Effect of impurities on the matrix-assisted laser desorption/ionization mass spectra of insulin.

The effect of impurity (sodium sulfate Na2SO4; copper sulfate CuSO4; potassium ferrocyanide K4Fe(CN)6; and triammonium citrate (NH4)3C6H5O7) concentration on the positive matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectra of insulin is described. 2,5-Dihydroxybenzoic acid was used as a desorption matrix. The estimated maximum concentrations of tested salts for which no insulin signal was observed were determined.     

1H, 13C, 15N and 195Pt NMR studies of Au(III) and Pt(II) chloride organometallics with 2‐phenylpyridine

¹H, ¹³C, ¹⁵N and ¹⁹⁵Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2′)‐chelated, deprotonated 2‐phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl₂], trans(N,N)‐[Pt(2ppy*)(2ppy)Cl] and trans(S,N)‐[Pt(2ppy*)(DMSO‐d₆)Cl] (formed in situ upon dissolving [Pt(2ppy*)(µ‐Cl)]₂ in DMSO‐d₆) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective ¹H, ¹³C and ¹⁵N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Δ^1H_coord = δ^1H_complex ? δ^1H_ligand, Δ^13C_coord = δ^13C_complex ? δ^13C_ligand, Δ^15N_coord = δ^15N_complex ? δ^15N_ligand), as well as ¹⁹⁵Pt chemical shifts and ¹H‐¹⁹⁵Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen‐adjacent H(6) protons and metallated C(2′) atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

Evolution Hemivariational Inequality with Hysteresis Operator in Higher Order Term

The authors study evolution hemivariational inequalities of semilinear type containing a hysteresis operator. For such problems we establish an existence result by reducing the order of the equation and then by the use of the time-discretization procedure.     

Hydrothermal synthesis of precursors of neodymium oxide nanoparticles

The nanometric precursors of neodymium oxide of various morphologies were prepared via a hydrothermal reaction route. The precursors and their thermal evolution to neodymium oxide phase were characterised by means of X-ray diffraction (XRD), transmission electron microscopy (TEM, HRTEM), thermal analysis (TG, DTA, EGA-MS), FTIR and atomic force microscopy (AFM). It was found that the reaction conditions (temperature, pressure) played a key role for the product formation of desired morphology and structure. At mild conditions (140 °C) precursor with unusual fibrous morphology and Nd(OH)_2.45(Ac)_0.550.45H₂O stoichiometry was obtained. Upon heating this phase transformed, via intermediate cubic oxide, into trigonal Nd₂O₃ at 800 °C. Nd(OH)₃ hydroxide obtained at severe conditions (180 °C) transformed upon heating into cubic Nd₂O₃ phase at about 500 °C and this phase was stabilised even at 800 °C. The fibrous precursors appeared to be a convenient material for preparation of homogeneous thin coatings on planar substrates is shown.     

The mass spectra of some 2- and 4-pyridylethylamines

The mass spectra of some N,N-disubstituted 2-aminoethylpyridines are reported and their principle fragmentation routes analysed.     

Capillary electrophoresis as a tool for a cost‐effective assessment of the activity of plant membrane enzyme chlorophyllase

The potential of the CE‐based enzymatic assay has been demonstrated in case of a typical plant membrane enzyme – chlorophyllase. An efficient, automated and rapid semi‐quantitative method has been developed, which allowed us to assess the activity of the enzyme via two strategies. Firstly, a reaction conducted in a vial placed directly on the sample tray was combined with the concomitant separation and detection of reagents. The method was used to monitor the reaction progress. Secondly, an online approach was applied using an electrophoretically mediated mixing. The reaction was performed in?capillary, resulting in an extreme reduction of the reagent amounts required for a single run. Both methods were effective in the assessment of the activity of a membrane enzyme, a member of protein class known to pose experimental difficulties.     

Experimental and quantum-chemical studies of 15N NMR coordination shifts in palladium and platinum chloride complexes with pyridine, 2,2'-bipyridine and 1,10-phenanthroline

A series of Pd and Pt chloride complexes with pyridine (py), 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen), of general formulae trans-/cis-[M(py)2Cl2], [M(py)4]Cl2, trans-/cis-[M(py)2Cl4], [M(bpy)Cl2], [M(bpy)Cl4], [M(phen)Cl2], [M(phen)Cl4], where M = Pd, Pt, was studied by 1H, 195Pt, and 15N NMR. The 90-140 ppm low-frequency 15N coordination shifts are discussed in terms of such structural features of the complexes as the type of platinide metal, oxidation state, coordination sphere geometry and the type of ligand. The results of quantum-chemical NMR calculations were compared with the experimental 15N coordination shifts, well reproducing their magnitude and correlation with the molecular structure.     

Interaction of hydrogen with unsupported and supported nickel

The adsorption of molecular hydrogen on Ni powder and on Ni/Al(2)O(3) and Ni/SiO(2) catalysts was studied by the temperature-programmed desorption (TPD) method. The examinations were performed in the flow system, starting the TP measurements at low temperatures of 100 or 78 K, which resulted in the formation of complete characteristics of the interaction of hydrogen with nickel. Generally, three forms of chemisorbed hydrogen were distinguished: alpha, adsorbed on Ni surface, beta, adsorbed in the "second layer", and gamma, located in the subsurface region of nickel. The comparison of the results of this work with those obtained in vacuum systems for various Ni surfaces has led to the conclusion that the same form of hydrogen desorbs from nickel above 200 K in vacuum systems but above 300 K in flow systems. The examinations performed for Ni/Al(2)O(3) and Ni/SiO(2) samples show that alumina suppresses but silica enhances the formation of the beta-form of hydrogen.