Cross polarization in the tilted frame: assignment and spectral simplification in heteronuclear spin systems

Abstract

A frequency selective heteronuclear polarization transfer technique is introduced for rotating solids. In this method, radiofrequency fields comparable with the frequency offsets are applied to establish Hartmann-Hahn cross polarization that therefore depends explicitly on the resonance offset of the nuclei involved. Under these conditions, spectrally induced filtering in combination with cross polarization (SPECIFIC CP) can be achieved and is demonstrated to be useful for spectral simplification or assignment in heteronuclear spin pairs. The design principles are outlined and demonstrated experimentally on I3C, "N labelled amino acids.

Application of REDOR subtraction for filtered MAS observation of labeled backbone carbons of membrane-bound fusion peptides

“…Reported TEDOR efficiencies are between 0.05 and 0.35 [46][47][48][49][50][51]. Finally, filtering with 15 N-13 C cross-polarization between directly bonded pairs has been used for amino acids, peptides, and proteins and the reported efficiencies are between 0.40 and 0.70 [50][51][52][53][54][55][56]. When 15 N-13 C cross-polarization was applied to observe all directly bonded pairs in a crystalline U-13 C, 15 N-labeled tripeptide, E $ 0:40, which is similar to what we obtained with REDOR for HFP-KKK-UF8L9G10 [51].…”

Proton-detected scalar coupling based assignment strategies in MAS solid-state NMR spectroscopy applied to perdeuterated proteins

“…NMR experiments were carried out under MAS (14 and 24 kHz, as indicated in the respective figures) using Bruker Avance spectrometers operating at 1 H Larmor frequencies of 400, 600, and 700 MHz. In all experiments, 15 N chemical shift is evolved in a constant-time manner during the reverse INEPT step in which the 15 N, 13 C scalar coupling is refocused. Pulse programs were adapted from Bruker standard programs employing the sequences suggested by Kay, Bax, Müller and co-workers for HNCO [34,35], HNCA [34,35], and HNCACB [36] (Fig.…”

“…Modifications of the pulse schemes involve simplified solvent suppression due to the little amount of residual water in the micro-crystals. Soft rectangular instead of shaped pulses were used in the case of on-resonance 13 C selective irradiation in order to cut down the length of the overall sequence. Scalar heteronuclear decoupling during acquisition was applied using a RF field strength in the order of 2 kHz.…”

“…Usually, assignment of proteins in the solid-state is based on correlations among heteronuclei like 13 C or 15 N, employing NCACX or NCOCX type experiments [13][14][15]. This strategy relies on well dispersed resonances in the 15 N dimension.…”

GAVA: Spectral simulation for in vivo MRS applications

“…Despite the increase in available tools, GAMMA has maintained a strong presence in the field due to its flexibility, performance, straightforward elegant design and standard C++ implementation. There have been numerous reports of spectral simulations that have made use of the GAMMA library [3,[8][9][10][11][12][13][14]19,21,22,25,26,30,34,[37][38][39]41,50,51]. However, use of the GAMMA library also requires familiarity with C++ programming and it provides only rudimentary tools for the display, storage and analysis of results.…”