z-Filtered double-quantum NMR spectra and automated analysis by pattern recognition

The refocused INADEQUATE MAS NMR experiment in multiple spin-systems: Interpreting observed correlation peaks and optimising lineshapes

“…Specifically, and as suggested in particular in Refs. [43] and [44] for liquid-state NMR INADEQUATE and refocused INADEQUATE experiments, four-step phase-cycling of the final 90°pulse (consisting of / = 0, 90, 180, 270°and / receiver = 0, 90, 180, 270°) is required to remove contributions of coherence order ±2, and thus eliminates half the intensity of the undesired contributions listed in Table 1, which, as described in Eqs. (10) and (11), are converted to a mixture of DQ and ZQ coherences by the first 90°pulse of the z-filter.…”

Product operators, coherence pathways, and phase cycling part i: product operators, spin‐spin coupling, and coherence pathways

“…One way to simplify the expressions is to use complex linear combinations of the operators I, and I,, such as the shift operators, I + = I, + iZ, and I -= I, -iZ, (9,18,19), or the spherical basis set, I + , = -Z+J.\/Z and I -, = Z-l.\/Z (7,10). A similar effect occurs during spin-spin coupling (9, 10).…”

“…Coupled spin systems in more complicated pulse sequences can be described accurately by the density matrix formalism (3-7). This cumbersome approach is often replaced by the more convenient product operator formalisms ( I , [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The various product operator methods differ in the basis set chosen to represent the density matrix, and each basis set has advantages and disadvantages.…”

“…Although this can be considered to represent a single rotated vector, if each vector or operator is followed separately, the expressions expand into 4, 8, etc., terms. One way to simplify the expressions is to use complex linear combinations of the operators I, and I,, such as the shift operators, I + = I, + iZ, and I -= I, -iZ, (9,18,19), or the spherical basis set, I + , = -Z+J.\/Z and I -, = Z-l.\/Z (7,10). (The spherical basis set also uses the p notation I, instead of I,.)…”

A computer-based protocol for semiautomated assignments and 3D structure determination of proteins

“…One way to reduce the time required for NMR-based structure determinations is to implement computer algorithms that perform the mundane and monotonous chores of spectral analysis. Among the aspects of N M R spectral analysis that have been subjected to computer automation are peak-picking (Pf~indler et al, t985;Glaser and Kalbitzer, 1987;Hoch et al, 1987;Stoven et al, 1989;Garret et al, 1991) and the identification of spin systems by amino acid types (Neidig et al, 1984;Pf'~indler et al, 1985;Novic et al, 1987;Grahn et al, 1988;Weber et al, 1989;Eccles et al, 1991). Once spins systems have been correctly identified, computer strategies have been developed that make use of extensive bookkeeping and consistency checking (Billeter et al, 1988) to obtain the sequential assignments.…”