2D solid-state NMR techniques

A 2D solid-state NMR technique has been presented that can be used to determine the N chemical shift and H- N dipolar coupling tensors in powder samples of polypeptides containing N isotopes at multiple sites. The magnitudes of the principal elements of the N CSA tensors and their orientations in the molecular frame for A-acetyl- A-L-Val- A-L-Leu (NAVL) and A-acetyl- A-D,L-Val (NAV) powder samples have been determined using this method. 

D solid-state NMR techniques, such as the 2D-TOSS pulse sequence [39], can allow the separation of isotropic and anisotropic chemical shift information over two dimensions, making it possible to distinguish individual carbon atoms under moderate magic angle spinning (MAS) conditions. 

For Zr, the most studied system, EXAFS and chemical reactivity studies were consistent with the formation of [(=SiO)3Zr-H] as the major surface species. More recent studies involving ID and 2D solid-state NMR techniques have firmly shown that it is in fact a 65 35 mixture of [(=SiO)3ZrH] and [(=SiO)2ZrH2] species. The latter species is formed through the reaction of the hydride intermediates with only one siloxane bridge (Scheme 17). 

Before describing some of the recent advances in ID and 2D solid-state NMR techniques and giving examples of their application to soft organic materials, we will briefly summarize the relevant quantum mechanics and spin interactions. We will not discuss the theory and the NMR interactions in a complete fashion, but rather give the reader an appreciation of the theoretical underpinnings of the experiments. It should be noted that all spin interactions in this section are written using Cartesian operators, in contrast to the use of spherical tensor operators often seen in the NMR fttera-ture. The interested reader can find more details in excellent NMR textbooks and reviews in Refs. [14,27,28]. 

Polyelectrolyte multilayers on silica colloids are investigated here using a combination of fast MAS and DQ solid-state NMR techniques. 2D DQ H NMR spectra of the bulk complex and the multilayer films are found to be similar, revealing complexation between the alternating layers of poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC). 

Various ID and 2D high-resolution solid-state NMR techniques have been applied to hydrous silicate and aluminosilicate glasses simple acquisition, CPMAS, HETCOR, dipolar dephasing, spin counting, DQ correlation, and rotational echo double resonance (REDOR). ... 

Solid state NMR techniques, such as CP, RAMP CP, CP TOSS, MQ DEPT, 2D HETCOR, which are relevant to the characterisation of natural organic matter have been reviewed by Cook. The pros and cons of many of the techniques are compared in an effort to provide guidance to the most beneficial utilisation of the NMR techniques for researchers interested in natural organic matter. 

Recent developments of solid-state NMR techniques have allowed a direct and detailed analysis of the local structure of PAN in the solid state using homonuclear two-dimensional (2D) double quantum (DQ) (DOQSY) [187, 188] and H- C 2D heteronuclear multiple quantum (MQ) correlation (HMQC) [189] solid-state NMR spectroscopy. This method was applied to... 

D and multinuclear solid-state NMR were used to investigate a novel nanocrystalline pharmaceutical dispersion of ebselen with polyvinylpyrrolidone-vinyl acetate (PVP-VA), after initial characterization with other techniques. A nanocrystalline dispersion of ebselen with PVP-VA was prepared and characterized by ID and 2D solid-state NMR analysis involving H, C, and Se isotopes and H spin diffusion. 

The membrane-bound structure, lipid interaction, and dynamics of the arginine-rich p-hairpin antimicrobial peptide PG-1 has been studied by solid-state NMR. A variety of solid-state NMR techniques, including paramagnetic relaxation enhancement, and spin diffusion, dipolar recoupling distance experiments, and 2D anisotropic-isotropic correlation experiments, were used to elucidate the structural basis for the membrane disruptive activity of this representative p-hairpin antimicrobial peptide. 

Polarization Inversion Spin Exchange at the Magic Angle (PISEMA) high-resolu-tion solid-state NMR techniques can be used to investigate the influence of local chain dynamics on cooperative chain motions between the OCH3 protons of PMMA and the aromatic protons of PVPh [45,47]. The 2D experimental... 

The interactions between histidine and metal species play essential roles in a wide range of important biological processes including enzymes catalysis and signal transduction. Zhou et al. have employed solid-state NMR techniques to determine the interaction between histidine and Zn(ii) from pH 3.5 to 14. 2D homo- and heteronuclear correlation NMR experiments were utilized to extract the and N chemical... 

A novel crystalline form of the boron-containing antibacterial drug (5 )-3-(aminomethyl)-7-(3-hydroxypropoxy)benzo[c][l,2]oxaborol-l(3H)-ol hydrochloride has been studied by solid-state NMR and single-crystal X-ray diffraction techniques. After determination of the crystal structure by X-ray diffraction, solid-state NMR spectroscopy of this form is performed to obtain structural information using experimental approaches based on dipolar correlation, chemical shift analysis, and quadrupolar interaction analysis. solid-state NMR experiments at 16.4 T using MAS and homonuclear dipolar decoupling, 2D solid-state NMR experiments based on and dipolar heteronuclear correlation, and DFT... 

This chapter will be restricted to discussing solution NMR studies of polymers. For an excellent description of solid-state NMR techniques, the reader should first consult Chapter 2.07 of this comprehensive, by Saalwachter and Spiess. In the next section, some basic principles of NMR will be presented, followed by a discussion of ID-, 2D-, and 3D-NMR principles, techniques, and the information to be gained from each technique. The last seaion will be dedicated to examples of how these techniques can be used to leam about polymer struaures, including monomer composition, stereosequence effects, monomer sequence effects, short-chain branching, chain end structure, dendrimer stracture, and polymer branching, and other polymer defect structures. 

We then studied group 5 metals, especially tantalum-for which the laboratory already had great experience. Because of the studied reaction, alkyl or hydride-type compounds such as those developed in the laboratory could not be employed. Consequently, we became interested in alkoxo-type derivatives, either synthesized by reaction of the grafted complex with an alcohol or obtained by direct synthesis starting from an alkoxy-tantalum compound grafted on silica. In all cases, resulting complexes have been characterized by surface organometallic chemistry techniques, especially EXAFS and solid-state NMR (ID and 2D with C-labeled compounds). Indeed various compounds bonded by one, two or three surface bonds have been prepared and characterized. 

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