On-demand webinar: NMR supersequences and multiple receivers in small molecule analysis

Watch this on-demand webinar, where Dr. Eriks Kupce, principal scientist at Bruker UK, introduces the concept of constructing NMR supersequences from modules that are simple modifications of conventional NMR sequences. The proposed method is based on the 'domino principle' - the output of the previous module must match the input of the following module.

In this on-demand webinar, Dr. Kupce will demonstrate that significant gains in both speed and sensitivity can be achieved in well-designed NOAH (NMR by ordered acquisition using 1H detection) supersequences. Furthermore, such supersequences can be constructed with a particular application in mind, for instance, establishing the structure of small molecules from a single measurement. Combining NOAH with the use of multiple receivers and multi-nuclear detection offers further enhancements.

Read on for the highlights of the live Q&A session or register to watch the webinar at any time that suits you.

Q: Does the sequence work for a mixture analysis and is it workable on any NMR probe, BBI, BBO, HR-MAS, or does it need to have specialized settings?

EK: To answer the first part of the question is, yes, it can be used for mixtures. We have done some limited work in this direction and like in the other pulse sequence, it can be used for a mixture. There is no particular reason why it shouldn’t. The answer to the second part of the question is, yes. We have implemented the sequences even on benchtop systems. They should work with any type of probes, even on probes that don't have gradients. They have very robust experiments

Q: Would it be possible to combine it with ESGP water suppression or similar to get a TOCSY and NOESY of peptides in water?

EK: Yes, we have done limited work in water with presat. This is the direction where we will do more work and water suppression is possible. You might need to do some more water suppression in the pulse sequence itself, like WATERGATE or similar. In principle, it's possible, but we've been mostly focusing on different types of NOAH supersequences, not so much on details, which obviously also need to be addressed, at some point.

Q: Is it right to assume that any reference shift will be the same for all 2D spectra acquired with NOAH combination, and how do you deal with the differential intensity since there are many times intrinsic for each experimental unit? Is there a way to set an expected S/N ratio of a user-defined region to define a number of scans, for example?

EK: In general, reference shifts, yes, they will be the same, as long as these shifts happen slowly or they are longer than, single incrementing or not modules. We did use this, to correct instabilities in the PANACEA spectra where we use C-13 1D spectra to correct for instabilities and that worked very nicely. I suppose the same can be done also in the NOAH experiments.

Regarding the intensities, that is probably a bit more complicated, because there are different types of NOAH experiments in some of them. Magnetization is kept along z-axis. In some of them, there is a relaxing in x-y plane or along z-axis. Then, the intensities will be affected by relaxation effects. I would say its hard to design NOAH experiments for quantitative NMR. I haven't really looked at S/N ratios, so that probably needs some further attention.

Q: What is the minimum sample amount that is needed for such experiments? Is 10 milligrams of a small molecule, about 500 Daltons, enough to get a presat of HMBC, HSQC, COSY, ROESY, in 1 hour?

EK: Yes, if you can do this with the standard experiment, then you should be able to do this with the NOAH sequences. For the number of increments that you need, is slightly depending on what type of experiments you run. It may not be easy to set the level of randomization in NOAH experiments for each individual module.

Q: What's the maximum molecular size or weight that can be studied by NOAH experiments? Do bigger molecule sizes mean faster relaxation, but then that might also favor the signal intensity recovery?

EK: If the experiment works for your given size of the molecule, then you can use up the module in the NOAH sequences. NOAH experiments are based on ASAP pulse sequences, which are kind of similar so SOFAST sequences and BEST sequences in biomarker NMR. It looks to me that as long as the experiment itself runs, you can go all the way to the size of biomolecules.

Q: Are there NOAH supersequences available for samples in water?

EK: Yes, there are some NOAH sequences that basically use a presat. If they don't have presats, you can always add presats. In general, a presat is more or less the water suppression techniques that is kind of easier to use with mass. On the other hand, if experiments are based on coherence, gradients, they will suppress water natural. In principle, you can use water suppression. Perhaps there is more space for development.

Q: How does the S/N and acquisition time compare with that of the experiments acquired individually?

EK: You can use any number of increments and data sizes you want. Perhaps you don't want to use too long acquisition, for two reasons. One reason is, typically in CryoProbes, decoupling power limits how long you can acquire the experiments. Secondly, if the acquisition time becomes comparable with a relaxation period, then the speed at which you can run these experiments is also lower. It is still advantageous to do it that way in mass, but the advantages are going be smaller.

Q: Can you apply the NOAH methods to proteins and/or polypeptides as well?

EK: We have applied it to peptides like cyclosporin and gramicidin. They can definitely be used for studying polypeptides. The T2 affects that means the acquisition times for larger molecules will get shorter and may even be advantageous for NOAH supersequences. I think there is no reason why these experiments cannot be applied to peptides and polypeptides.

Watch this webinar to learn more about NMR by ordered acquisition using 1H detection (NOAH) methods>>