No Relaxation Delay (NORD) NMR spectroscopy is a method for making the acquisition of NMR spectra less time consuming. By modification of the pulse sequences and careful ordering of the experiments it is possible to eliminate the most time consuming part, the relaxation delay.
The idea behind NORD experiments is to arrange a series of experiments so that unused magnetisation relaxes during one pulse sequence, leaving it available for the next sequence. This allows the relaxation delay to be eliminated completely and the total experimental time to be reduced.
The NORD sequences published to date incorporate less commonly used experiments. As well as a standard HMBC module, SEA XLOC and 2BOB/H2OBC modules have been used. The SEA XLOC experiment provides long range correlations with differentiation of two and three bond correlations. The 2BOB/H2OBC experiment produces a H2BC spectrum and a HSQC-like one bond correlation spectrum.
Processing NORD data requires separating the interleaved data into separate files before applying standard processing steps. Data separation can be easily done in TopSpin. NORD experiments are compatible with NUS.
The most recent NORD paper shows good quality spectra collected in a few minutes on a concentrated sample (45 mg of a trisaccharide), however, I have not tested them myself yet. To assess how well they work it would be best to compare the NORD spectra against those collected individually. To do this the unusual NORD modules will have to be implemented as well.
The NORD experiment is an extrapolation of the NOAH concept, and likely has the same advantages and drawbacks. Tailoring acquisition parameters for the individual spectra is likely difficult, if not currently impossible, but for routine data acquisition the NORD experiments may be useful.
References
NORD: NO Relaxation Delay NMR Spectroscopy
TM Nagy, KE Kövér, OW Sørensen
Angewandte Chemie International Edition 2021, 60, 13587-13590
Double and adiabatic BANGO for concatenating two NMR experiments relying on the same pool of magnetization
TM Nagy, KE Kövér, OW Sørensen
Journal of Magnetic Resonance 2020 316, 106767
BANGO SEA XLOC/HMBC–H2OBC: complete heteronuclear correlation within minutes from one NMR pulse sequence
TM Nagy, T Gyöngyösi, KE Kövér, OW Sørensen
Chemical Communications 2019 55(81), 12208-12211
Distinguishing between two-and three-bond correlations for all 13C multiplicities in heteronuclear NMR spectroscopy
T Gyöngyösi, TM Nagy, KE Kövér, OW Sørensen
Chemical Communications 2018 54(70), 9781-9784
I wonder what the last sentence means and what exactly is considered impossible or difficult.
ReplyDeleteBrendan: In a NORD concatenation of experiments you can always tailor the acquisition parameters of the least sensitive module exactly as you like. In the other modules, you can either keep the same number of scans per t1 increment as for the least sensitive module or you can opt for less scans per t1 increment and a higher resolution in t1. You are welcome to contact me with any questions you might have regarding NORD. Ole
ReplyDeleteOle: My apologies for the slow response. I did not receive notification of your comments and only found them today when looking for something else.
DeleteThe comment about being difficult or impossible to tailor different modules was based on my impression that since each module is acquired in the process of one scan then all must be acquired with the same number of scans and increments. If this is incorrect then it offers a definite advantage over NOAH experiments.
Brendan: Another way of putting the flexibility is that you acquire the same total number of FIDs for all concatenated modules. This number is the product of the number of increments (NI) and the number of scans (NS) for each increment. You choose NI and NS for each module independently only requiring that the product of the two is the same for all modules. This flexibility you also have with the NOAH approach. For the meaningful experiments the advantage of NORD is higher sensitivity due to running them without the need for a relaxation delay.
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