title: Multi-dimensional NMR without coherence transfer: minimizing losses in large systems.
abstract: Most multi-dimensional solution NMR experiments connect one dimension to another using coherence transfer steps that involve evolution under scalar couplings. While experiments of this type have been a boon to biomolecular NMR the need to work on ever larger systems pushes the limits of these procedures. Spin relaxation during transfer periods for even the most efficient (15)N-(1)H HSQC experiments can result in more than an order of magnitude loss in sensitivity for molecules in the 100 kDa range. A relatively unexploited approach to preventing signal loss is to avoid coherence transfer steps entirely. Here we describe a scheme for multi-dimensional NMR spectroscopy that relies on direct frequency encoding of a second dimension by multi-frequency decoupling during acquisition, a technique that we call MD-DIRECT. A substantial improvement in sensitivity of (15)N-(1)H correlation spectra is illustrated with application to the 21 kDa ADP ribosylation factor (ARF) labeled with (15)N in all alanine residues. Operation at 4°C mimics observation of a 50 kDa protein at 35°C.
authors.affiliation: Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602, USA.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Liu
authors.forename: James H
authors.initials: JH
authors.lastname: Prestegard
mesh_terms: D000465:Algorithms; D005583:Fourier Analysis; D016014:Linear Models; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009587:Nitrogen Isotopes; D011522:Protons; D059629:Signal-To-Noise Ratio
chemical_list: D009587:Nitrogen Isotopes; D011522:Protons