Selective heteronuclear Hartmann-Hahn: a multiple-pulse sequence for selective magnetization transfer in the structural elucidation of "isotagged" oligosaccharides.
A new selective heteronuclear Hartmann-Hahn (SHEHAHA) multiple-pulse mixing sequence is proposed for the solution structure elucidation of milligram amounts of peracetylated oligosaccharides in which the acetyl groups are enriched in carbon-13, so-called "isotags". SHEHAHA accomplishes exclusive in-phase magnetization transfer between the isotag carbonyl (13)C and the proximal proton on the sugar ring. Relayed transfer around the sugar rings by proton-proton TOCSY is suppressed, while the heteronuclear transfer from the labeled carbonyl carbon to the proximal ring proton is maintained. The sequence is broadband in the sense that all acetyl groups simultaneously give good signal transfer to their respective nearest proton neighbors. The (1)H-detected spectra have decent sensitivity and excellent resolution, giving patterns that unambiguously identify common structural subunits in human glycans. Peracetylated maltitol is shown as a test case of the method. Lineshapes are pure absorption, allowing facile measurement of vicinal proton-proton couplings. Linkage points can be deduced, and the 2D correlation spectra may be useful for more ambitious prediction algorithms and machine identification by a spectral database.
Meng
Xi
X
Department of Chemistry, University of California, Irvine, CA 92697-2025, USA.
Nguyen
William H
WH
Nowick
James S
JS
Shaka
A J
AJ
D000107:Acetylation; D000465:Algorithms; D002138:Calibration; D002236:Carbohydrate Conformation; D004574:Electromagnetic Fields; D006801:Humans; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008698:Mesylates; D009844:Oligosaccharides / Q000032:analysis*; D011134:Polysaccharides / Q000737:chemistry; D011522:Protons; D011846:Radio Waves; D012538:Scandium; D012997:Solvents
D007202:Indicators and Reagents; D008698:Mesylates; D009844:Oligosaccharides; D011134:Polysaccharides; D011522:Protons; D012997:Solvents; C436603:scandium triflate; D012538:Scandium