Continuum Simulations of Acetylcholine Consumption by Acetylcholinesterase: A Poisson-Nernst-Planck Approach

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• 作者：Y. C. Zhou ; Benzhuo Lu ; Gary A. Huber ; Michael J. Holst ; J. Andrew McCammon
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：January 17, 2008
• 年：2008
• 卷：112
• 期：2
• 页码：270 - 275
• 全文大小：346K
• 年卷期：v.112,no.2(January 17, 2008)
• ISSN：1520-5207

文摘

The Poisson-Nernst-Planck (PNP) equation provides a continuum description of electrostatic-driven diffusionand is used here to model the diffusion and reaction of acetylcholine (ACh) with acetylcholinesterase (AChE)enzymes. This study focuses on the effects of ion and substrate concentrations on the reaction rate and ratecoefficient. To this end, the PNP equations are numerically solved with a hybrid finite element and boundaryelement method at a wide range of ion and substrate concentrations, and the results are compared with thepartially coupled Smoluchowski-Poisson-Boltzmann model. The reaction rate is found to depend stronglyon the concentrations of both the substrate and ions; this is explained by the competition between theintersubstrate repulsion and the ionic screening effects. The reaction rate coefficient is independent of thesubstrate concentration only at very high ion concentrations, whereas at low ion concentrations the behaviorof the rate depends strongly on the substrate concentration. Moreover, at physiological ion concentrations,variations in substrate concentration significantly affect the transient behavior of the reaction. Our resultsoffer a reliable estimate of reaction rates at various conditions and imply that the concentrations of chargedsubstrates must be coupled with the electrostatic computation to provide a more realistic description ofneurotransmission and other electrodiffusion and reaction processes.