Web Release Date: August 28,
Molecular Recognition and Screening Using a 15N Group Selective STD NMR Method
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Contribution from the Department of Inorganic and Analytical Chemistry and Department of Biochemistry, Centre of Arts, Humanities and Sciences, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary, School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, and Department of Protein Science, Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
Received May 18, 2007
Abstract:
We present a novel saturation transfer difference (STD) experiment where group selective (GS) saturation of amide protons in 15N labeled hosts is achieved. It is demonstrated that a train of BIRDd pulses that inverts only protons attached to 15N indeed results in saturation of the amide protons, while the background proton magnetization is much less affected. The undesired effect of partial saturation of the unlabeled protons can be completely cancelled out in difference spectra by switching the 15N carrier between the on- and the off-resonance frequencies. As a result, clean and artifact-free STD spectra are obtained without the need of time-consuming optimization of experimental parameters and acquiring control spectra in the absence of the host. The use of the 15N-GS STD experiment is demonstrated for the case of a glycopeptide antibiotic (dimeric eremomycin)-cell-wall analogue peptide (N-Ac-D-Ala) model system where the host and guest 1H signals overlap. The application seems feasible for ligand screening against proteins without the prerequisite of a clean on-resonance frequency or defined ligand library. The new experiment can be used as the basis for studying intermolecular interactions where the standard STD experiment is difficult to optimize.
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