¹³C/¹⁵N distance determination by CPMAS NMR in uniformly ¹³C labeled molecules

Abstract

Abstract The REDOR and CPMAS techniques are applied for measuring 13 C 15 N dipolar coupling constants in glycine. It is shown that the selective CP or SPECIFIC CP technique removes the coherent evolution of the spin system under homonuclear 13 C 13 C J couplings. While the large coupling constant (∼900 Hz) is readily determined because of the presence of large oscillations in the CPMAS dynamics, their absence precludes the measurement of the small coupling constant (∼200 Hz). The experimental results and numerical simulations demonstrate that the determination of 13 C 15 N coupling constants of medium size (<1 kHz) by the CPMAS technique is mainly limited by the strength of the 1 H decoupling field and the size of the 13 C and 15 N chemical shift anisotropies. Copyright © 2005 John Wiley & Sons, Ltd.