title: QUantitative Cross-Polarization at magic-angle spinning frequency of about 20 kHz.
abstract: We study the QUantitative Cross-Polarization (QU-CP) method proposed by Hou et al. (Chem. Phys. Lett. 421 (2006) 356) under the moderate MAS speed of 23 kHz, re-examining its two building blocks, namely, the CP polarization transfer from (1)H to (13)C, and the thermal equalization of the (13)C magnetizations. We show that the nuclear-integrated cross-polarization (NI-CP) scheme is conveniently used for (1)H-(13)C polarization transfer, because of its simplicity, robustness to rf-mismatch, and compatibility with fast sample spinning. In the mixing part, in addition to dipolar-assisted rotational-resonance (DARR) recoupling, we examine the Phase-Alternated Recoupling Irradiation Schemes (PARIS and PARIS(xy)), and Second-order Hamiltonian among Analogous Nuclei Generated by Hetero-nuclear Assistance Irradiation (SHANGHAI) sequences, and show that SHANGHAI gives the best performances in equalizing the (13)C magnetizations.
authors.affiliation: Division of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan. takezo@kuchem.kyoto-u.ac.jp
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Takeda
authors.forename: Yasuto
authors.initials: Y
authors.lastname: Noda
authors.forename: K
authors.initials: K
authors.lastname: Takegoshi
authors.forename: Olivier
authors.initials: O
authors.lastname: Lafon
authors.forename: Julien
authors.initials: J
authors.lastname: Trébosc
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Amoureux
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D013113:Spin Labels
chemical_list: D013113:Spin Labels