Fast multidimensional NMR spectroscopy by spin-state selective off-resonance decoupling (SITAR)

Abstract

Spin-state selective off-resonance decoupling (SITAR) is applied to the amide proton-to-nitrogen-to-alpha-carbon correlation (HNCA) triple-resonance experiment by measuring the 15N chemical shift during the acquisition simultaneously with the 1H chemical shift. The simultaneous detection of both 1H and 15N chemical shifts in SITAR reduces the dimensionality of the HNCA-type experiment from three dimensions to two dimensions with a 15N chemical shift resolution of approximately 0.4 ppm. This enables the recording of triple-resonance experiments in several minutes. SITAR is furthermore applied to the amide proton-to-nitrogen-to-alpha-carbon-and-beta-carbon correlation (HNCACB) triple-resonance experiment and the 15N-resolved [1H,1H]-nuclear Overhauser enhancement spectroscopy (NOESY) experiment with similar success. The accompanied peak crowding and chemical shift degeneracy of the amide protons in the SITAR two-dimensional (2D) spectra, which are inherent properties of pseudo-dimensional experiments, are resolved by local correlation of the two sub-spectra. With this procedure a 13C--1H strip for each 15N--1H moiety is generated resulting in a three-dimensional (3D) strip list known from the conventional 3D spectra. The quality of the strip list in terms of peak crowding and chemical shift degeneracy is comparable to their corresponding 3D counterparts. An analysis-software within the CARA package is presented, which generates, visualizes and manages the SITAR spectra, the corresponding strip lists and the assignment process.

Segmental isotopic labeling of the Hsp70 molecular chaperone DnaK using expressed protein ligation

“…All NMR experiments were performed using standard pulse sequences from Bruker TopSpin 1.3 software. Data were processed using NMRPIPE40 and analyzed using CARA 41…”

Tailored real-time scaling of heteronuclear couplings

“…The idea of using off-resonance decoupling to obtain chemical shift correlations in 1D-spectra was proposed by Ernst [17] and has then been used for the acquisition of pseudo-multidimensional spectra [20][21][22][23]. However, so far this concept was limited to using cw decoupling for scaling J-couplings.…”

“…For example, band-selective decoupling sequences are designed to have a scaling factor of zero in a defined offset range and a scaling factor of one in other offset ranges [12][13][14][15][16]. Another example is the well defined offset-dependent scaling factor of continuous wave (cw) irradiation [4,17], which has been extensively used for chemical shift monitoring in pseudo-multidimensional experiments [18][19][20][21][22][23]. In favorable cases, this robust, efficient and fast method allows to reduce the number of dimensions in multidimensional NMR experiments by one, saving acquisition time by avoiding time-consuming coherence transfer and indirect evolution steps [21][22][23][24].…”

“…Another example is the well defined offset-dependent scaling factor of continuous wave (cw) irradiation [4,17], which has been extensively used for chemical shift monitoring in pseudo-multidimensional experiments [18][19][20][21][22][23]. In favorable cases, this robust, efficient and fast method allows to reduce the number of dimensions in multidimensional NMR experiments by one, saving acquisition time by avoiding time-consuming coherence transfer and indirect evolution steps [21][22][23][24]. Related experimental approaches to reduce the dimensionality of NMR experiments based on the scaling of coupling evolution include SPEED (single-point evaluation of the evolution dimension) [25] and coupling evolution during adiabatic pulses [26].…”

Multi-dimensional NMR without coherence transfer: Minimizing losses in large systems

“…The idea of encoding indirect chemical shifts through decoupling during acquisition also shares some similarity with the SITAR (spin-state selective off-resonance decoupling) method from the Riek laboratory [14,15]. However, DIRECT methods and the SITAR methods are fundamentally different.…”