J-modulated ADEQUATE experiments using different kinds of refocusing pulses |
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Authors: | Thiele Christina M Bermel Wolfgang |
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Affiliation: | 1. Clemens Sch?pf Institut für Organische Chemie und Biochemie, TU Darmstadt, Petersenstr. 22, 64287 Darmstadt, GermanyClemens Sch?pf Institut für Organische Chemie und Biochemie, TU Darmstadt, Petersenstr. 22, D‐64287 Darmstadt, Germany.===;2. Bruker Biospin GmbH, Silberstreifen, 76287 Rheinstetten, Germany |
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Abstract: | Owing to the recent developments concerning residual dipolar couplings (RDCs), the interest in methods for the accurate determination of coupling constants is renascenting. We intended to use the J-modulated ADEQUATE experiment by K?vér et al. for the measurement of (13)C - (13)C coupling constants at natural abundance. The use of adiabatic composite chirp pulses instead of the conventional 180 degrees pulses, which compensate for the offset dependence of (13)C 180 degrees pulses, led to irregularities of the line shapes in the indirect dimension causing deviations of the extracted coupling constants. This behaviour was attributed to coupling evolution, during the time of the adiabatic pulse (2 ms), in the J-modulation spin echo. The replacement of this pulse by different kinds of refocusing pulses indicated that a pair of BIPs (broadband inversion pulses), which behave only partially adiabatic, leads to correct line shapes and coupling constants conserving the good sensitivity obtained with adiabatic pulses. |
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Keywords: | NMR 13C?13C coupling constants ADEQUATE BIP |
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