Session WOD. There are 5 abstracts in this session.

Session: HYPERPOLARIZATION 2, time: 10:45 - 11:00 am

Targetable DNP Polarization Agents for the Cellular Milieu

Byung Joon Lim; Bryce Ackermann; Galia Debelouchina
UCSD, La Jolla, CA

DNP has shown great promise as a tool to enhance the NMR signals of proteins in the cellular environment. As the sensitivity increases, the ability to efficiently polarize a specific macromolecule over the cellular background has become desirable. To address this need we present a tetrazine-based DNP polarization agent that can be targeted selectively to proteins containing the unnatural amino acid norbornene-lysine. Our approach is bio-orthogonal and easily adaptable to any protein of interest. We illustrate the scope of our methodology and investigate the DNP polarization transfer mechanisms in several biological systems. Our results shed light on the complex polarization transfer pathways in targeted DNP and pave the way to selective DNP-enhanced NMR spectroscopy in both bacterial and mammalian cells.

Session: HYPERPOLARIZATION 2, time: 11:00 - 11:15 am

Quantitative scaling analyses for non-Boltzmann spin polarization transfer

Nathan Prisco1; Arthur Pinon2; Lyndon Emsley2; Brad Chmelka1
1UC Santa Barbara, Santa Barbara, CA; 2EPFL, Lausanne, Switzerland

DNP-enhanced 1H spin diffusion analyses can be used to measure the dimensions of disordered surface domains over challenging <1 nm to 100’s nm length scales. Such analyses rely on quantitative models of DNP polarization transfer which are difficult to implement. Here, we introduce a constitutive equation that quantitatively describes polarization transfer across inhomogeneous magnetic field gradients (i.e., the spin-diffusion barrier) and between dissimilar material interfaces. These data and analyses provide compelling evidence for the existence and physical significance of a spin-diffusion barrier which limits polarization transfer when 1H-1H dipole-dipole couplings are weak. Additionally, analytical expressions are obtained for the steady-state enhancement (ε) and characteristic build-up time (TDNP) which are practically useful in selecting DNP formulations that yield optimal sensitivity improvements.     

Session: HYPERPOLARIZATION 2, time: 11:15 - 11:30 am

Overcoming Obstacles in ODNP: Studying Hydration Water of New Chemical Systems via Adaptable NMR Spectrometer

Alec Beaton; John Franck
Syracuse University, Syracuse,

Implementing ODNP to study the hydration dynamics of spin-labeled proteins and other related systems is well established. However, extending ODNP to study other interesting systems often requires non-trivial modification of the NMR instrumentation. We report here work toward systematizing the construction of an adaptable NMR spectrometer in the ODNP instrument that facilitates the study of various new chemical systems. Home-built Python libraries permit facile implementation of complex pulse sequences as well as processing techniques, both of which we demonstrate by acquiring 2D relaxometry data that is processed by an efficient, parallelized implementation of the 2-Dimensional Inverse Laplace Transform (2D-ILT) algorithm. We report results for two simple but important model systems: water-surfactant reverse micelles and cells expressing the Aer transmembrane protein.

Session: HYPERPOLARIZATION 2, time: 11:30 - 11:45 am

Assessing site-specific water accessibility in folded and unfolded proteins using hyperpolarization-enhanced 2D HMQC NMR

Or Szekely1; Greg L. Olsen1, 2; Mihajlo Novakovic1; Rina Rosenzweig1; Lucio Frydman1
1Weizmann Institute of Science, Rehovot, Israel; 2University of Vienna, Vienna, Austria

Hyperpolarized water ("HyperW") NMR is an emerging experiment whereby protein amide exchanges deliver 2D 1H-15N correlations with enhanced sensitivity. We applied HyperW NMR to proteins exhibiting a gamut of behaviors, ranging from disordered to fully folded. For most proteins the HyperW enhancements correlated well with solvent exposure considerations. Unexpected, however, was the behavior of drkN-SH3, a protein interconverting between folded and unfolded forms: for it, HyperW preferentially enhanced the folded state residues over the unfolded ones. These enhancements could only be explained by certain specific cross-relaxation conditions, or by invoking that faster rates of solvent exchange characterize folded sites than their unfolded counterparts. Factors that could explain such behavior –which has been theoretically proposed but is highly unorthodox– are discussed.

Session: HYPERPOLARIZATION 2, time: 11:45 - 12:00

Surface Mediated Hyperpolarization of Liquid Water from Parahydrogen

Yong Du1; Tommy Zhao1; Evan Zhao1; Ranjan Behera1; Raghu Maligal-Ganesh1; Wenyu Huang2, 3; Clifford Bowers1
1Department of Chemistry, University of Florida, Gainesville, FL; 2Department of Chemistry, Iowa State University, Ames, IA; 3Ames Laboratory, Department of Energy, Ames, IA

In 2018 we demonstrated that Pt3Sn intermetallic nanoparticles (iNPs) can mediate the alignment of proton magnetic moments in water, methanol and ethanol molecules from parahydrogen. This effect is referred as SWAMP (Surface Waters Are Magnetized by Parahydrogen). The hydroxy protons in water and alcohols exhibit stimulated emission NMR signals after only a few seconds of bubbling p-H2 gas through a suspension of the iNPs. Non-exchangeable methyl and methylene protons are also hyperpolarized in methanol and ethanol, respectively. Here, details about SWAMP nanoparticles, systematic studies, density matrix formulation of the mechanism as well as challenges will be presented. SWAMP-hyperpolarized liquids are free of radicals and catalyst residues, which could potentially be generalized to biomolecules with exchangeable protons for future MRI study.