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Journal of Biomolecular NMR

, Volume 44, Issue 3, pp 119–126

First Online: 20 May 2009Received: 14 January 2009Accepted: 06 April 2009

Abstract

Quantum mechanical calculations are presented that predict that one-bond deuterium isotope effects on the N chemical shift of backbone amides of proteins, ΔND, are sensitive to backbone conformation and hydrogen bonding. A quantitative empirical model for ΔND including the backbone dihedral angles, Φ and Ψ, and the hydrogen bonding geometry is presented for glycine and amino acid residues with aliphatic side chains. The effect of hydrogen bonding is rationalized in part as an electric-field effect on the first derivative of the nuclear shielding with respect to N–H bond length. Another contributing factor is the effect of increased anharmonicity of the N–H stretching vibrational state upon hydrogen bonding, which results in an altered N–H-N–D equilibrium bond length ratio. The N–H stretching anharmonicity contribution falls off with the cosine of the N–H···O bond angle. For residues with uncharged side chains a very good prediction of isotope effects can be made. Thus, for proteins with known secondary structures, ΔND can provide insights into hydrogen bonding geometries.

KeywordsProtein Hydrogen bond Isotope effect Backbone conformation Formamide Electric field effect Electronic supplementary materialThe online version of this article doi:10.1007-s10858-009-9316-0 contains supplementary material, which is available to authorized users.

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Autor: Jens Abildgaard - Poul Erik Hansen - Marlon N. Manalo - Andy LiWang

Fuente: https://link.springer.com/







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