Dynamic Nuclear Polarization and Other Magnetic Ideas at EPFL

Abstract

Although nuclear magnetic resonance (NMR) can provide a wealth of information, it often suffers from a lack of sensitivity. Dynamic Nuclear Polarization (DNP) provides a way to increase the polarization and hence the signal intensities in NMR spectra by transferring the favourable electron spin polarization of paramagnetic centres to the surrounding nuclear spins through appropriate microwave irradiation. In our group at EPFL, two complementary DNP techniques are under investigation: the combination of DNP with magic angle spinning at temperatures near 100 K ('MAS-DNP'), and the combination of DNP at 1.2 K with rapid heating followed by the transfer of the sample to a high-resolution magnet ('dissolution DNP'). Recent applications of MAS-DNP to surfaces, as well as new developments of magnetization transfer of (1)H to (13)C at 1.2 K prior to dissolution will illustrate the work performed in our group. A second part of the paper will give an overview of some 'non-enhanced' activities of our laboratory in liquid- and solid-state NMR.

Toward protein NMR at physiological concentrations by hyperpolarized water—Finding and mapping uncharted conformational spaces

“…To obtain NMR spectra of MAX at physiological concentrations in hyperpolarized water, we used dissolution DNP (DDNP) (36)(37)(38). We followed the protocol detailed in (39,40).…”

Spin Noise Detection of Nuclear Hyperpolarization at 1.2 K

“…Spin noise power spectra were acquired using a home‐built polarizer and probe described previously using a 6.7 T magnet equipped with a continuous flow helium cryostat and a doubly tuned ( 1 H and 13 C) saddle–coil probe with a proton resonance frequency of 285.23 MHz. Continuous‐wave microwave irradiation was performed at frequencies 187.5> f μw >188.5 GHz with a power p μw ≈80 mW.…”

Hyperpolarized NMR Spectroscopy: d‐DNP, PHIP, and SABRE Techniques

“…Recently, cross‐polarization (CP) pulse sequences have been coupled to d ‐DNP to boost its performance in the DNP of low‐γ nuclei, such as 13 C or 15 N atoms, by transferring the often‐higher and faster‐building polarization of 1 H nuclei to the low‐γ nuclei. Polarization levels of up to P ( 13 C)≈70 % within about 20 min have been achieved . Under d ‐DNP conditions, suspending (gating) the microwave irradiation during the CP contact can improve the efficiency …”

“…Polarization levels up to P ( 13 C) ≈ 70% in ca. 20 min [23,24] have been achieved. In d -DNP conditions, suspending (gating) the microwave irradiation during the CP contact can improve the efficiency.…”