SPEEDY:  Spin−Echo Enhanced Diffusion Filtered Spectroscopy. A New Tool for High Resolution MAS NMR

Abstract

The pulsed field gradient diffusion edited experiment, bipolar LED, has been combined with the Carr-Purcell-Meiboom-Gill (CPMG) spin-echo sequence for the analysis of solid phase resin samples. Spin-echo enhanced diffusion filtered spectroscopy (SPEEDY), when optimized, filters both the compounds that demonstrate fast diffusion rates as well as the compounds that demonstrate fast T(2) relaxation rates. Using this technique, compounds that are not covalently attached to the resin are not observed and contributions from the resin matrix are greatly attenuated. The interpretation of the resulting spectrum is more readily accessible. This technique lessens the importance of completely removing reaction residues or the wash solvents simply for analytical evaluation. The utility of the combined filtering scheme was demonstrated by the implementation into a NOESY sequence.

HR-MAS NMR Spectroscopy in Material Science

“…This work includes the development of diffusion filtered HR-MAS NMR techniques to study the gelation process of super-molecular gels, [95] along with a combination diffusion-filtering and a spin-echo enhanced (T2 -filtered) experiment on DMFswollen resins. [96] These techniques allowed the identification of free and surface bound molecules, while eliminating the signal from the immobile bulk resin matrix. In complex mixtures there may be future avenues for HR-MAS to resolve subtle differences in the local chemical environments as demonstrated in the following example.…”

Analysis of Protein/Ligand Interactions with NMR Diffusion Measurements: The Importance of Eliminating the Protein Background

“…However, for specific binding interactions the use of relatively large ligand concentrations places one outside the optimum concentration regime for detecting changes in the ligand diffusion coefficient. Relaxation editing can also be used to reduce the background due to the protein magnetization by incorporating a spin echo or CPMG pulse train into the diffusion pulse sequence (29,30). However, this method may also greatly reduce the intensity of the ligand resonances, which are broadened as a result of protein binding.…”

Improved Spin-Echo-Edited NMR Diffusion Measurements

“…of the longitudinal eddy current delay diffusion pulse sequence was recently reported for the NOESY analysis of molecules bound to solid-phase synthesis resins (25). The spectrum obtained using a 62-ms CPMG pulse train in the CPMG-BPPSTE pulse sequence is shown in Fig.…”