Heteronuclear decoupling
Optimization independent heteronuclear decoupling at fast MAS
Heteronuclear decoupling is important to maximize resolution and improve sensitivity. Several decoupling sequences such as TPPM, SWf-TPPM, SPINAL, XiX, AM-XiX and PISSARRO perform reasonably well but require careful experimental optimisation of at least one or more parameters. However, the optimised parameters are sensitive to experimental parameters. For samples with relatively high signal to noise, this is not an issue, and decoupling conditions can be re-optimised. However, samples with poor signal to noise are standard in solid-state and in such cases, optimisation of each parameter is demanding. Therefore, there was a need for heteronuclear sequences that are practically optimization independent, especially in the fast MAS regime where detection of 13C and 15N signals is very insensitive.
In the fast MAS regime (40 kHz and above), we have designed two low-power heteronuclear decoupling sequences that are practically optimization independent. The two new heteronuclear decoupling sequences are a) low-power rCWApAand b) the refocused-XiX (r-XiX). The knowledge of the MAS frequency and approximate RF fields is sufficient to predict the necessary parameters for decoupling.
![Untitled2](https://www.tifrh.res.in/~vipin/wp-content/uploads/2024/08/Untitled2.png)
Figure: decoupling performance of optimization independent sequences rCWApA and r-XiX with other sequence at 60kHz MAS and 10 kHz proton amplitude
Relevant Publications
- Asif Equbal, P.K.Madhu, Beat H. Meier, Niels C. Nielsen, Matthias Ernst and Vipin Agarwal Parameter independent low-power decoupling for Fast Magic-Angle Spinning in Solid-State NMR. J. Chem. Phys. (2017)
- Mukul G. Jain, K.N. Sreedevi, Asif Equbal, P.K. Madhu and Vipin Agarwal,Refocusing pulses: A strategy to improve efficiency of phase-modulated heteronuclear decoupling schemes in MAS solid-state NMR J. Magn. Reson., 284, 59-65 (2017)
- Kong Ooi Tan, Vipin Agarwal, Beat H. Meier and Matthias Ernst, A Generalized Theoretical Framework for the Description of Spin Decoupling in Solid-State MAS NMR: Properties of Low-Power Experiments. J. Chem. Phys., 145, 094201 (2016)
- Kshama Sharma, P.K.Madhu and Vipin Agarwal,Systematic evaluation of heteronuclear decoupling at rotary resonance conditions in the regime of fast MAS Magn. Reson., 270, 136-141 (2016)
- Vipin Agarwal, Tiit Tuherm, Andres Reinhold, Jaan Past, Ago Samoson, Matthias Ernst and Beat H. Meier. Amplitude modulated low-power decoupling sequences for Fast Magic-Angle Spinning NMR. Chem. Phys. Lett. 583, 1-7 (2013)