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Rapid Melting Strategies for benchtop DNP: A Step Toward Replenishable Hyperpolarization in Liquid-State NMR
Yang Wang (Very High Field NMR Center of Lyon (CRMN Lyon), France)
LinkedIn: @Yang Wang; X: @WangYan35529716; Bluesky: @yangwangcz.bsky.social
Abstract: Hyperpolarization techniques can boost NMR sensitivity by over 10,000-fold [1]. Among these, dissolution dynamic nuclear polarization (dDNP) is well established but suffers major drawbacks: it is destructive, single-use, and results in dilution upon sample dissolution, leading to rapid signal decay and incompatibility with multi-scan NMR experiments [2].
We are developing a benchtop DNP platform designed to enable replenishable hyperpolarization without dilution. This approach uses hyperpolarizing materials (HYPOPs) [3] within a compact benchtop polarizer [4], coupled directly to a benchtop NMR spectrometer for solution-state detection. Our long-term goal is a closed-loop system allowing repeated freeze-DNP-melt-flow cycles.
A critical challenge is maintaining polarization during the melt. In our current system, the sample is transferred from a 77 K DNP cryostat inside a 1 T benchtop polarizer into a dedicated melting station. This first prototype uses a guided high-flux (500 L/min), high-temperature (630 °C) air stream to melt a 250 µL sample in 5 seconds.
We are now working to reduce the melt time below 1 second by increasing airflow, temperature, and integrating high-power laser light. Ultimately, we aim to couple this rapid melt setup with DNP and solution-state hyperpolarized NMR for multi-scan acquisition capability.
References:
[1] Ardenkjær-Larsen, J. H., et al. PNAS 100.18 (2003): 10158-10163.
[2] Golman, K., et al. Cancer Res. 66.22 (2006): 10855-10860.
[3] El Daraï, T., Cousin, S.F., Stern, Q., et al. Nat. Commun. 12 (2021): 4695.
[4] Bocquelet, C., et al. Sci. Adv. 10 (2024): eadq3780.-
Hi Yang! Thank you for the presentation.
I was wondering if you observe any noticeable time lag associated with activating the heat gun during the melting process? If so, have you considered alternative heating methods, such as infrared or laser-based systems that might allow for a more rapid and controlled melt?
Regarding the freeze-melt and then flow cycles, how reproducible are your polarization levels across repeated runs?
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Hi Kshama,
Thank you for your questions !
Indeed, the heat gun does require a few seconds after activation to reach the target temperature. To address this, I preheat the gun to the desired temperature before exposing the sample, so that the hot air is already at the setpoint at the very start of the melting process.
I have also considered three alternative heating strategies. Among them, infrared laser heating is particularly promising. We have recently acquired a 1 kW, 1 μm wavelength IR laser system, which is currently being installed. I hope to begin testing it in the coming months and are looking forward to sharing new results with you.
In parallel, we are also simulating microwave heating approaches, although the heating speed appears to be limited in this case…
Regarding your question on reproducibility, we unfortunately do not yet have experimental data. However, we are planning a series of repeated melt-DNP experiments in the coming months to verify the polarization reproducibility across cycles.
Best regards,
Yang-
Sounds great Yang! All the best and thank you!
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Removing t1-noise in DNP-enhanced NMR at natural isotopic abundance using two-spin order filter
Quentin Reynard-Feytis (CEA Grenoble, France)
LinkedIn: @Quentin Reynard-Feytis
Abstract: Recent developments in MAS-DNP have dramatically enhanced the sensitivity of solid-state NMR, making it possible to perform increasingly complex experiments. Notably, this includes 13C–13C and 13C–15N correlation spectroscopy on powdered samples at natural isotopic abundance (NA), without the need for isotopic enrichment. Working with low-abundance nuclei also reduces dipolar truncation, thereby facilitating the observation of long-range polarization transfers. However, the potential of these techniques is often compromised by strong artefacts such as t₁-noise, which arises from instabilities during indirect evolution. Because t₁-noise is multiplicative, signals from abundant but uncorrelated nuclei can mask weaker cross-peaks, particularly problematic in NA samples where signal overlap is common.
In this study, we present a new approach to suppress t₁-noise in natural-abundance 13C–13C DQ-SQ correlation spectra. The method involves converting double-quantum (DQ) coherences into longitudinal two-spin order (zz-terms), followed by the application of a “zz-filter” to selectively remove magnetization from uncorrelated 13C spins. We describe the theoretical basis of the technique and demonstrate its application to both J-coupling and dipolar-based DQ-SQ experiments at NA. At 100 K, using a standard Bruker MAS-DNP system, we show that this filtering enables the clear identification of long-range cross-peaks previously obscured by noise. Furthermore, at 30 K on a helium-cooled MAS-DNP setup, where t₁-noise is typically more severe due to higher sensitivity, we observe substantial SNR improvements in the indirect dimension (up to 10×). These advances make it possible to acquire, for the first time, a reliable 13C–13C DQ-SQ spectrum at natural abundance and 30 K.
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Hi Quentin, great work and nice presentation! Could you elaborate how zz-filter distinguish between “correlated” and “uncorrelated” nuclei at the quantum mechanical level? What happens to the overall sensitivity when you apply this filtering – is there a trade-off between noise suppression and signal intensity?
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Hi Amit,
thank you very much !
before the DQ excitation block, the spins are prepared among the z-axis and from there you apply the DQ-excitation. At this stage, there is two possibilities:
– correlated spins: you generate DQCs (which are for instance DQy = I1xI2y + I2yI1x)
– uncorrelated spins: they cannot create DQCs so they stay along the z-axis
When we apply the zz-filter, we convert these terms such as:
– correlated spins: the first pulse will create I1zI2z terms from the DQy (cannot be completely converted)
– uncorrelated spins: the Iz magnetization is put in the x.y plan
The subsequent delay will diphase uncoupled spins’ Ix.y magnetization, but will preserve the I1zI2z terms that can only be formed from coupled spin pairs.
The second pulse will convert the I1zI2z terms back into DQCs, and the sequence keeps running 🙂
Let me know if that was clear or if you have any more questions !
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update: I forgot to answer the 2nd part of your question.
Yes, there is a trade-off. For isotropic DQ-excitation (i.e., all the DQCs generated have the same phase in the DQ subspace), we loose a factor 2 when applying the zz-filter.
This is problematic, although we obtain a 5 to 12-fold noise reduction with the zz-filter, which leads to SNR improvements of ~2.5 to 6.
When facing relatively “low” t1-noise, the applicability of the zz-filter isn’t straightforward and there might be other solution more viable. (for instance Fred Perras paper 10.1016/j.jmr.2018.11.008 )
I hope this was clear !
Best,
Quentin
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Thank you Quentin, for your detailed answer.
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Dear Quentin,
Thank you vor the very nice presentation!
I was wondering if the efficiency of the zz-filter depends on the refocused lifetime of the coherences (T2′) and/or on the spinning frequency ?
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Dear Chloé,
thank you very much for your comment !
You’re perfectly right, since we want the SQCs associated to uncoupled spins to diphase during the delay of the zz-filter, this needs to be done through various (Zeeman truncated) interactions: CSA, 1H-X couplings, 1H-1H couplings, etc…
Although all of these interactions are supposely averaged out by MAS, their still quite present in rather slow MAS speed regime (<10kHz). At higher spinning speeds, the time necessary to diphase the SQCs (which create the t1-noise) might be exceedingly high ! The T2' partially transcripts for how present these residual interactions influence the spectrum, so this is definitely linked ! A really long T2' might mean that the residual interactions are not strong enough to quickly diphase the SQCs, which can affect the zz-filter efficiency…
However:
– at natural abundance, the zz-terms lifetime is reeeaaaally long since they don't face spin diffusion issues, so in principle there is no limitation to extend the zz-filter delay.
– It is possible to add a DARR-field on the 1H channel, which reintroduces 1H-13C coupling, to speed up the decay of the SQCs during the zz-filter delay.
So in conclusion, yes it definitely matters and the stategy needs to be adapted, but one shouldn't face any major limitations….although this still needs to be proved 🙂
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Thank you for the detailed answer
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Role of Quantum Coherence in Chirped DNP
Mayur Manoj Jhamnani (New York University Abu Dhabi, United Arab Emirates)
LinkedIn: @Mayur Jhamnani; X: @mayur_jhamnani
Abstract: DNP is transforming NMR and MRI by significantly enhancing sensitivity through the transfer of polarization from electron spins to nuclear spins via microwave irradiation. However, the use of monochromatic continuous-wave irradiation limits the efficiency of DNP for systems with heterogeneous broad EPR lines. Broad-band techniques such as chirp irradiation offer a potential solution, particularly for Solid Effect (SE) DNP in such cases. Despite its widespread use, the role of quantum coherence generated during chirp irradiation remains unclear, even though it is a key factor in determining the maximum achievable DNP efficiency. In this work, we use density matrix formalism to provide a comprehensive understanding of the quantum coherence generated during non-adiabatic passages through electron-nucleus double-quantum (DQ) and zero-quantum (ZQ) SE transitions and their impact on Integrated Solid Effect DNP under chirp irradiation. Our analysis employs fictitious product-operator bases to trace the evolution of electron-nucleus coherence leading to integrated or differentiated SE. We also explore the role of decoherence in maximizing chirped DNP in microwave power or nutation frequency limited scenario. These findings provide an understanding of the role of coherence generated during pulsed-DNP and MAS-DNP at different temperature ranges. Our results reveal that quantum coherences generated during non-adiabatic passages critically determine whether the chirped DNP process yields Integrated Solid Effect (ISE), or Differential Solid Effect (DSE). By analyzing the evolution of the density matrix in DQ and ZQ subspaces, we show how coherence generation and its decay through decoherence play a decisive role in shaping the net DNP enhancement.
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Hello,
Could you clarify what you mean when you state that adiabatic pulses do not generate coherence, while non-adiabatic pulses generate coherence?
What would you say was the most surprising finding of your study? Is there a plan to confirm any of your theoretical findings experimentally?-
Hello,
Thanks for your question.
1. When the chirped MW irradiation is adiabatic (i.e., satisfies the Landau Zener condition for adiabaticity), an initial density matrix that is a polarization, Sz, undergoes complete inversion to -Sz. However, if the chirp is non-adiabatic, an initial density matrix that is a polarization, Sz, does not undergo complete inversion, rather, some coherence is generated.
2. Most surprising/important finding: We found that when the initial density matrix is a pure coherence (mSx + nSy)- an adiabatic pulse would lead to a generation of only coherence however, a non-adiabatic pulse would give both coherence and +/-polarization (sometimes +ve polarization is generated while other times -ve polarization is generated). This helped us explain the caveat between ISE and DSE in the paper: https://arxiv.org/html/2410.19170v1.
3. Regarding experiments – our findings are experimentally hard to validate as there are several effects, powder averaging and B1 field inhomogeneity.
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Hello Mayur, thank you for the presentation. It is a very interesting study.
Could you comment more about why a chirp pulse is never adiabatic between ZQ and DQ transitions? Does it depend on the available mw power (omega1) and how?
Why the decoherence process favours the ISE over the DSE?
Thank you. -
Hello,
Thanks for your question.
1. The MW chirp pulse can result in an adiabatic or non-adiabatic transition depending on the Landau-Zener (LZ) condition. The condition is that (pi*p^2) / 2k >> 1 for the chirp pulse to be adiabatic across a transition. Here p is the perturbation and k is the sweep rate.
For a single quantum transition, perturbation is just MW power (in the rotating frame). As a result, it is much easier to ensure adiabaticity. However, the perturbation for DQ and ZQ transition have the pseudo-secular hyperfine coupling term (B) in the denominator. This means, higher MW power (beyond the available MW power) is required to excite these resonances adiabatically.
2. The role of quantum coherence was causing the caveat between ISE and DSE. If the coherence is decayed, we can easily look at it from just a polarization standpoint. Since the SQ transition inverts the electron spin polarization from Sz to -Sz, the enhancement from the following ZQ transition will add to that from the DQ transition (leading to ISE). A detailed explanation is provided in https://arxiv.org/html/2410.19170v1.
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Hi Mayur, interesting talk! I am curious, what would you expect the results to look like if you assume relaxation and coupling parameters from various known radicals (e.g. Trityl, AMUPOL, P1 centers). Would the resulting DNP mechanism be strongly dependent on the couplings/relaxations expected within such radicals?
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Thank you for your reply Mayur.
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Seeing the unseen with Dynamic Nuclear Polarization
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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Slow Water in Engineered Nanochannels Revealed by Color-Center-Enabled Sensing
Rohma Khan (CUNY City College of New York, CUNY Graduate Center, United States)
Bluesky: @gbalavoi.bsky.social
Abstract: Characterization of nanoscale confinement of liquids via quantum sensing can overcome the sensitivity, spatial, and temporal limitations of other measurement techniques, allowing deeper understanding of dynamics central to areas spanning geophysics, tribology, catalysis, polymer science, and biology. Using shallow nitrogen vacancy (NV) centers as our quantum sensors we probe the molecular dynamics of water molecules confined within engineered ~5-nm-tall channels formed by a hexagonal boron nitride (hBN) structure on the diamond surface. Our resultant NV-enabled nuclear magnetic resonance spectra of confined water protons reveal a reduced H2O self-diffusivity, orders of magnitude lower than that in bulk water. Correlation measurements show us long lasting nuclear spin coherences, indicative of molecular dynamics intermediate between bulk water and ice. Molecular dynamics modeling indicate cluster formations may arise from accumulation of surface charge and carrier injection into the fluid under laser illumination. Our next step is the extension of these experiments to variable temperatures with preliminary findings showing narrowing of our NV NMR Spectra as we approach freezing point.
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Hi Rohma,
Excellent presentation. From the perspective of an organic chemist, I am curious if you could use the same system to detect protons in other solvents, such as organic solvents instead of water. Would you expect to observe different proton frequencies depending on the chemical structure of the solvents, and achieve NV-enabled H NMR? Thanks! -
Hello Yunfan Qiu,
Thank you for your question!
We can use the same system to detect protons in other solvents, in my colleague’s case he is able to detect protons in fluorinated oil. We have also tried this with PEG. In our system we would not be able to observe different proton frequencies depending on the chemical structure of the solvents, but others have with a slightly modified setup. Here is the citation for them Glenn, D., Bucher, D., Lee, J. et al. High-resolution magnetic resonance spectroscopy using a solid-state spin sensor. Nature 555, 351–354 (2018). https://doi.org/10.1038/nature25781
One of the key points in our system is that we work with statistical polarization but to see the chemical shifts we need thermally polarized nuclear spins. Please let me know if you have any further questions, thanks!
Rohma
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Hi Rohma, interesting presentation! I am wondering if there are good ways to optimize this technique without substantially changing the result. I am thinking of two ways:
1) Optimizing the diamond properties (e.g. number of NV centers, closeness of NV centers to the surface, size of the diamond, etc.)
2) Implementing Dynamic Nuclear Polarization via organic radicals being placed in the solvent and microwaves being shined onto the water to enhance the NV-NMR signal
I am curious about your thoughts on these two and whether you already know ways the diamond could be optimized or how compatible DNP could be with your methodology (would the radicals interfere too much with the end result?)
Thank you!
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Solid State Characterization of Co-amorphous, Co-crystal and Eutectic systems with Solid-state NMR
Shovik Ray (Indian Institute of Science, India)
LinkedIn: @Shovik Ray; X: @ray_shovik
Abstract: Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is an indispensable tool in pharmaceutical research that provides detailed structural and dynamic insights. This non-invasive technique is particularly critical for identification and quantification of polymorphs forms and tracking of local dynamics. Thus, SSNMR plays a key role at various stages of drug development from preformulation to manufacturing.
In this presentation, I will show the applications of SSNMR in characterization of co-amorphous systems, developed to enhance the solubility and dissolution rates of active pharmaceutical ingredients (APIs). In particular, the molecular interactions leading the co-amorphization of Dasatinib, a tyrosine kinase inhibitor used in chronic myeloid leukaemia therapy, with various co-amorphous systems will be discussed in detail. I will show the use of 1H, 13C and 1H-1H double quantum – single quantum correlation experiments to confirm presence or absence of inter- and intra-molecular hydrogen bonding, which is a key factor in determining formation of co-formers.
I will also discuss recent results on Venetocloax, which is a medication used to treat adults with chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL) or acute myeloid leukemia (AML). Our studies highlight the capabilities of SSNMR in combination with other characterization techniques to gain pivotal information and optimize pharmaceutical formulations.-
Hi Shovik, nice work! Could you briefly explain how you concluded that intramolecular interactions predominate in the DAS:MAL system based on the DQ-SQ data?
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Hi, Amit, thanks!
We have executed the DQ-SQ with a DQ excitation time such that, it corresponds to the distance of 1.8-2.3 Å (calculating corresponding H-H dipolar coupling), which is the conventional hydrogen bonding distance. We did get strong intermolecular interactions. But, for DAS-MAL case for the same mixing time I did not get inter-molecular peaks but intra-molecular peaks are present. Therefore, we concluded intra-molecular interaction is predominate in DAS:MAL system, whereas in DAS:SU the inter-molecular interaction is present.
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Thanks Shovik.
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Hi Shovik, nice study. How were the samples prepared – is there any impact of solvent on whether the co-amorphous or co-crystal systems will form? And did you try any other co-former with Ven?
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Hi Riley,
extremely sorry for the delayed response.
The samples were prepared by liquid assisted grinding method. Methanol was used as a solvent to co-grind them and to form the co-amorphous system. the impact of solvent we did not check explicitly but yes, if we see the “screening of the co-formers” section in. the poster, with nicotinic acid and phenanthrene, Dasatinib did not form a co-amorphous system, rather a co-crystal. Therefore, I think there is impact of solvent directing co-amorphization/crystallization process. For details please check out (https://doi.org/10.1039/D5CE00064E). We can have more discussions.
For Ven yes we are studying more co-formers also, and the study is in progress.
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Hi Shovik, interesting study! One question I have is with regards to your deconvolution. I see many different populations in your deconvolution, each with different heights, and was curious about how you performed your fitting procedure (I may have to do something similar for an EPR line in the near future so I could use a few pointers haha!)
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Hi Raj,
thank you for the question. Let me answer you genuinely.
The peaks were really broad even after echo-filtering. Therefore, we performed solution NMR to get the chemical shift assignments. Then based on that information and the nature of peaks we performed the deconvolution. The deconvolution was done on topspin (software provided by bruker) with a gaussian/lorentzian model. After initial guesses are given (based on the solution NMR data and their chemical nature), it fitted the spectra. We tried with multiple different initial guesses also, it turned out to be similar end point. So, that’s how we got the deconvolution. If unambiguity of deconvoluted peaks is a question, then to prove that we need the experiments to be done in high sample spinning.
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Gotcha! Thank you for describing how you did that in detail! That is very helpful to know. 🙂
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Hi Raj,
thank you for the question. Let me answer you genuinely.
The peaks were really broad even after echo-filtering. Therefore, we performed solution NMR to get the chemical shift assignments. Then based on that information and the nature of peaks we performed the deconvolution. The deconvolution was done on topspin (software provided by bruker) with a gaussian/lorentzian model. After initial guesses are given (based on the solution NMR data and their chemical nature), it fitted the spectra. We tried with multiple different initial guesses also, it turned out to be similar end point. So, that’s how we got the deconvolution. If unambiguity of deconvoluted peaks is a question, then to prove that we need the experiments to be done in high sample spinning.
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Solid-state NMR methods for characterization of ions embedded in graphenic materials for supercapacitors application
Paulo Cesar de Mello Correa (University of Espírito Santo (UFES), Brasil)
X: @pcmspin; Bluesky: @spinplus.bsky.social
Abstract: Solid-state NMR is widely employed to study the structural properties of activated carbon and other graphenic materials. Activated carbon is extensively utilized in industrial and consumer applications, particularly in energy storage devices such as supercapacitors, which serve as an environmentally sustainable alternative for integration into electrical systems alongside conventional batteries, or potentially replacing them in the future. In supercapacitor design, activated carbon functions as an electrode material due to its highly porous network, which provides a large surface area, thereby enhancing capacitance. Another approach to improving energy storage capacity of a supercapacitor involves synthesizing activated carbon with controlled pore dimensions, confining ions near the surface for optimized charge accumulation. Solid-state NMR can measure the nucleus-independent chemical shift (NICS), defined as the chemical shift difference (in ppm) between extra-pore and intra-pore peaks in NMR spectra. In this study, solid-state ¹H and ¹⁹F NMR spectra were acquired for activated carbon samples soaked in distilled water and aqueous solutions of NaF and NaBF₄. The results reveal an increase in NICS with surface area, consistent with steam activation that introduce micropores, which leads to larger NICS values, indicating reduced ion-surface distances. Furthermore, NMR spectral deconvolution of extra-pore and intra-pore peaks enables indirect estimation of pore volume for the carbon material.
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Thank you for the presentation. Have you considered using 10/11B NMR to study the BF4- ions?
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Hello Jonas!
It would really be interesting to measure with 11B and compare the results, thank you for the suggestion. We are also working to carry out measurements with 23Na and possibly confirm some particular aspect of the BF4 ion in accessing the pores of samples B240 and B400. In addition, this analysis would provide a perspective on a possible difference between cations and anions in accessing the pores of the studied material.
thank you for the comment!!
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Nice presentation Paulo. Adding on to Jonas’ Boron suggestion, have you thought to look at 23Na or 35/37Cl to see whether these ions show similar behaviour as the ones studied? Additionally, have you performed any VT NMR to try to assess ion dynamics in the activated carbon?
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Hello Riley!
Thank you for the suggestion, we do have plans to measure with 23Na (for the NaBF4 1.0 M solution) and possibly with 35/37Cl (for the LiCl 1.0 M solution) to investigate possible relationships with the ion charge (cation or anion) for accessing the porous network of the studied carbons, thank you for the suggestion. Although the results have already shown that Li+ and BF4- ions do not access the pores of the B240 and B400 samples, a more careful analysis is necessary to draw such conclusions. Regarding VT NMR measurements, unfortunately, we do not have the apparatus for this type of measurement. However, we are conducting Exchange NMR (EXSY) measurements to investigate the dynamic aspects of ions in the exchange regimes between the bulk electrolyte and the porous network, as well as in the intra-particle exchange regime.
Thank you very much for the comment!!
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Cool! I would be curious if the Na/Li and F/Cl would have similar behaviours, and the quadrupolar parameters (particularly for Cl) could be instructive on whether the Cl ions are more immobilized in the pores vs. bulk.
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Hello, it would be very interesting to analyze all the nuclei present in NaBF4 and LiCl. We are working on taking these measurements to complement our work. Thanks again for your comment!
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Hi Paulo,
Interesting presentation!
My question is quite simple: Is there any specific reason you chose 5 kHz MAS for your experiment?-
Hello Bijaylaxmi, interesting question!
There is indeed a reason: our experiments are being conducted using an unsealed rotor, which allows for potential solution leakage during centrifugation in the MAS experiment. To mitigate this, we are operating at a spinning frequency of 5 kHz. In fact, we are actively investigating this leakage through NMR measurements, using a method that enables us to monitor the decay in intensity of both the ex-pore and in-pore peaks over time. Our results confirm the occurrence of leakage, as evidenced by a consistent decrease in the ex-pore peak intensity, particularly within the first 15 minutes of spinning. Therefore, all measurements are carefully limited to under 15 minutes and using the lower spinning frequency possible to prevent damage to the spectrometer.
Thank you for the comment!!
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Nice work!
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Thanks for the presentation!
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Study of host-guess capacity of N-acylhydrazone-based macrocycles using NMR spectroscopy
Anca Gabriela Mirea (National Institute of Materials Physics, Romania)
Abstract: We present herein the synthesis of novel [2 + 2] and [3 + 3] N-acylhydrazone-based macrocycles using a pool of dialdehydes and dihydrazides. The macrocycles were used in various assays to investigate the hosting capacity of various guests using NMR.
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Hi Anca, interesting work! Could you please elaborate a bit more on how you inferred the triangular or tetragonal geometry using 2D NMR?
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Hy Amit! To elucidate the macrocyclic shape, we recorded 2D NMR (NOESY) indicating a triangular shape, according to the space interactions of protons within the molecule. The spectrum revealed NOE connectivity between NH and H (hydrazide moieties) protons, as well as CH=N and H (aldehyde moieties) protons. For more details you can read our article DOI: 10.1039/d4ta09035g.
Thank you very much for your interest! I appreciate your question!
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Hy Amit! To elucidate the macrocyclic shape, we recorded 2D NMR (NOESY) indicating a triangular shape, according to the space interactions of protons within the molecule. The spectrum revealed NOE connectivity between NH and H (hydrazide moieties) protons, as well as CH=N and H (aldehyde moieties) protons. For more details you can read our article DOI: 10.1039/d4ta09035g.
Thank you very much for your interest! I appreciate your question!
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Thanks Anca.
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Nice work Anca – why do you think the rectangular macrocycle readily took up F- and not Br-? What about Cl-? From your work, do you have any insights on what kind of synthetic considerations give rise to different macrocycle shapes?
Thanks!-
Hy Riley! The interaction of the rectangular macrocycle with TBAF may either lead to deprotonation of the hydroxyl and amide groups or cause
hydrogen bonding between the fluoride and the two groups.
The shape of the macrocycle depends on the precursors used for the synthesis.Thank you very much for your interest! I appreciate your question!
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The Quantum Gate Recipe: Simulation of Nuclear Magnetic Resonance Pulse Protocols for the CNOT and SWAP Quantum gates
Lena Aly (New York University Abu Dhabi, UAE)
LinkedIn: @Lena Aly
Abstract: In this work, we develop a MATLAB-based simulation model for NMR pulse protocols in weakly coupled spin-½ systems, with a focus on implementing quantum logic gates such as the Controlled-NOT (CNOT) gate. The model connects the unitary matrix representation of quantum gates to experimentally realizable pulse sequences using angular momentum operator formalism. It allows direct evaluation of pulse performance and provides quantitative error estimates for various sequences. The model enables informed comparisons between alternative pulse schemes, and lays the groundwork for future extensions to include advanced techniques such as composite pulses for NMR based quantum information science.
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Hi, what is the classical analogy of the CNOT gate, and what is the main difference between the two?
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Hi!
The action of the CNOT gate is analogous to the classical XOR operation, and the output of the XOR gate can be thought of as the target qubit in a CNOT. Unlike the XOR, however, the CNOT does not reduce the two qubits into one qubit: the control qubit remains as it is, and the target undergoes the XOR operation. This makes the operation of the CNOT reversible and can be represented by a unitary matrix, as required for all quantum gates.
It can be more challenging to implement the CNOT gate, though, because it is important to only flip the state of the target qubit without changing the coherence of the states.
Also, the CNOT is an essential component in implementing quantum entanglement, which is necessary to give quantum computers an advantage over their classical counterparts.
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Thank you for the presentation. How easily can this expanded to investigate e.g., the Toffoli gate?
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Such an interesting question!
The current work lays the framework for transforming the desired projection operators in the form of idempotents into realizable pulse sequences and testing them. Since any desired expansions would be unitary, they can also be modeled as idempotents and follow the same logic with a minor modification in the defined Hamiltonian.
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Hi Lena, nice presentation! I am curious, what are some examples of those small mistakes that could occur when trying to go from the matrices to the pulse sequences?
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Thank you so much!
Well, since the process of going from the matrices to pulse sequences includes identifying the desired projection operators, factorizing them to include complex numbers, using idempotent identities to rewrite them as exponents, and then trying to separate the exponents such that each exponent applies only to one axis, many mistakes could happen, especially with signs.
The one I identified in Price et al 1999 (https://doi.org/10.1006/jmre.1999.1851) using the program was in their application of the identity highlighted in the presentation. It was inconsistent with their choice of axis, which did not end well in the simulation as shown (they should have used U^-1 where they have used U). This also makes sense why their result was different from the one by Volkov and Salikhov 2011 (10.1007/s00723-011-0297-2), although they both used the same mathematical foundation to derive the pulse sequence for the CNOT gate.
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Thank you! That is very interesting–it turns out sign mistakes are crucial to avoid for these kinds of calculations!
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Toward Understanding of Nuclear Spin Relaxation at Zero-to-Ultralow Fields
Chengtong Zhang (New York University, United States)
Abstract: NMR experiments can interrogate a broad spectrum of molecular tumbling regimes and can accurately measure interatomic distances in solution with sub-nanometer resolution. Relaxation rates of nuclear spin polarization can unravel many dynamical and structural aspects of biomolecules in their native form. The high field relaxometry/dispersion techniques are widely used to monitor protein folding, molecular size, intermolecular interactions etc. However, little effort was devoted to extracting molecular information from relaxation rates at zero-to-ultralow-field (ZULF) mainly due to poor SNR and intricate spin dynamics. We develop the theoretical framework to understand relaxation rates measured in a ZULF-NMR setup with detection using optical-atomic magnetometers. In regimes where the scalar coupling constants and differences in Larmor frequencies of heteronuclear systems AX(N-1) have similar magnitudes, the spectrum reaches its maximum complexity with 2^N peaks. Populations and coherences’ lifetime measurements will greatly depend on the choice of monitored peaks’ decay. This multifaceted analysis of the same relaxation interaction can lead to a more accurate and robust determination of its strength and correlation time leading to new strategies for simultaneous extraction of structural and dynamical. We highlight how several factors impact the observed rates, such as (i) the shuttling profile from the (pre)polarizing magnet to the detection region, (ii) the measurement field, (iii) the detection method (single- or dual-channel) and even (iv) the nutation angle induced by the detection pulse. Our findings are compared to experimental relaxation rates measured for two [13C]-labelled molecules, showing how structural constraints and rotational tumbling can be inferred from ZULF relaxometry studies.
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Hello Chengtong, great presentation. This is very interesting with all of the different rates contributing. Can you comment on the origin of the two relaxation components (slow and fast)?
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Hi Blake! Thank you for your question! The two relaxation components were derived from a Bi exponential decay model by fitting the amplitude of the signal through storage time(The time we wait for polarization). And the model of the Bi exponential decay was from the population evolution, via the dipole-dipole interaction in the relaxation mechanism.
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Understanding the differential RNA-binding of HuD isoforms through conformational dynamics using solution NMR spectroscopy
Nikhil Sunny (IISER Pune, India)
LinkedIn: @Nikhil Sunny; X: @Nikhil__Sunny__
Abstract: HuD is an RNA-binding protein (RBP) essential for neuronal development and glucose homeostasis. It has tandemly arranged three RNA recognition motifs (RRMs). Multiple isoforms, namely, HuD A, HuD B, and HuD D—have been reported that are differentially expressed in various tissues. The A and B isoforms both feature an unstructured N-terminal region; however, the A isoform has five additional amino acids when compared to the B isoform. This difference significantly impacts the RNA-binding and translation of insulin 2 mRNA. While the structure of HuD RRM12 is known, it does not include the unstructured N-terminal region, creating a gap in understanding its role in RNA targeting. In this study, we focus on understanding the role of the unstructured N-terminal region of A and B isoforms in the RNA-binding activity of the RRM1 domain by using NMR-based dynamics experiments and other biophysical techniques. FOur preliminary results show that the presence of the N-terminal leads to line-broadening and the disappearance of peaks in the 2D 15N-1H HSQC spectra. The disappeared peaks are mainly from the N-terminal region and the possible site of intra- and/or intermolecular interactions. In the presence of the N-terminal region, CSP is found in or near the RNP motifs of RRM1, which are the sites for RNA binding. We believe that this study will provide insights into how intrinsically disordered regions affect the intrinsic dynamics and RNA-binding activity of the RRM.
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Interesting!
Although I believe you are planning on further experiments to confirm the interaction of the N-ter with the folded domain, can you comment on the effect it could have on the binding to RNA?
Also, how do the R1 and R2 of the N-ter tail evolve as a function of residue number?-
1) The RNA-binding region can either be masked, reducing overall binding affinity, or it can function as an auxiliary region that enhances binding affinity. Since this RNA recognition motif (RRM) is a weak binder, we are working on optimizing the experimental parameters for the binding studies. I suspect it will act as an auxiliary region facilitating RNA binding, as shown from EMSA studies on Isoforms of HuD (full-length)(https://doi.org/10.1371/journal.pone.0194482)
2) “R1 and R2 of the N-ter tail evolve as a function of residue number.” I haven’t done those experiments. That’s the next part of my project.
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Interesting work:
What type of experiments you are planning to look for exact functional role of this protein?
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I will be doing in vitro studies only; majorly binding studies with RNA using ITC, NMR, fluorescence, etc.
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UV-Induced PET Depolymerization in m-Cresol Monitored by Time-Resolved Diffusion NMR on a Benchtop Spectrometer
Farwa Khalid (Insitute of physical chemistry, Polish Academy of Sciences, Poland)
Abstract: PET (polyethylene terephthalate) is commonly used in bottles, fabrics, and packaging due to its transparency, durability, and mechanical properties. Its extensive use, combined with its natural degradation under sunlight and UV rays, slowly and uncontrollably contributes to environmental pollution [1]. Efforts to address waste PET face challenges in achieving energy-efficient and selective depolymerization through physical sorting or existing chemical methods[2]. The depolymerization of PET in m-cresol under UV light is key to breaking it down into valuable monomers[3].
This study investigates UV-induced depolymerization of PET in m-cresol, focusing on real-time monitoring with Benchtop NMR. A flow-based experimental setup ensures continuous UV light exposure, while Diffusion NMR provides insights into diffusion properties and molecular size distribution during the process. Real-time diffusion data reveals the depolymerization kinetics, transitioning from high-molecular-weight polymer chains to low-molecular-weight monomers. This method offers valuable insights into the mechanistic pathway of PET depolymerization, potentially improving sustainable plastic waste management.
References
[1] F. Cao, L. Wang, R. Zheng, L. Guo, Y. Chen, and X. Qian, “Research and progress of chemical depolymerization of waste PET and high-value application of its depolymerization products,” Nov. 03, 2022, Royal Society of Chemistry. doi: 10.1039/d2ra06499e.
[2] S. Zhang et al., “Selective depolymerization of PET to monomers from its waste blends and composites at ambient temperature,” Chemical Engineering Journal, vol. 470, Aug. 2023, doi: 10.1016/j.cej.2023.144032.
[3] S. S. Karim et al., “Model analysis on effect of temperature on the solubility of recycling of Polyethylene Terephthalate (PET) plastic,” Chemosphere, vol. 307, Nov. 2022, doi: 10.1016/j.chemosphere.2022.136050.-
Hi Farwa, I have a question regarding the interpretation of DOSY experiments. In case of signal overlap, under which conditions is it possible to distinguish the two overlapping components? Would a signal display mono or biexponential decay? Thank you.
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I have used a PGSTE-WET to suppress the solvent signals interfering with the PET peaks. Selecting a gradient strength value where the interfering signal is attenuated and only the desired signal appears. This way, I filter out the solvent peaks in the DOSY spectrum.Also, we are using Tailored fitting Normalization to get the polydispersity index.
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Hi Farwa, great presentation. How does the wavelength of UV light influence the results you see?
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Hi,
The wavelength of the UV light greatly affects the photodegradation. I even tried the experiment with 270nm wavelength, but I didn’t see the degradation efficiently, even though this one has high energy, because PET shows maximum absorption closer to 300-320nm due to the aromatic ring and ester group. In 270 nm, I did not see the degradation product (Monomer) peak in the region around 9ppm, as it is shown in 365nm proton NMR spectra in my presentation and also I have calculated the peak area of the polymer peak its almost constant in 270nm.
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