Monday, January 17, 2011

17O Central Transition NMR

A nice write-up of Gang Wu's solution 17O central transition NMR studies of biomolecules can be found in C&E News

The corresponding articles are:

Quadrupole Central Transition 17O NMR Spectroscopy of Biological Macromolecules in Aqueous Solution

Jianfeng Zhu and Gang Wu*

J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/ja1079207

Abstract: We demonstrate a general nuclear magnetic resonance (NMR) spectroscopic approach in obtaining high-resolution 17O (spin-5/2) NMR spectra for biological macromolecules in aqueous solution. This approach, termed quadrupole central transition (QCT) NMR, is based on the multiexponential relaxation properties of half-integer quadrupolar nuclei in molecules undergoing slow isotropic tumbling motion. Under such a circumstance, Redfield’s relaxation theory predicts that the central transition, mI = +1/2 ↔ −1/2, can exhibit relatively long transverse relaxation time constants, thus giving rise to relatively narrow spectral lines. Using three robust protein−ligand complexes of size ranging from 65 to 240 kDa, we have obtained 17O QCT NMR spectra with unprecedented resolution, allowing the chemical environment around the targeted oxygen atoms to be directly probed for the first time. The new QCT approach increases the size limit of molecular systems previously attainable by solution 17O NMR by nearly 3 orders of magnitude (1000-fold). We have also shown that, when both quadrupole and shielding anisotropy interactions are operative, 17O QCT NMR spectra display an analogous transverse relaxation optimized spectroscopy type behavior in that the condition for optimal resolution depends on the applied magnetic field. We conclude that, with the currently available moderate and ultrahigh magnetic fields (14 T and higher), this 17O QCT NMR approach is applicable to a wide variety of biological macromolecules. The new 17O NMR parameters so obtained for biological molecules are complementary to those obtained from 1H, 13C, and 15N NMR studies.

Solid-State 17O NMR Spectroscopy of Large Protein–Ligand Complexes†
Dr. Jianfeng Zhu1, Dr. Eric Ye2, Dr. Victor Terskikh3, Prof. Dr. Gang Wu1
Article first published online: 29 OCT 2010

DOI: 10.1002/anie.201002041

Angewandte Chemie International Edition
Volume 49, Issue 45, pages 8399–8402, November 2, 2010

oxygen-17;protein–ligand interactions;proteins;solid-state NMR spectroscopy;structure refinement

Oxygen, oxygen, everywhere! Poor sensitivity has hindered the development of solid-state 17O NMR spectroscopy as a practical technique for the structural elucidation of protein complexes. However, this has now changed and it has been demonstrated that multinuclear 17O, 27Al, 13C NMR parameters can be used to aid structural refinement for a protein-bound ligand molecule (see picture).

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