Sample concentration and labelling
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What information from NMR can be obtained with that sample?
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unlabelled protein at low µM
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1D 1H spectra providing information on folding and the effects of solvent (pH, salt, etc.) and temperature, sample quality/reproducibility, ligand-detected small molecule screens (fast and quantitative), translational diffusion.
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unlabelled protein at 500 µM to 1 mM
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2D natural abundance 15N and 13C spectra to identify sample homogeneity, proportion of residues folded or flexible, some amino acid type specific information (e.g., glycines), greater information on sample quality and suitability for further studies; comparative studies become much more powerful – e.g., between different constructs (deletion or mutation) and different solvent conditions or with/without binding partners.
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15N or 13C labelled at 100-200 µM and above
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Essentially any of the experiments described in this document can be performed. Some experiments are more demanding with regard to sample concentration, notably the CPMG experiments for quantifying µs-ms timescale motions.
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Post-translationally labelled protein: protein expressed unlabelled and purified from any host, and then post-translationally labelled, typically by addition of 13C or 19F isotopes to lysines or cysteines.
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Monitoring conformational changes upon ligand binding, for example to identify and utilise spectral signatures or to screen for ligand binding; quantifying dynamics.
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