NMR Spectroscopic Assignment of Backbone and Side‐Chain Protons in Fully Protonated Proteins: Microcrystals,Sedimented Assemblies,and Amyloid Fibrils

We demonstrate sensitive detection of alpha protons of fully protonated proteins by solid‐state NMR spectroscopy with 100–111 kHz magic‐angle spinning (MAS). The excellent resolution in the Cα‐Hα plane is demonstrated for 5 proteins, including microcrystals, a sedimented complex, a capsid and amyloid fibrils. A set of 3D spectra based on a Cα–Hα detection block was developed and applied for the sequence‐specific backbone and aliphatic side‐chain resonance assignment using only 500 μg of sample. These developments accelerate structural studies of biomolecular assemblies available in submilligram quantities without the need of protein deuteration.     

Anisotropy‐assisted non‐scattering coherent absorption of surface plasmon‐polaritons

The ability to control propagation of electromagnetic guided modes lies at the heart of integrated nanophotonics. Surface plasmon‐polaritons are a class of guided modes which can be employed in integrated optical systems. Here, we present a theoretical design of a coherent surface plasmon absorber which can perfectly harvest energy of coherently incident surface plasmons without parasitic scattering into free space modes. Excitation of free space modes which usually accompanies scattering of a surface plasmon by an interface boundary is avoided due to specially tailored anisotropy of the absorber. The concept of coherent SPP absorber is analyzed numerically for spatially non‐uniform and finite‐size structures. We believe that our results will be important for the development of integrated nanoplasmonic systems.     

Mathematical Working Spaces in schooling: an introduction

ZDM – Mathematics Education - The theoretical and methodological model of Mathematical Working Space (MWS) is introduced in this paper. For over 10 years, the model has been the...     

Periodic local MP2 method for the study of electronic correlation in crystals: Theory and preliminary applications

A computational technique for solving the MP2 equations for periodic systems using a local-correlation approach and implemented in the CRYSCOR code is presented. The Hartree-Fock solution provided by the CRYSTAL program is used as a reference. The motivations for the implementation of the new code are discussed, and the techniques adopted are briefly recalled. With respect to the original formulation (Pisani et al., J Chem Phys 2005, 122, 094113), many new features have been introduced in CRYSCOR to improve its efficiency and robustness. In particular, an adaptation of the density fitting scheme to translationally periodic systems is described, based on Fourier transformation techniques. Three examples of application are provided, concerning the CO(2) crystal, proton transfer in ice XI, and the adsorption of methane on MgO (001). The results obtained with the periodic LMP2 method for these systems appear more reliable than the ones obtained using density functional theory.     

Olefin exchange-mediated cyclopropanation of nitriles with homoallylic alcohols

We report herein olefin exchange-mediated cyclopropanation of nitriles with homoallylic alcohols. The use of homoallylic alcohols is central to the successful implementation.     

RbSb2 – Eine mit KSb2 verwandte Zintl‐Phase

RbSb₂ – A Zintl Phase related to KSb₂ The electron‐precise Zintl compound RbSb₂, which was known to melt incongruently at 418 °C, has been prepared in pure phase from elemental rubidium and antimony in sealed tantalum crucibles. In accordance with the ribbon‐shaped antimonide anions, the compound crystallizes with extremely thin intergrown, mechanically and chemically very sensitive needles of dark‐metallic lustre. The crystal structure could be determined and refined using single crystal x‐ray data (monoclinic, space group C2/m, a = 1403(2), b = 414.0(4), c = 855.7(14) pm, β = 104.45(12)°, Z = 4, R1 = 0.0901) despite the poor quality of the crystals. It shows fused six‐membered rings of two‐ and three‐bonded Sb atoms forming ribbons running along the monoclinic b axis, which can be interpreted as sections of the elemental structure of antimony (d_Sb‐Sb = 281.9(5) and 286.0(9) pm respectively). The structure of RbSb₂ is thus closely related to that of KSb₂, which exhibits identical antimony anions. Compared to the potassium compound, the ribbons are reoriented against each so that the coordination number of the A counter ions is increased from 6 + 2 (for A = K) to 8 + 2 (for A = Rb). The results of a FP‐LAPW band structure calculation of RbSb₂ are used to explain the chemical bonding in this classical Zintl phase with a calculated indirect band gap of 0.38 eV.     

Organized formation of 2D extended covalent organic frameworks at surfaces

The development of nanoscale masking for particle deposition is exceedingly important to push the future of nanoelectronics beyond the current limits of lithography. We present the first example of ordered hexagonal covalent nanoporous structures deposited in extended arrays of near monolayer coverage across a Ag(111) surface. The networks were formed from the deposition of the reagents from a heated molybdenum crucible between 370 and 460 K under ultrahigh vacuum (UHV) onto a cleaned Ag(111) substrate and imaged using a scanning tunneling microscope (STM). Two surface covalent organic frameworks (SCOFs) are presented; the first is formed from the deposition of 1,4-benzenediboronic acid (BDBA) and its dehydration to form the boroxine-linked SCOF-1, the second is formed from the co-deposition of BDBA and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) to form a dioxaborole-linked SCOF-2 network. The networks were found to produce nanoporous structures of 15 A for SCOF-1 and 29 A for SCOF-2, which agreed with theoretical pore sizes determined from DFT calculations. Both SCOFs were found to have exceptional thermal stability, maintaining their structure until approximately 750 K, which was found to be the polymer degradation temperature from thermal gravimetric analysis (TGA).     

Friction dynamics of confined weakly adhering boundary layers

The nanotribological behavior of self-assembled monolayers is investigated. The latter accommodate friction through transient relaxation and dilatancy effects whose kinetics depends on the structure of the confined layers. Thus, the molecular ordering onto the surfaces controls the level and the stability of the friction coefficient. Moreover, the behavior of these systems is theoretically accounted for using a model based on the kinetics of formation and rupture of adhesive bonds between the two shearing surfaces with an additional viscous term.