Rotational-echo double-resonance REDOR NMR

Poly(benzyl ether) dendrimers synthesized by Frechet el al. have been studied with many techniques in order to reveal their conformational properties. Size exclusion measurements performed by Mourey et al. [154], rotational-echo double resonance (REDOR) NMR studies by Wooley et al. [155] and spin lattice relaxation measurements by Gorman et al. [156] reveal that back-folding takes place and the end-groups can be found throughout the molecule. The observed trends are in qualitative agreement with the model of Lescanec and Muthukumar [54],... 

One of the important applications of butylcalix[4]arenes arises from their ability to trap alkali metal ions. In particular, Cs+-calixarene complexes have received much attention because of the need to remove the Cs radionucleotide from nuclear wastes. Benevelli et al. have used one-pulse solid state NMR experiments to directly observe Li, Na and Cs ions in the host cavity [52]. More advanced experiments, which allow the investigation of metal lattice interactions were also reported. Rotational-echo double resonance (REDOR) NMR is a useful tool for obtaining structural details of butylcalix[4]arene [53]. Gullion and coworkers used REDOR to determine the position of the... 

From the success of the cross-polarization experiments, one may predict success for a variety of related experiments that depend on the dipolar interaction (such as those of Veeman [951, where spin echoes are observed under magic-angle spinning and double resonance conditions). Further experiments that allow determination of internuclear distances should also be possible, including rotational-echo double-resonance (REDOR) NMR [96], and transferred-echo double-resonance (TEDOR) NMR [97], the latter being related to INEPT experiments in liquids. 

H, and rotational-echo double-resonance (REDOR) NMR, applied to specifically labelled epoxy networks and the antiplastidser moiety, can provide information on the location of the antiplasticiser inside the epoxy network. Such an investigation has been performed in the case of HMDA/AP19 and HA60/AP19 networks [71] using [ N2] HMDA, [ N] HA, [ H labelled on the bis-phenol residue] DGEBA and [ C-carboxyl] EPPHAA. The main conclusions are ... 

Rotational-echo double-resonance (REDOR)(75,79) is a new solid-state NMR technique which is sensitive to through-space carbon-nitrogen interactions between selectively 13C and 15N-enriched sites separated by up to 5A (20-22). The parameter directly measured in a REDOR experiment is the heteronuclear dipolar coupling constant DCN, which is in itself proportional to the inverse third power of the intemuclear distance, rCN. It is this dependence on (icn)3 which accounts both for REDOR s ability to accurately measure short distances and its insensitivity to longer-range interactions. As a technique which can probe, in detail, intermolecular interactions over a distance range of 5A, REDOR is well suited to studying the distribution of small selectively-labeled molecules in polymer delivery systems. 

Rotational echo double resonance (REDOR) [86] is one of the most important techniques developed for solid-state NMR spectroscopy. The theory of REDOR is... 

Another study of the surface structure of CdSe NCs of 3.7 nm size used 31P MAS-NMR and 31P/77Se rotational-echo double-resonance (REDOR) to identify overlapping broad peaks from two surface species trioctylphosphine oxide (TOPO) at 29.3 ppm and trioctylphosphine selenide (TOPSe) at 22.2 ppm [343]. Both the isotropic chemical shift and CSA of the surface-bound TOPO were substantially different from those of the free ligand. Spin-echo experiments on 31P were stated to indicate an average P-P distance of 8-10 A at the surface, consistent with capping at alternate atomic sites (all Cd but not Se). 

The synthesis of a range of silicon boron carbonitride ceramics can conveniently be carried out by thermal treatment of suitable amorphous precursor molecules in which the desired atomic linkages are already in place. A series of new amorphous precursor molecules has been investigated by "B MAS NMR and double resonance techniques such as Si- B) Rotational Echo Adiabatic Passage DOuble Resonance (REAP-DOR) and B-j Si) Rotational Echo DOuble Resonance (REDOR) (van Wiillen and Jansen 2001). The results indicate the presence of hexagonal BN and (3-Si3N4 in some... 

Fluorine-probe protocol has been applied to solid-state magic-angle spinning (SSMAS) 19F NMR analysis with the radiofrequency-driven dipolar recoupling (RFDR) method to measure the F-F distance in the microtubule-bound conformation of F2-10-Ac-docetaxel (see Figure 1.29a) [167], Moreover, five intramolecular distances of the key atoms in the microtubule-bound l9I72II/l3(Mabeled paclitaxel were determined by the rotational echo double resonance (REDOR) method (see Figure 1.29b and c) [168, 169],... 

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). ... 

A rotational-echo, double-resonance (REDOR) 15N-I3C NMR experiment has been performed on an alanine co-crystallized from five-component alanines, isotopically enriched in l3C, 15N, or I3C.41-43 REDOR 15N-I3C NMR involves the dephasing of carbon magnetization by 15N 180° pulses synchronized with magic-angle spinning. The C-N dipolar coupling deter-... 

As with the 2DTOSS studies, Munson and co-workers showed that solid-state NMR can provide important information on the structures of polymorphs and solvates whose crystal structure is not known. As we seek more detailed structural information of drugs in order to understand more about solid-state behavior, these 2D techniques will no doubt become more and more important. Additional 2D techniques have been utilized to study DNA complexes (104) and perform distance measurements (105), specifically using the rotational-echo double-resonance (REDOR) sequence (106,107). 

The most powerful tool to study the intermediate range order in amorphous Si/B/N/(C) networks is MAS-NMR spectroscopy including advanced double resonance techniques such as B- Si rotational echo double resonance (REDOR), Si- B] rotational echo adiabatic passage double resonance (REAPDOR), and C- B] REAPDOR. These methods utilize the heteronu-clear coupling between the observed nucleus and a nucleus in the second coordination sphere to get information about the internuclear distance of the two nuclei. 

In 1989 Gullion and Schaefa described the rotational-echo, double-resonance (REDOR) technique. Distances measured by this method may be used in the detemination of bound-ligand conformations without the limitations imposed by crystallization, molecular weight or solubility. They have performed REDOR NMR... 

Having demonstrated the achievement of high-resolution sohd state NMR capability, the authors describe experiments that combine the high-resolution aspect of MAS NMR with methods that retain the structure and/or dynamic information inherent in the anisotropic interactions. Rotational-echo double resonance (REDOR) allows the determination of D between isolated heteronuclear spin pairs. D is related simply and without approximation to intemuclear separation. Hence, REDOR makes possible the unambiguous direct determination of intemuclear distance between the labeled spin pair, independent of pair orientation, i. e., in amorphous and /or microaystaUine solids, and extends our abihty to quantitatively explore complex materials. It is also possible to extract intemuclear distance from homonuclear dipolar coupled spin pairs, and these experiments are also reviewed. 

A series of ID and 2D NMR experiments performed on nanocomposites of hectorite, a smectite clay mineral, showed new opportunities for studying large assemblies of layered minerals with polymeric materials.In particular. rotational-echo double-resonance (REDOR) experiments afforded H- Si distances with precision, and a mobility gradient of intercalated polyethyleneoxide (PEG) segments was demonstrated in H-" Si wideline separation (WISE) experiments. 

The silk I structure (the structure of Bombyx mori silk filroin before spiimiiig in the solid state) was detenxiined with two-dimensional (2D) spin-dffiision solid-state NMR, rotational echo double resonance (REDOR) and quantitative use of CP/MAS NMR chemical shifis. We used double labeled and double labeled model... 

Progress has been made recently in identifying bonds between catecholamine aromatic and aliphatic carbon to protein nitrogen in insect cuticle by solid-state H- C- % double-cross polarization (DCPMAS) NMR. (65) and rotational-echo, double resonance (REDOR) C and N NMR (M,67, Christensen et.al., unpublished data). Tobacco hornworm pupal exuviae were labeled by injec-combination of [ring- N2)histidine and either (ring-... 

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