Understanding Cross-Boundary Events in ONIOM QM:QM' Calculations
2012 (English)In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 33, no 4, 406-415 p.Article in journal (Refereed) Published
QM:QM' models, where QM' is a fast molecular orbital method, offers advantages over standard quantum mechanics: molecular mechanics (QM:MM) models, especially in the description of charge transfer and mutual polarization between layers. The ONIOM QM:QM' scheme also allows for reactions across the layer boundary, but the understanding of these events is limited. To explain the factors that affect cross-boundary events, a set of proton transfer processes, including the acylation reaction in serine protease, have been investigated. For reactions inside out, that is, when a group breaks a bond in the high layer and forms a new bond with a group in the low layer, QM' methods that are overbinding relative to the QM method, for example, Hartree-Fock versus B3LYP, can severely overestimate the exothermicity of the reaction. This might lead to artificial reactivity across the QM:QM' boundary, a phenomenon called model escape. The accuracy for reactions that occur outside in, that is, when a group in the low layer forms a new bond with the high layer, is mainly determined by the QM' calculation. Cross-boundary reactions should generally be avoided in the present ONIOM scheme. Fortunately, a better understanding of these events makes it easy to design stable ONIOM QM:QM' models, for example, by choosing a proper model system. Importantly, an accurate description of cross-boundary reactions would open up possibilities to simulate chemical reactions without a priori limiting the reactivity in the design of the computational model. Challenges to implement a simulation scheme (ONIOM-XR) that can automatically handle chemical reactions between different layers are briefly discussed.
Place, publisher, year, edition, pages
2012. Vol. 33, no 4, 406-415 p.
multiscale modeling, reactivity, serine protease, hydrogen bonds, QM simulations
IdentifiersURN: urn:nbn:se:uu:diva-181239DOI: 10.1002/jcc.21982ISI: 000298955100006PubMedID: 22109102OAI: oai:DiVA.org:uu-181239DiVA: diva2:555466