A new type of mixed framework in the crystal structure of binary molybdate Nd2Zr3(MoO4)9

Single crystals of binary molybdate Nd₂ZrMoO₄)₉ were grown. The crystal structure of this compound was investigated by X-ray diffraction analysis (CAD-4 diffractometer, MoKα radiation, 2844 reflections. R = 0.0230), and a new type of structure was found. The crystals are trigonal with cell dimensions a = 9.804(1), c = 58.467(12) å, V= 4867(1) å³, Z = 6, d_calc = 4.098 g/cm₃, space group R ₃ ^? c. The structure involves polyhedra of three types: MoO₄ tetrahedra, ZrO₆ octahedra, and NdO₉ tricapped trigonal prisms linked by their common vertices into an original three-dimensional framework.     

In Situ Formation of Gold Nanoparticles within a Polymer Particle and Their Catalytic Activities in Various Chemical Reactions

Composite materials consisting of nanoscale gold particles and protective polymer shells were designed and tested as catalysts in various chemical reactions. Initially, the systematic incorporation of multiple gold nanoparticles into a poly(N-isopropylacrylamide) particle was achieved by an in situ method under light irradiation. The degree of gold nanoparticle loading, along with the structural and morphological properties, was examined as a function of the amount of initial gold ions and reducing agent. As these gold nanoparticles were physically-embedded within the polymer particle in the absence of strong interfacial interactions between the gold nanoparticles and polymer matrix, the readily-accessible surface of the gold nanoparticles with a highly increased stability allowed for their use as recyclable catalysts in oxidation, reduction, and coupling reactions. Overall, the ability to integrate catalytically-active metal nanoparticles within polymer particles in situ allows for designing novel composite materials for multi-purpose catalytic systems.     

Phase equilibria in the systems Rb2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Al, In, Sc, Fe(III)) and the crystal structure of double molybdate RbFe(MoO4)2

The systems Rb₂MoO₄-R₂(MoO₄)₃-Hf(MoO₄)₂ have been investigated in the subsolidus region by X-ray powder diffraction, DTA, and IR spectroscopy. Triple molybdates of the composition 5: 1: 2 are formed in the systems with R = Al, In, Sc, and Fe. Molybdates of composition 5: 1: 3 and 1: 1: 1 are found in the iron(III)-containing system in addition to the 5: 1: 2 molybdate. Single crystals of the double molybdate RbFe(MoO₄)₂, which is formed in the Rb₂MoO₄-Fe₂(MoO₄)₃ system, have been grown. The structure of this double molybdate has been refined using X-ray diffraction data (X8 APEX automated diffractometer, MoK _α radiation, 373 F(hkl), R = 0.0287). The trigonal unit cell parameters are the following: a = b = 5.6655(2) Å, c = 7.5061(4) Å, V = 208.65(1) ų, Z = 1, ρ_calc = 3.670 g/cm³, space group R3m1. The structure is formed by layers of FeO₆ octahedra sharing corners with MoO₄ tetrahedra and RbO₁₂ icosahedra.     

Absolute quantitation of host cell proteins in recombinant human monoclonal antibodies with an automated CZE‐ESI‐MS/MS system

We report the first use of CZE for absolute characterization of host cell proteins (HCPs) in recombinant human monoclonal antibodies. An electrokinetically pumped nanoelectrospray interface was used to couple CZE with a tandem mass spectrometer. Three isotopic‐labeled peptides (LSFDKDAMVAR, VDIVENQAMDTR, and LVSDEMVVELIEK) were synthesized by direct incorporation of an isotope‐labeled lysine or arginine. The heavy‐labeled peptides were spiked in the HCP digests at known concentrations. After CZE‐ESI‐MS/MS analysis, the peaks of native and isotopic‐labeled peptides were extracted with mass tolerance ≤ 5 ppm from the electropherograms, and the ratios of peak area between native and isotopic‐labeled peptides pairs were calculated. Calibration curves (the ratios of peak area versus spiked peptide amount) with R² values of 0.999, 0.997, and 0.999 were obtained for the three HCP peptides, and the absolute amounts of the three proteins present were determined to be at the picomole level in a 20 μg sample of digested HCPs. The target proteins were present at the 7–30 ppt level in the purified HCP samples.     

Double molybdate Tl2Mg4(MoO4)3: Synthesis, structure, and properties

Single crystals of molybdate Tl₂Mg₂(MoO₄)₃ are grown, and its crystal structure is refined in an X-ray diffraction experiment (an automated diffractometer, MoK _α radiation, 914 F(hkl) reflections, R = 0.0459). The crystal are cubic with a = b = c = 10.700(1) Å, V = 1225.0(2) ų, Z = 4, space group P2₁3. The mixed 3D framework of the structure is built of MoO₄ tetrahedra and two types of corner-sharing MgO₆ octahedra. Two types of thallium atoms occupy large interstices.     

Synthesis and X‐Ray Study of Single Crystals of K5(Cd0.5Zr1.5)(MoO4)6 Triple Molybdate

Single crystals of K₅(Cd_0.5Zr_1.5)₂(MoO₄)₆ molybdate have been grown. Its composition and crystal structure have been established from Xray diffraction data CAD4 automatic diffractometer, MoK radiation, 940 F(hkl), R = 0.0234. The crystals have a trigonal unit cell a = b = 10.624(1), c = 37.694(6), V = 3684.5(8)³, and space group R3c. The 3D mixed framework of the molybdate structure is formed by two kinds of Mo tetrahedra and (Cd, Zr) octahedra joined by shared O vertices. The large cavities in the framework are occupied by K atoms of three kinds. The distribution of Cd²⁺ and Zr⁴⁺ cations over two crystallographic positions has been refined.     

Phase formation in the Dy2O3-HfO2-MoO3 system. Crystal structure of the new binary molybdate Dy2Hf2(MoO4)7

Phase relations have been studied for the subsolidus region of the Dy₂O₃-HfO₂-MoO₃ system; binary molybdates, Dy₂Hf(MoO₄)₅ and Dy₂Hf₂(MoO₄)₇, were found to form. The crystal structure of the latter has been solved (a = 20.661(3) , b = 9.816(1) , c = 13.796(3) , = 113.47(1)°, Z = 4, space group C2/c, R = 0.023) and found to be a new type of structure. In the structure, MoO₄ tetrahedra are linked by their vertices with HfO₆ octahedra and DyO₈ tetragonal antiprisms to form a 3D open-work, in which one can isolate double-row tetrahedral and octahedral chains extended down the c axis.Original Russian Text Copyright © 2004 by S. F. Solodovnikov, B. G. Bazarov, E. Yu. Badmaeva, Yu. L. Tushinova, E. S. Zolotova, and Zh. G. BazarovaTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 692–697, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Comparing normal modes across different models and scales: Hessian reduction versus coarse‐graining

Dimension reduction is often necessary when attempting to reach longer length and time scales in molecular simulations. It is realized by constraining degrees of freedom or by coarse‐graining the system. When evaluating the accuracy of a dimensional reduction, there is a practical challenge: the models yield vectors with different lengths, making a comparison by calculating their dot product impossible. This article investigates mapping procedures for normal mode analysis. We first review a horizontal mapping procedure for the reduced Hessian techniques, which projects out degrees of freedom. We then design a vertical mapping procedure for the “implosion” of the all‐atom (AA) Hessian to a coarse‐grained scale that is based upon vibrational subsystem analysis. This latter method derives both effective force constants and an effective kinetic tensor. Next, a series of metrics is presented for comparison across different scales, where special attention is given to proper mass‐weighting. The dimension‐dependent metrics, which require prior mapping for proper evaluation, are frequencies, overlap of normal mode vectors, probability similarity, Hessian similarity, collectivity of modes, and thermal fluctuations. The dimension‐independent metrics are shape derivatives, elastic modulus, vibrational free energy differences, heat capacity, and projection on a predefined basis set. The power of these metrics to distinguish between reasonable and unreasonable models is tested on a toy alpha helix system and a globular protein; both are represented at several scales: the AA scale, a Gō‐like model, a canonical elastic network model, and a network model with intentionally unphysical force constants. Published 2012 Wiley Periodicals, Inc.     

Focusing of explosion waves: Three-dimensional mathematical modeling

The propagation and focusing explosionlike waves in a cubic volume filled with a gas was considered. The wave is generated by the expansion of a small volume of a gas with enhanced parameters located at different points inside the cube. This formulation of the problem simulates the process initiated by an explosion in a volume filled with a gas and the character of loading on the walls of the volume. 3D calculations of the propagation and cumulation of explosion waves with a short positive phase were performed for the first time. The results can be used in analyzing experiments aimed at modeling the initiation of combustion by the waves generated by a primary source in closed volumes with complex geometry.     

The jet at the switch-on stage in a numerical and physical experiment

We analyze the possibility of predicting the structure of the jet at the formative stage using a comparison of experimental results and compulations carried out for flows beyond an acoustic nozzle. The correspondence of the computational model to the conditions in which the experiments were performed is discussed. It is shown that the question of the degree of reliability of the computational prediction should be decided on the basis of comparison of the approximation relations that describe the experimental and computational data. Translated fromProblemy Matematicheskoi Fiziki, 1998, pp. 162–171.