Kinetic isotope effects from QM/MM subset hessians: "Cut-off" analysis for SN2 methyl transfer in solution

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)
179 Downloads (Pure)


Isotopic partition-function ratios and kinetic isotope effects for reaction of S-adenosylmethionine with catecholate in water are evaluated using a subset of 324 atoms within its surrounding aqueous environment at the AM1/TIP3P level. Two alternative methods for treating motion in the six librational degrees of freedom of the subset atoms relative to their environment are compared. A series of successively smaller subset Hessians are generated by cumulative deletion of rows and columns from the initial 972 X 972 Hessian. We find that it is better to treat these librations as vibrations than as translations and rotations and that there is no need to invoke the Teller-Redlich product rule. The validity of "cut-off" procedures for computation of isotope effects with truncated atomic subsets is assessed: to ensure errors in ln(KIE) < 1% (or 2% for the quantum-corrected KIE) for all isotopic substitutions considered, it is necessary to use a less-restrictive procedure than is suggested by the familiar two-bond cutoff rule.
Original languageEnglish
Pages (from-to)542-553
Number of pages12
JournalJournal of Chemical Theory and Computation
Issue number2
Early online date7 Jan 2012
Publication statusPublished - 14 Feb 2012

Fingerprint Dive into the research topics of 'Kinetic isotope effects from QM/MM subset hessians: "Cut-off" analysis for S<sub>N</sub>2 methyl transfer in solution'. Together they form a unique fingerprint.

Cite this