Details

Autor(en) / Beteiligte

• Ogaeri, Yutaro
• Suzuki, Naoto
• Fukami, Toshiro
• Nishiyama, Yusuke

Titel

Internuclear distance measurements between 1 H and 14 N in multi-component rigid solids at fast MAS

Ist Teil von

• Journal of magnetic resonance (1997), 2023-03, Vol.348, p.107378

Ort / Verlag

United States

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• H- N internuclear distances are readily and accurately measured using the symmetry-based phase-modulated resonance-echo saturation-pulse double-resonance (PM-S-RESPDOR) method in rigid solids. The fraction curve, (S - S')/S , is represented by a single variable of a H- N heteronuclear dipolar coupling, where S and S' are the PM-S-RESPDOR signal intensity with and without N PM saturation pulse, respectively. Analytical equation of the fraction curve easily provides H- N couplings. This treatment is only applicable when NH proton resonance is well separated from the other proton peaks. With the limited H resolution even at fast MAS > 60 kHz, unfortunately, this condition is not necessarily satisfied especially in multi-component systems which often appear in pharmaceutical applications. To overcome this problem, T-HMQC filtering is applied to suppress the H signals other than NH proton prior to the PM-S-RESPDOR experiments. The method is well demonstrated on two components acetaminophen-oxalic acid (APAP-OXA) systems. Further analysis of orientation dependence of T-HMQC and PM-S-RESPDOR shows that the analytical equation can be safely applied in the analysis of T-HMQC filtered PM-S-RESPDOR experiments.