Obtaining ligand geometries from paramagnetic shifts in low-spin haem proteins |
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Authors: | David L Turner |
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Institution: | (1) Department of Chemistry, University of Southampton, Southampton SO17 1BJ, UK e-mail: dlt@soton.ac.uk Tel.: +44-2380-593330 Fax: +44-2380-593781, GB |
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Abstract: | b and c with His, Met, and cyanide ligands. Variations in the electronic structure of the haem and the magnetic susceptibility tensors
have been shown to depend primarily on the axial ligand geometry, and the shifts of haem substituents have been used to obtain
the first structural information for several cytochromes. Recently, the database of assigned spectra for bis-His haems has
been extended sufficiently for an empirical equation to be produced for treating 1H NMR data from haem methyl groups at 298 K. However, the database used contains large systematic deviations and the form
of the equation leads to systematic errors in the ligand geometries. This article describes the link with the semi-empirical
methods used previously and provides a set of corrected empirical parameters as well as an improved equation. The possibilities
for generalising the empirical method to account for ligands other than His and temperatures other than 298 K are discussed.
Received: 19 October 1999 / Accepted: 21 February 2000 |
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Keywords: | Haem protein Nuclear magnetic resonance Paramagnetic shift Ligand geometry |
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