Ribal Jabbour (New York University Abu Dhabi, UAE)
Abstract: Dynamic Nuclear Polarization (DNP) is a technique that utilizes the sensing capability of electron spins to significantly enhance the sensitivity of NMR signals, particularly for low-sensitivity samples. Glassing agents are essential in the DNP process, as they facilitate the transfer of polarization from unpaired electron spins to nuclear spins while providing cryoprotection. Glycerol/D2O/H2O mixtures have been widely used as glassing agents for this purpose over the past two decades. However, glycerol exhibits two prominent peaks in NMR spectra, which can obscure signals in certain regions. Using alternative glassing agents can mitigate this issue, uncovering these regions for clearer analysis. Additionally, DNP without any glycerol can be employed to study off-the-shelf insulin, which can enable detailed structural of this critical biomolecule.
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Hi Ribal, Thank you for your presentation.
Did you estimate the proton concentration in your final sample and how does it compare with a more traditional DNP juice formulation, and did you try different concentrations of radical to optimize the enhancement?
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Hi Chloé,
We did not estimate the proton concentration in the final sample yet.
We did try different radical optimizations. 10 mM seems to be the optimal. For 20 mM the enhancement goes down to 30.
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Hi Ribal, thank you for the presentation.
Did you try radicals of different types, do you think they might give a better enhancement? And, following the previous question by Chloé, do you have an explanation why increasing the concentration of the radical you used decreases the enhancement? -
Hi Arianna,
We did not try different radicals. The radical we used (ASYMPol-POK) is, to my latest knowledge, the best-performing and commercially available one at this field. There is a plan to try AMUPol and see the difference between both. In general, when you increase your radical concentration, you are adding more paramagnetic species to your sample (sometimes high concentration may also overcouple your radicals and can terminate them), which leads to more paramagnetic relaxation and broadening, and this can affect your enhancement.
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Hi Ribal, nice presentation! The different results depending on glassing agent used made me very curious, and I have a couple questions to this effect:
1) What would you expect to occur if you tried DMSO solvent?
2) There are some papers that use a special freezing method (https://www.jove.com/v/61733/cryogenic-sample-loading-into-magic-angle-spinning-nuclear-magnetic) that requires only 10-15% glycerol or DMSO for cryopreservation to run MAS DNP experiments without breaking cells:
https://pubs.acs.org/doi/full/10.1021/jacs.1c06680 and https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2021.789478/full — I am wondering if you would expect that decreasing glycerol content could potentially mimic the results you see in just insulin, while simultaneously providing some of the benefits of glycerol (which appear to be stronger signal based on the slide)
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