several electron transfer protein systems are presented, all of which can be accommodated by the model. The simple cases do not require the use of both monopolar and dipolar terms (i.e., they can be fit well by either alone). The biphasic dependencies can be fit only by using dipolar and monopolar terms of opposite sign, which is physically unreasonable for the molecules considered. Alternatively, the high ionic strength portion of the complex dependencies can be fit using either the monopolar term alone or the complete equation; this assumes a model in which such behavior is a consequence of electron transfer mechanisms involving changes in orientation or site of reaction as the ionic strength is varied. Based on these analyses, we conclude that the principal applications of the model presented here are to provide information about the structural properties of intermediate electron transfer complexes and to quantify comparisons between related proteins or site-specific mutants. We also conclude that the relative contributions of monopolar and dipolar effects to protein electron transfer kinetics cannot be evaluated from experimental data by present approximations.

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A “parallel plate” electrostatic model for bimolecular rate constants applied to electron transfer proteins

et al. 1994

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“…The values of the second-order rate constants extrapolated to infinite ionic strength (k;) provided a measure of the intrinsic reactivity of the two proteins to the oxidant (van Leeuwen et al, 1981). The k; values obtained in this way revealed 7: vaginalis ferredoxin to be more than two orders of magnitude more reactive than Anabaena ferredoxin ( Table 4).…”

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confidence: 99%

Electrostatic effects in electron transfer reactions of [2Fe‐2S] ferredoxins with inorganic reagents

Vidakovic

Germanas

1996

Protein Science

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The kinetics of electron transfer from the reduced [2Fe-2S] ferredoxins from the cyanobacterium Anabaena 7120 and the protozoan Trichomonas vaginalis to select cobalt coordination compounds have been studied in order to gain insight into the mechanism of electron transfer and intrinsic reactivity of [2Fe-2S] active sites. With tripositive cobalt complexes, reactions of both proteins displayed saturation kinetics; values of association constants of 12,900 and 1,400 M-I and limiting rate constants of 7.6 and 3.5 s" were found for oxidation of I: vaginalis and Anabaena ferredoxins, ferredoxin is more accessible and adjacent to a less highly charged, more compact patch of negative charges than the photosynthetic protein.

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4-Nitroimidazole Binding to Horse Metmyoglobin: Evidence for Preferential Anion Binding

Taylor

Vitello

Erman

2000

Archives of Biochemistry and Biophysics

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The ionic strength dependence of the rate of a reaction between a small ion and a large ion with a dipole moment

Cited by 30 publications

References 8 publications

A “parallel plate” electrostatic model for bimolecular rate constants applied to electron transfer proteins

A “parallel plate” electrostatic model for bimolecular rate constants applied to electron transfer proteins

Electrostatic effects in electron transfer reactions of [2Fe‐2S] ferredoxins with inorganic reagents

4-Nitroimidazole Binding to Horse Metmyoglobin: Evidence for Preferential Anion Binding

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