Water-macromolecule interactions by NMR: a quadrature-free constant-time approach and its application to CI2.
A pulse sequence is proposed to select water magnetization with enhanced specificity through a synergetic combination of several filtering principles. This approach relies on a constant-time evolution period implemented without quadrature detection, which results in a square root 2 increase in signal-to-noise ratios as compared to traditional non-selective methods for water filtration. In addition, the quadrature-free constant-time block facilitates the implementation of the water flip-back strategy, which leads to further gains in sensitivity. The proposed experiment was applied to unlabeled HEW lysozyme and to 15N-labeled chymotrypsin inhibitor 2 which was partially or non 13C-enriched. Water molecules belonging to a spine of hydration between two pseudo beta-sheet strands were identified, solving previously reported discrepancies between the X-ray and refined NMR structure of CI2. The proposed experiment in particularly suitable for hydration studies of mixtures of labeled and unlabeled components, such as ligand-macromolecule complexes.
Melacini
G
G
NMR Department, Bijvoet Center for Biomolecular Research, Utrecht University, The Netherlands.
Boelens
R
R
Kaptein
R
R
D006860:Hydrogen Bonding; D046911:Macromolecular Substances; D009113:Muramidase / Q000737:chemistry / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000295:instrumentation / Q000379:methods*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010940:Plant Proteins; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D011522:Protons; D015203:Reproducibility of Results; D014867:Water / Q000378:metabolism*
D046911:Macromolecular Substances; D010455:Peptides; D010940:Plant Proteins; D011506:Proteins; D011522:Protons; C093336:chymotrypsin inhibitor 2; D014867:Water; D009113:Muramidase