Aditi Pandey (Centre of BioMedical Research, India)
Abstract: Accurate metabolite assignment is essential for effective metabolomics research. 2D NMR spectroscopy such as 1H-13C HSQC and 1H-1H TOCSY plays vital role in the identification of metabolites when combined with spectral databases. However, collecting high quality HSQC data from biofluids at natural 13C abundance requires large number of scans and hence NMR time typically of the order of 12-24 hours even at high fields (600-800MHz) with cryogenic probes. Performing further COSY and TOCSY in high resolution mode can result in additional hours. While NOAH (NMR by Ordered Acquisition using 1 H detection) supersequences offer
time-efficient acquisition by combining multiple experiments in a single pulse sequence using a single recovery delay without sacrificing sensitivity. This is achieved by reusing unused magnetization from one experiment (e.g. HSQC) for subsequent ones (e.g. TOCSY). However due to high complexity of biofluids standard TOCSY spectra often suffers from peak overlap.
The PSYCHE-TOCSY experiment helps resolve this by generating one sharp peak per resonance, thus minimizing overlap. Thus we want to introduce a novel HSQC+PSYCHE-TOCSY NOAH2 supersequence that combines HSQC with PSYCHE-TOCSY to provide fasterand clearer analysis of complex metabolite mixtures in biofluids.
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Hello! Very nice work congratulations!
I was wondering, in your NOAH-based sequence, how much sensitivity is lost (if any) compared to the two experiments acquired separately? How much time is then saved?
Thank you very much!-
Hello Marco, very insightful query indeed!
Actually when we record a PSYCHE-TOCSY separately at all the same acquisition parameters, there is negligible loss in the sensitivity. Here we have compared it with a regular TOCSY, which is although more sensitive but we are often not able to make full use of it due to the crowded peaks.
I hope you understand. You can further ask any more queries.
Thank you!
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That’s quite impressive!
How does the resolution of the NOAH sequence compares to the a PSYCHE-TOCSY, as opposed to a regular TOCSY?
The NOAH TOCSY (pannel D in the 1D and 2D NMR Spectra assignment pannel) seems to show some artifacts at 5ppm in F1. Can you comment on that? Also water suppression seems a lot better, what is the reason?
How does the signal-to-noise ratio compare between the experiments?Thanks!
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Hello Nicolas, thanks for your kind appreciation.
The resolution in PSYCHE-TOCSY from NOAH sequence is same as standalone PSYCHE-TOCSY. The artefact is due to some phase problem.
For water suppression we have used presaturation block before the start of TOCSY sequence and excitation sculpting, placed just before the acquisition in homonuclear module.
The SNR of the two experiments is very similar.
I hope this resolves your query. Thank you!
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