The EFG Rosetta Stone: Translating between DFT calculations and solid state NMR experiments

We present a comprehensive study on the best practices for integrating first principles simulations in experimental quadrupolar solid-state nuclear magnetic resonance (SS-NMR), exploiting the synergies between theory and experiment for achieving the optimal interpretation of both. Most high performance materials (HPM), such as battery electrodes, exhibit complex SS-NMR spectra due to dynamic effects or amorphous phases. NMR crystallo reliable, accurate, efficient computational methods for calculating NMR observables from first prin ciples for the transfer between theoretical material structure models and the interpretation of their experimental SS-NMR spectra. NMR-active nuclei within HPMs are routinely probed by their chemical shielding anisotropy (CSA). However, several nuclear isotopes of interest, e.g. 7Li and 27Al, have a nuclear quadrupole and experience additional interactions with the surrounding electric field gradient (EFG). The quadrupolar interaction is a valuable source of information about atomistic structure, and in particular, local symmetry, complementing the CSA. As such, there is a range of different methods and codes to choose from for calculating EFGs, from all-electron to plane wave methods. We benchmark the accuracy of different simulation strategies for computing the EFG tensor of quadrupolar nuclei with plane wave density functional theory (DFT) and study the impact of the material structure as well as the details of the simulation strategy. Especially for small nuclei with few electrons, such as 7Li, we show that the choice of physical approximations and simulation parameters has a large effect on the transferability of the simulation results. To the best of our knowledge, we present the first comprehensive reference scale and literature survey for 7Li quadrupolar couplings. The results allow us to establish practical guidelines for developing the best simulation strategy for correlating DFT to experimental data extracting the maximum benefit and information from both, thereby advancing further research into HPMs

Magnetism and electrical and thermal transport in the natural Fe_1-xMn_xWO₄ (x=0.2) mineral from Potosí, Bolivia

The composition of a natural single crystalline specimen from the province of Potosi in Bolivia is found to be Fe0.8Mn0.2WO4. It crystallizes with the primitive monoclinic NiWO4 structure type [space group P2/c, a = 4.74751(6) angstrom, b = 5.71335(7) angstrom, c = 4.96847(5) angstrom, beta = 90.15(1)degrees]. Magnetic susceptibility and specific heat capacity measurements indicated that the mineral undergoes multiple magnetic transitions: T-N1 approximate to T-N1(cp) = 67(1) K, T-N2 = 28(3) K, and T-N2(cp) = 8(1) K. The reduced magnetic entropy of approximate to R ln 3 upon the high-temperature antiferromagnetic ordering suggests the failure of the simplified LS-coupling scheme in the description of the magnetism. Fe0.8Mn0.2WO4 is characterized by enlarged electrical resistivity showing an exponential decrease with temperature for T > 300 K, from which an energy gap of 310 meV is deduced. The well-pronounced maximum occurring in the phononic thermal conductivity just below the T-N1 is described by the Debye-Callaway model, indicating the dominance of phonon scattering on defects as well as umklapp processes

Temporal phosphoproteomics reveals circuitry of phased propagation in insulin signaling

Insulin is a pleiotropic hormone that elicits its metabolic and mitogenic actions through numerous rapid and reversible protein phosphorylations. The temporal regulation of insulin's intracellular signaling cascade is highly complex and insufficiently understood. We conduct a time-resolved analysis of the global insulin-regulated phosphoproteome of differentiated human primary myotubes derived from satellite cells of healthy donors using high-resolution mass spectrometry. Identification and tracking of ~13,000 phosphopeptides over time reveal a highly complex and coordinated network of transient phosphorylation and dephosphorylation events that can be allocated to time-phased regulation of distinct and non-overlapping subcellular pathways. Advanced network analysis combining protein-protein-interaction (PPI) resources and investigation of donor variability in relative phosphosite occupancy over time identifies novel putative candidates in non-canonical insulin signaling and key regulatory nodes that are likely essential for signal propagation. Lastly, we find that insulin-regulated phosphorylation of the pre-catalytic spliceosome complex is associated with acute alternative splicing events in the transcriptome of human skeletal muscle. Our findings highlight the temporal relevance of protein phosphorylations and suggest that synchronized contributions of multiple signaling pathways form part of the circuitry for propagating information to insulin effector sites