David Guarin's research while affiliated with Massachusetts General Hospital and other places

Publications (7)

Article
Full-text available
Dissolution dynamic nuclear polarization (DDNP) is a versatile tool to boost signal amplitudes in solution-state nuclear magnetic resonance (NMR) spectroscopy. For DDNP, nuclei are spin-hyperpolarized "ex situ" in a dedicated DNP device and then transferred to an NMR spectrometer for detection. Dramatic signal enhancements can be achieved, enabling...
Article
Full-text available
Dissolution dynamic nuclear polarization (D-DNP) experiments rely on the transfer of a sample between two high-field magnets. During this transfer, samples might experience passage through regions where the stray fields of the magnets are very weak, can approach zero, and even change their sign. This can lead to unexpected spectral features in spin...
Article
Long-lived imbalances of spin state populations can circumvent fast quadrupolar relaxation by reducing effective longitudinal relaxation rates by about an order of magnitude. This opens new avenues for the study of dynamic processes in deuterated molecules. Here we present an analysis of the relaxation properties of deuterated methyl groups CD3. Th...
Article
Dynamic nuclear polarization (DNP) embraces a family of methods to increase signal intensities in nuclear magnetic resonance (NMR) spectroscopy. Despite extensive theoretical work that allows one to distinguish at least five distinct mechanisms, it remains challenging to determine the relative weights of the processes that are responsible for DNP i...

Citations

... A significant fraction of the polarization was lost during sample dissolution and transfer due to fast relaxation during rapid low-field passage. 61 It should be noted, though, that solution-state enhancements depend critically on the layout of the laboratory where the DDNP system is situated and the effective magnetic fields during sample transfer. 62 The 3-to 4-fold prolonged relaxation times enable a similarly extended detection time window. ...
... 3. The µw irradiation is gated and a delay t g allows the electron spins to return to Boltzmann equilibrium [32,33]. ...
... 61 It should be noted, though, that solution-state enhancements depend critically on the layout of the laboratory where the DDNP system is situated and the effective magnetic fields during sample transfer. 62 The 3-to 4-fold prolonged relaxation times enable a similarly extended detection time window. This feature might be useful, for example, in DDNP experiments aiming to detect metabolic conversion of hyperpolarized substrates. ...
... We found that these conditions were necessary to generate MASER pulses. Besides, the complete absence of 2 H nuclei in the sample precluded repolarization of 1 H through a cross-talk mechanism, [33,20,18] in contrast with our previous study. [40] Finally, MASER pulses were not observed in the absence of continuous µw irradiation, which was deemed necessary in all cases in the present study. ...
... The relaxation mechanisms of LLS have been extensively studied 3,6,15,[60][61][62][63][64][65][66][67][68][69][70][71] . ...
... Therefore, depending on the DNP history of the sample, high polarizations of other nuclear spins may get transferred to the measured nuclear spins either by direct nuclear ? nuclear cross-relaxation (for example from abundant 2 H spins in the case of partially deuterated DNP samples) or by more complex electron spin mediated polarization transfers such as the four-spin cross-effect [14] or thermal mixing [105][106][107]. Such effects may significantly affect the build-up curves, but in principle not the final polarized steady state (if one waits long enough). ...