With the description of more and more complex one- and two-dimensional NMR experiments comes the need to develop methods to make a comprehensive interpretation of the various different experiments that can be carried out on the same sample or series of related samples. We present some examples of modelling one- and two-dimensional solid-state NMR spectra of I = ½ spin and quadrupolar nuclei, using laboratory-developed software that is made available to the NMR community. Copyright © 2001 John Wiley & Sons, Ltd.

Modelling one- and two-dimensional solid-state NMR spectra†

Chemistry of zirconia and its use in chromatography

Structural characterization of noncrystalline solids and glasses using solid state NMR

Mesoscopically ordered, transparent silica-surfactant monoliths have been prepared using amphiphilic triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) copolymer species to organize polymerizing silica networks. The block copolymer acts as a structure- directing agent, as the aqueous silica cations partition within the hydrophilic regions of the self-assembled system and associate preferentially with the PEO blocks. Subsequent polymerization of the silica precursor species under strongly acidic conditions (pH 1) produces a densely cross-linked silica network that may be mesoscopically organized by the block copolymer species into composites with characteristic ordering length scales of >10 nm. When this is accompanied by slow evaporation of the aqueous solvent, such composite mesostructures can be formed into transparent and crack-free monoliths (e.g., 2.5 cm diameter 3 mm thick). Distributions and dynamics of the PEO and PPO copolymer blocks within the silica matrix were investigated in situ using 29 Si{ 1 H} and 13 C{ 1 H} two-dimensional solid-state heteronuclear correlation NMR techniques and 1 H NMR relaxation measurements. Mesostructural ordering was determined by X-ray diffraction and transmission electron microscopy. The degree of microphase separation and the resulting mesostructure of bulk samples were found to depend strongly upon the concentration of block copolymer, with higher concentrations producing higher degrees of order.

Molecular and Mesoscopic Structures of Transparent Block Copolymer-Silica Monoliths

Magainin2 is a 23-residue antibiotic peptide that disrupts the ionic gradient across certain cellmembranes. Two-dimensional 1H NMR spectroscopy was used to investigate the structure ofthe peptide in three of the membrane environments most commonly employed in biophysicalstudies. Sequence-specific resonance assignments were determined for the peptide inperdeuterated dodecylphosphocholine (DPC) and sodium dodecylsulfate micelles andconfirmed for the peptide in 2,2,2-trifluoroethanol solution. The secondary structure is shownto be helical in all of the solvent systems. The NMR data were used as a set of restraints fora simulated annealing protocol that generated a family of three-dimensional structures of thepeptide in DPC micelles, which superimposed best between residues 4 and 20. For theseresidues, the mean pairwise rms difference for the backbone atoms is 0.47 ± 0.10A from the average structure. The calculated peptide structures appear to be curved,with the bend centered at residues Phe12 and Gly13.

Two-dimensional 1H NMR experiments show that the 23-residue magainin antibiotic peptide is an alpha-helix in dodecylphosphocholine micelles, sodium dodecylsulfate micelles, and trifluoroethanol/water solution.

M. E. Smith

Papers

Solid-State NMR