How does pressure affect barrier compression and isotope effects in an enzymatic hydrogen tunneling reaction?

Promoting vibrations-sub-ps donor-acceptor compressive modes in H-transfer reactions-cannot be directly observed experimentally. By using molecular dynamics simulations, an enzymic promoting vibration was identified that becomes stiffer with increasing pressure. This result explains previously observed changes in the rate and kinetic isotope effect for this enzyme-catalyzed H-transfer (see picture; NADH=nicotinamide adenine dinucleotide, FMN=flavin mononucleotide). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.