A Metabonomic View on Wilms Tumor by High-Resolution Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Pediatric cancer NMR-metabonomics might be a powerful tool to discover modified biochemical pathways in tumor development, improve cancer diagnosis, and, consequently, treatment. Wilms tumor (WT) is the most common kidney tumor in young children whose genetic and epigenetic abnormalities lead to cell metabolism alterations, but, so far, investigation of metabolic pathways in WT is scarce. We aimed to explore the high-resolution magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) metabonomics of WT and normal kidney (NK) samples. For this study, 14 WT and 7 NK tissue samples were obtained from the same patients and analyzed. One-dimensional and two-dimensional HR-MAS NMR spectra were processed, and the one-dimensional NMR data were analyzed using chemometrics. Chemometrics enabled us to elucidate the most significant differences between the tumor and normal tissues and to discover intrinsic metabolite alterations in WT. The metabolic differences in WT tissues were revealed by a validated PLS-DA applied on HR-MAS T2-edited 1H-NMR and were assigned to 16 metabolites, such as lipids, glucose, and branched-chain amino acids (BCAAs), among others. The WT compared to NK samples showed 13 metabolites with increased concentrations and 3 metabolites with decreased concentrations. The relative BCAA concentrations were decreased in the WT while lipids, lactate, and glutamine/glutamate showed increased levels. Sixteen tissue metabolites distinguish the analyzed WT samples and point to altered glycolysis, glutaminolysis, TCA cycle, and lipid and BCAA metabolism in WT. Significant variation in the concentrations of metabolites, such as glutamine/glutamate, lipids, lactate, and BCAAs, was observed in WT and opened up a perspective for their further study and clinical validation.

Making the invisible visible: fast magic-angle-spinning NMR reveals the evasive hepatitis B virus capsid functional C-terminal domain

Experimentally determined protein structures often feature missing domains. One example is the C terminal domain (CTD) of the hepatitis B virus capsid protein, a functionally central part of this assembly, crucial in regulated nucleic-acid interactions, cellular trafficking, nuclear import, particle assembly and maturation. However, its structure remained elusive to all current techniques, including NMR. Here we show that the recently developed proton-detected fast magic-angle-spinning solid-state NMR at >100 kHz MAS is a game changer that allows to detect this domain and unveil its structural and dynamic behavior. We describe the experimental framework used and compare the domain’s behavior in different capsid states. The developed approaches extend solid-state NMR observations to residues characterized by large-amplitude motion on the microsecond timescale, and shall allow to shed light on other flexible protein domains still lacking their structural and dynamic characterization.

Spectroscopic evaluation of UVI–cement mineral interactions: ettringite and hydrotalcite

Portland cement based grouts used for radioactive waste immobilization contain high replacement levels of supplementary cementitious materials, including blast-furnace slag and fly ash. The minerals formed upon hydration of these cements may have capacity for binding actinide elements present in radioactive waste. In this work, the minerals ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and hydrotalcite (Mg6Al2(OH)16CO3·4H2O) were selected to investigate the importance of minor cement hydrate phases in sequestering and immobilizing UVI from radioactive waste streams. U L III-edge X-ray absorption spectroscopy (XAS) was used to probe the UVI coordination environment in contact with these minerals. For the first time, solid-state 27Al magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy was applied to probe the Al coordination environment in these UVI-contacted minerals and make inferences on the UVI coordination, in conjunction with the X-ray spectroscopy analyses. The U L III-edge XAS analysis of the UVI-contacted ettringite phases found them to be similar (>∼70%) to the uranyl oxyhydroxides present in a mixed becquerelite/metaschoepite mineral. Fitting of the EXAFS region, in combination with 27Al NMR analysis, indicated that a disordered Ca- or Al-bearing UVI secondary phase also formed. For the UVI-contacted hydrotalcite phases, the XAS and 27Al NMR data were interpreted as being similar to uranyl carbonate, that was likely Mg-containing.

1H detection and dynamic nuclear polarization–enhanced NMR of Aβ1-42 fibrils

Several publications describing high-resolution structures of amyloid-β (Aβ) and other fibrils have demonstrated that magic-angle spinning (MAS) NMR spectroscopy is an ideal tool for studying amyloids at atomic resolution. Nonetheless, MAS NMR suffers from low sensitivity, requiring relatively large amounts of samples and extensive signal acquisition periods, which in turn limits the questions that can be addressed by atomic-level spectroscopic studies. Here, we show that these drawbacks are removed by utilizing two relatively recent additions to the repertoire of MAS NMR experiments—namely, 1H detection and dynamic nuclear polarization (DNP). We show resolved and sensitive two-dimensional (2D) and three-dimensional (3D) correlations obtained on 13C,15N-enriched, and fully protonated samples of M0Aβ1-42 fibrils by high-field 1H-detected NMR at 23.4 T and 18.8 T, and 13C-detected DNP MAS NMR at 18.8 T. These spectra enable nearly complete resonance assignment of the core of M0Aβ1-42 (K16-A42) using submilligram sample quantities, as well as the detection of numerous unambiguous internuclear proximities defining both the structure of the core and the arrangement of the different monomers. An estimate of the sensitivity of the two approaches indicates that the DNP experiments are currently ∼6.5 times more sensitive than 1H detection. These results suggest that 1H detection and DNP may be the spectroscopic approaches of choice for future studies of Aβ and other amyloid systems.

Metal-Free Pyrene-Based Conjugated Microporous Polymer Catalyst Bearing N- and S-Sites for Photoelectrochemical Oxygen Evolution Reaction

The development of an efficient, sustainable, and inexpensive metal-free catalyst for oxygen evolution reaction (OER) via photoelectrochemical water splitting is very demanding for energy conversion processes such as green fuel generators, fuel cells, and metal-air batteries. Herein, we have developed a metal-free pyrene-based nitrogen and sulfur containing conjugated microporous polymer having a high Brunauer-Emmett-Teller surface area (761 m2 g−1) and a low bandgap of 2.09 eV for oxygen evolution reaction (OER) in alkaline solution. The π-conjugated as-synthesized porous organic material (PBTDZ) has been characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state 13C (cross-polarization magic angle spinning-nuclear magnetic resonance) CP-MAS NMR, N2 adsorption/desorption analysis, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) experiments. The material acts as an efficient catalyst for photoelectrochemical OER with a current density of 80 mA/cm2 at 0.8 V vs. Ag/AgCl and delivered 104 µmol of oxygen in a 2 h run. The presence of low bandgap energy, π-conjugated conducting polymeric skeleton bearing donor heteroatoms (N and S), and higher specific surface area associated with inherent microporosity are responsible for this admirable photoelectrocatalytic activity of PBTDZ catalyst.

Ionic Conductivity of Nanocrystalline and Amorphous Li10GeP2S12: The Detrimental Impact of Local Disorder on Ion Transport

Solid electrolytes with extraordinarily high Li-ionic conductivities are key for high performance all-solid-state batteries. So far, the thiophosphate Li10GeP2S12 (LGPS) belongs to the best Li ion conductors with an ionic conductivity exceeding 10 mS cm–1 at ambient. Recent molecular dynamics simulations performed by Dawson and Islam predict that the ionic conductivity of LGPS can be further enhanced by a factor of three if the crystallite size is reduced to the nanometer regime. A change in local ion coordination, hence local disorder, has been assumed to facilitate Li diffusion in the ab-plane of LGPS. As yet, no experimental evidence exists supporting this fascinating prediction. Here, we synthesized nanocrystalline LGPS by high-energy ball milling, characterized the material structurally and probed the Li+ ion transport parameters. Whereas X-ray powder diffraction and high-resolution 31P and 6Li magic angle spinning nuclear magnetic resonance (NMR) spectroscopy helped us to determine morphological changes and local structures upon milling, broadband conductivity spectroscopy in combination with electric modulus measurements allowed us to precisely follow the changes in Li+ ion dynamics. Surprisingly and against the behavior of other electrolytes, ionic conductivity turned out to decrease with increasing milling time, finally leading to a reduction of σ20°C by almost a factor of 10. This decrease affects both, bulk ion dynamics and total conductivity, which also comprises Li+ transport across grain boundary regions in LGPS. As could be shown by NMR, ball-milling leads to a structurally heterogeneous sample with the nm-sized LGPS crystallites being embedded in an amorphous matrix. This amorphous phase is responsible for the reduced performance of the milled electrolyte. Importantly, careful separation of the amorphous and (nano)crystalline contributions to the overall ionic conductivity revealed that even in the nanocrystalline regions Li+ ion dynamics is slowed down compared to untreated, coarse-grained LGPS. We conclude that defects introduced into the LGPS bulk structure via ball milling have a negative impact on ionic transport. We postulate that such kind of structural disorder is detrimental to fast ion transport in materials whose transport properties rely on crystallographically well-defined diffusion pathways.