title: Efficient acquisition of high-resolution 4-D diagonal-suppressed methyl-methyl NOESY for large proteins.
abstract: The methyl-methyl NOESY experiment plays an important role in determining the global folds of large proteins. Despite the high sensitivity of this experiment, the analysis of methyl-methyl NOEs is frequently hindered by the limited chemical shift dispersion of methyl groups, particularly methyl protons. This makes it difficult to unambiguously assign all of the methyl-methyl NOE crosspeaks using 3-D spectroscopy. The recent development of sparse sampling methods enables highly efficient acquisition of high-resolution 4-D spectra, which provides an excellent solution to resolving the degeneracy of methyl signals. However, many reconstruction algorithms for processing sparsely-sampled NMR data do not provide adequate suppression of aliasing artifacts in the presence of strong NOE diagonal signals. In order to overcome this limitation, we present a 4-D diagonal-suppressed methyl-methyl NOESY experiment specifically optimized for ultrasparse sampling and evaluate it using a deuterated, ILV methyl-protonated sample of the 42 kDa Escherichia coli maltose binding protein (MBP). Suppression of diagonal signals removes the dynamic range barrier of the methyl-methyl NOESY experiment such that residual aliasing artifacts in the CLEAN-reconstructed high-resolution 4-D spectrum can be further reduced. At an ultrasparse sampling rate of less than 1%, we were able to identify and unambiguously assign the vast majority of expected NOE crosspeaks between methyl groups separated by less than 5 Å and to detect very weak NOE crosspeaks from methyl groups that are over 7 Å apart.
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wen
authors.forename: Pei
authors.initials: P
authors.lastname: Zhou
authors.forename: Jihui
authors.initials: J
authors.lastname: Wu
mesh_terms: D000465:Algorithms; D016477:Artifacts; D004926:Escherichia coli / Q000737:chemistry; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D058619:Maltose-Binding Proteins / Q000737:chemistry; D008745:Methylation; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D047392:beta-Cyclodextrins / Q000737:chemistry
chemical_list: D007202:Indicators and Reagents; D058619:Maltose-Binding Proteins; D011506:Proteins; D011522:Protons; D047392:beta-Cyclodextrins