Echo Double Resonance NMR Spectroscopy Research Articles

Toward a biorelevant structure of protein kinase C bound modulators: design, synthesis, and evaluation of labeled bryostatin analogues for analysis with rotational echo double resonance NMR spectroscopy.

Protein kinase C (PKC) modulators are currently of great importance in preclinical and clinical studies directed at cancer, immunotherapy, HIV eradication, and Alzheimer's disease. However, the bound conformation of PKC modulators in a membrane environment is not known. Rotational echo double resonance (REDOR) NMR spectroscopy could uniquely address this challenge. However, REDOR NMR requires strategically labeled, high affinity ligands to determine interlabel distances from which the conformation of the bound ligand in the PKC-ligand complex could be identified. Here we report the first computer-guided design and syntheses of three bryostatin analogues strategically labeled for REDOR NMR analysis. Extensive computer analyses of energetically accessible analogue conformations suggested preferred labeling sites for the identification of the PKC-bound conformers. Significantly, three labeled analogues were synthesized, and, as required for REDOR analysis, all proved highly potent with PKC affinities (∼1 nM) on par with bryostatin. These potent and strategically labeled bryostatin analogues are new structural leads and provide the necessary starting point for projected efforts to determine the PKC-bound conformation of such analogues in a membrane environment, as needed to design new PKC modulators and understand PKC-ligand-membrane structure and dynamics.

Characterization of Reactive Sites in Supported Catalysts by 51V/15N Rotational Echo Double Resonance NMR Spectroscopy: Formation of Phenylimido Groups at Surface-Bound Oxovanadium Sites

Silica-supported oxovanadium groups were reacted in a gas-solid reaction with aniline at 175 degrees C. The reaction was clean as monitored in situ by UV-vis spectroscopy and resulted in the elimination of water as the principal product of the reaction and the disappearance of the terminal V=O stretch in the Raman spectrum. 15N MAS solid-state NMR spectroscopy showed only a single nitrogen-containing species on the surface. Proton-dephased 15N NMR showed only weak attenuation of its intensity, indicating that there are no protons directly bonded to the nitrogen. The formation of a vanadium-imido covalent bond was characterized by 51V/15N rotational echo double resonance NMR spectroscopy where the quadrupolar 51V nucleus was monitored and the spin-1/2 15N nucleus was dephased.

Determination of intermolecular distance for a model peptide of Bombyx mori silk fibroin, GAGAG, with rotational echo double resonance.

Rotational echo double resonance NMR spectroscopy is applied for the determination of the distance of intermolecular chains of pentapeptide, GAGAG (G: Gly, A: Ala), a model typical of the crystalline domain in Bombyx mori silk fibroin. 1:4 mixture of G[1-(13)C]AGAG and GAG[(15)N]AG with antiparallel beta-sheet structure was used to determine the distance of intermolecular hydrogen bonding between adjacent molecules within pleated sheet and the (13)C-(15)N interatomic distance was determined to be 4.3 A. On the other hand, 1:4 mixture of GAG[1-(13)C]AG and GAG[(15)N]AG gave information on the interpleated sheet arrangement. When we assumed the same distances between two interpleated sheets, the distance was calculated to be 5.3 A and the angle (15)N-(13)C-(15)N was 180 degrees.

Short and Medium Range Order in Sodium Aluminoborate Glasses. 2. Site Connectivities and Cation Distributions Studied by Rotational Echo Double Resonance NMR Spectroscopy

A quantitative NMR strategy is developed for the study of the network connectivity (intermediate range structure) and the cation distribution in the sodium aluminoborate glass system. The strategy is based on the analysis of rotational echo double resonance (REDOR) spectroscopy applied to the glasses and the crystalline model compounds Li6Al2(BO3)4, NaBO2, and Na2B4O7. The heterodipolar multispin interaction between the quadrupolar spin systems 27Al ↔ 11B and 23Na ↔ 11B is analyzed in terms of approximate second moments, which are extracted from REDOR data measured at short dipolar evolution times. On the basis of 27Al{11B} and 11B{27Al}-REDOR results, the framework connectivity distribution is extracted and compared to statistical and preferential bonding distribution scenarios, respectively. The sodium aluminoborate system is characterized by a large degree of bonding regularity in the framework. Four-coordinated aluminum is preferentially linked to BO3/2 and BO2/2O- units and vice versa, while linking ...