Binuclear spin state selective detection of 1H single quantum transitions using triple quantum coherence: A novel method for enantiomeric discrimination

Multinuclear NMR in polypeptide liquid crystals: Three fertile decades of methodological developments and analytical challenges

“…Series c: Δσ aniso ≠ 0 with T S > Δσ aniso with T R > Δσ aniso Series d: Δσ aniso ≠ 0 with T S < Δσ aniso and T R < Δσ aniso Series e: Δσ aniso ≠ 0 with T S > Δσ aniso and T R < Δσ aniso T S > 2Δσ aniso T S = 2Δσ aniso T S < 2Δσ aniso T S = 0 T S > 2Δσ aniso + T R T S = 2Δσ aniso + T R T S < 2Δσ aniso + T R T S = T R T S ≠ T R T S = T R < Δσ aniso T S = T R = Δσ aniso T S > 2Δσ aniso + T R 2ΔΔσ -T R < T S < 2Δσ aniso + T R T S > 2Δσ aniso -T R T S = 2Δσ aniso +T R T S = 2Δσ aniso -T R large magnitude of anisotropic interactions, such as ( 1 H-1 H)-RDCs, leads to second-order 1 H-NMR spectra. As a consequence, during two decades, numerous practical approaches were developed to simplify the analysis of strongly oriented 1 H NMR spectra, and subsequently also of 13 C. Without being exhaustive, we can mention: i) the selective or partial deuteration [65,66]; ii) the use of multiple quantum (MQ) 2D experiments [67,68,69,70] or the combination of them [71]; iii) the reduction of anisotropic interactions by spin manipulation via appropriate multiple-pulse sequences [72,73,74,75]; or iv) the variable angle spinning sample (VASS) technique [76,77,78,79].…”

Applications of spin‐spin couplings

“…In another experiment natural abundant 13 C as a passive spin for the state selective 3Q-SQ correlation has been used. 18 Using the latter method it is possible to determine both homo-and heteronuclear couplings in a single experiment, and the measured parameters are precise due to upward scaling of the couplings. The same group of the authors 19 using the combination of homo-and heteronuclear multiple quantum experiments have measured the magnitudes and signs of the scalar and dipolar couplings of different isotopomers of doubly labelled acetonitrile ordered in liquid crystal.…”

Spin-Selective Correlation Experiment for Measurement of Long-Range J Couplings and for Assignment of (R/S) Enantiomers from the Residual Dipolar Couplings and DFT

“…10 The naturally abundant 13 C edited selectively excited multiple quantum techniques for extraction of homo-and heteronuclear couplings have also been reported. 11 Residual dipolar couplings (RDCs) are considered as global parameters in studying structures and conformations of proteins and conformational analysis of oligosaccharides. 13,14 The diverse aligning media with a low-order parameter for molecules soluble in polar or nonpolar medium and several weakly orienting chiral solvents for discrimination of enantiomers have been reported.…”

“…In spite of the first-order splitting pattern in these media, the 1 H spectra are undecipherable even for a very small molecule containing 5À6 coupled protons. 11 Therefore, extraction of both long-range homo-and heteronuclear RDCs is a challenging task.…”

“…A myriad of NMR experiments viz, HSQC-TOCSY, 2D hetero-half-filtered TOCSY (HETLOC), phase-sensitive HMBC (PS-HMBC), long-range-optimized HSQC, etc., have been reported for such a purpose. − Recently, the IPAP-HSQMBC experiment for determination of long-range J couplings from the spin-state-selective multiplets has been demonstrated . The naturally abundant 13 C edited selectively excited multiple quantum techniques for extraction of homo- and heteronuclear couplings have also been reported …”