Isolation and characterization of modified species of a mutated (Cys125 -Ala) recombinant human interleukin-2

An approach for simultaneous determination of the main type A-trichothecenes by liquid chromatography and atmospheric pressure chemical ionization mass spectrometry is described. Parameters for coupling of LC-MS such as cone voltage, nebulizing temperature and the LC flow-rate, were optimized to provide detection of mycotoxins with maximum sensitivity. Furthermore, the effects of cone voltage and temperature on the fragmentation pattern of the tested toxins were studied. Main type A-trichothecenes such as T-2 Toxin, HT-2 Toxin, acetyl T-2 Toxin, diacetoxyscirpenol, monoacetoxyscirpenol (15-acetoxyscirpenol) and neosolaniol were separated on a reversed-phase narrow bore C18 column, using a linear gradient and a flow-rate of 0.3 ml/min. Mass spectra were obtained in positive ion mode for confirmation and quantitation. The method involves extraction and purification of toxins by using multifunctional Mycosep columns. Deuterated T-2 Toxin was used as an internal standard. A linear working range between 80 and 500 microg/kg in matrix with an acceptable correlation coefficient was observed. The developed method was validated by using a blank oats sample. The detection limit in the matrix was found to be between 50 and 85 microg/kg in selected ion mode for all tested A-trichothecenes. Recovery data were found to be between 77 and 101%. Within run and day-to-day precision were determined as having comparable levels to those found using GC methods. Furthermore, the matrix effect was investigated by comparing the internal standard versus the external standard method in quantification studies. In addition, the developed method was applied for the analysis of naturally contaminated oats, maize, barley and wheat samples.     

Elastoplastic strain distribution around an oblique aperture in plates

Six steel plates containing an oblique hole with different inclination angles have been tested. The elastic-plastic response of these plates shows that high plastic strains occur inside the hole on the plane of symmetry. The maximum strain-concentration factor varies with the angle of obliquity of the hole generator and thickness-to-diameter ratio. The location of the maximum strain shifts inwards as the plastic deformation takes place. The results show that at a relatively low nominal-to-yield stress ratio, rather high plastic strains occur near the acute-angle side. In a certain case, the rate of increase of strain is such that unconstrained plastic flow takes place, causing large plastic deformations.     

Determination of carbon, hydrogen and nitrogen in inorganic compounds by means of an automatic organic elemental microanalyzer

The Hewlett Packard Model 185 CHN Analyzer, which is based on an automated modified Dumas combustion technique and was designed for the analysis of organic materials, has been applied to the determination of carbon, nitrogen and hydrogen in inorganic compounds.With minor modifications to the procedure routinely used for the organic analysis, the instrument has proved to be able to broaden its original application field giving in general good performances in the inorganic domain.A particular emphasis has been put in testing nitrates, carbonates, ammonium salts and different kinds of carbon. Till now it appears that the only materials really difficult to analyze are the refractory nitrides, carbides and carbonitrides.Finally some considerations have been made in respect of the determination of the percent weight composition of mixtures through their carbon, nitrogen and hydrogen content.     

An oscillating C2(2-) unit inside a copper rectangle

[Cu4(mu-dppm)4(mu4-eta1,eta2-C[triple bond]C-)]2+ has been shown by 31P and 1H NMR studies to undergo two fluxional processes in solution, the oscillation of the C[triple bond]C2- unit inside the copper rectangle and the flipping of the diphosphines, and this has been supported by DFT(B3LYP) calculations.     

Existence of a Lie bialgebra structure on every Lie algebra

We prove that every non-Abelian, finite-dimensional Lie algebra admits an exact bialgebra structure.     

Building Blocks for the Synthesis of Maytansinoids. Preliminary Communication

The dienal 14 and the ketone 19 , both potential building blocks of maytansinoids, were synthesized starting from ethyl vanillate ( 2 ) via the aldehyde 9 . It could be shown in a preliminary experiment that the dienal 14 can be coupled with 2-lithio-1,3-dithiane to afford compound 16 which exhibits the correctly substituted aromatic part of maytansine as well as its C(9) to C(15) moiety.     

Conformational analysis of flavonoids: Crystal and molecular structure of 3′,5′-dibromo-3-methyl-6,4′-dihydroxyflavone (1:2) triphenylphosphine oxide complex

Crystal structure determination and AM1 molecular orbital calculations were performed on the flavone, 3,5 — dibromo — 3 — methyl — 6,4 — dihydroxyflavone (EMD21388), crystallized as a (1:2) triphenylphosphine oxide (TPPO) co-crystal complex. This is also the first structural report of a 21 TPPO co-crystal complex with a flavone. The calculated molecular structure is in good agreement with the observed crystallographic conformation which shows that the angle between the benzopyrone and phenyl rings,, [C(3)-C(2)-C(1)-C(6)] is 49.1(8)°, compared with the geometry-optimized minimum energy angle of 46.0°. The barrier to rotation in this system is about 3.5 kcal/mol. Biochemical data for EMD 21388 show it is the most potent inhibitor of the enzyme iodothyronine deiodinase and is the strongest competitor for the binding of thyroxine to its serum transport protein transthyretin. This analysis reveals that the flavone can adopt a conformation that has structural homology with the thyroid hormone.     

Synthesis, characterization and photochromic studies of spirooxazine-containing 2,2'-bipyridine ligands and their rhenium(I) tricarbonyl complexes

A series of spirooxazine-containing 2,2'-bipyridine ligands and their rhenium(i) tricarbonyl complexes has been designed and synthesized, and their photophysical, photochromic and electrochemical properties have been studied. The X-ray crystal structures of two of the complexes have been determined. Detailed studies showed that the emission properties of the complexes could readily be switched through photochromic reactions.     

Designing protein dimerizers: the importance of ligand conformational equilibria

In an effort to elucidate the role of ligand conformation in induced protein dimerization, we synthesized a flexible methotrexate (MTX) dimer, demonstrated its ability to selectively dimerize Escherichia coli dihydrofolate reductase (DHFR), and evaluated the factors regulating its ability to induce cooperative dimerization. Despite known entropic barriers, bis-MTX proved to possess substantial conformational stability in aqueous solution (-3.8 kcal/mol >/= DeltaG(fold) >/= -4.9 kcal/mol), exerting a dominant influence on the thermodynamics of dimerization. To dimerize DHFR, bis-MTX must shift from a folded to an extended conformation. From this conclusion, the strength of favorable protein-protein interactions in bis-MTX-E. coli DHFR dimers (-3.1 kcal/mol >/= DeltaG(c) >/= -4.2 kcal/mol), and the selectivity of dimerization for E. coli DHFR relative to mouse DHFR (>10(7)) could be determined. The crystal structure of bis-MTX in complex with E. coli DHFR confirms the feasibility of a close-packed dimerization interface and suggests a possible solution conformation for the induced protein dimers. Consequently, the secondary structure of this minimal foldamer regulates its ability to dimerize dihydrofolate reductase in solution, providing insight into the complex energy landscape of induced dimerization.