The ionic strength dependence of the rate of a reaction between two large proteins with a dipole moment

Leeuwen, Johan W. van

doi:10.1016/0167-4838(83)90400-4

Cited by 66 publications

(77 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%

“…Analyses involving both point charges and dipole moments also require the use of net charges (Koppenol, 1980;Van Leeuwen et aI., 1981;Van Leeuwen, 1983). For some protein systems, these analyses have provided reasonable agreement between the calculated and expected net charges (Feinberg & Ryan, 1981), whereas in other examples the analysis fails to predict either the sign or the magnitude of the interaction, or both, and the data can only be rationalized using parameters that reflect the localized charge distribution near the active site (Hammes & Alberty, 1959;Rickle & Cusanovich, 1979;Stonehuerner et al, 1979;Simondsen et al, 1982).…”

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“…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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