Installing a tag containing a paramagnetic metal ion on a protein can lead to large changes (pseudocontact shifts) in the resonances observed in NMR spectra. These are easily measured and contain valuable long-range structural information. The present work shows that a single tagging site furnished with different tags can be sufficient to localise atoms in proteins with high accuracy. In fact, this strategy works almost as well as the same number of tags distributed over multiple tagging sites.

This paper explores a method for determining the solution structure of a solvent-exposed polypeptide segment (the L3 loop), which is next to the active site of the penicillin-degrading enzyme IMP-1. Tagging three different sites on the protein with paramagnetic metal ions allowed positioning of the L3 loop with atomic resolution. It was found that the method was more robust when omitting data obtained with different metal ions if obtained with the same tag at the same tagging site.

Fluorine NMR was used to study the interaction between a proline-rich peptide and a SH3 domain using 4S- and 4R-fluorinated prolines whose potential as NMR probes has not been exploited yet. We present a comprehensive study addressing several aspects to be considered when using these residues as NMR probes, including relaxation and dynamics. We show that their conformational bias may be used to modulate the kinetics of protein binding to proline-rich motifs.

We describe a suite of experiments that exploit field-dependent relaxation measurements of four-spin transitions in methyl groups to characterise chemical exchange processes and which can be used as an alternative or complement to CPMG relaxation dispersion measurements. We show that these four-spin transitions benefit from the methyl TROSY effect and so provide a unique combination of slow intrinsic relaxation and high sensitivity to chemical exchange.

The Biological Magnetic Resonance Data Bank (BMRB) has been used to identify overall trends, for example, the relationship between chemical shift and backbone conformation. The BMRB archive has grown so that statistical outliers are sufficiently numerous to afford insights into unusual or unique structural features in proteins. We analyze amide proton chemical shift outliers to gain insights into the occurrence of hydrogen bonds between an amide NH and the p-pi cloud of aromatic sidechains.