Capillary isoelectric focusing of proteins utilizing poly(vinylpyrrolidone)- and plexiglas-coated columns

Fused-silica capillaries chemically derivatized with silane/poly(vinylpyrrolidone) (PVP) or dynamically modified with plexiglas [poly(methyl methacrylate)] were prepared and evaluated with regard to column stability and separation performance for capillary isoelectric focusing of standard proteins. The PVP coating showed the better stability and was good for at least 100 runs while the plexiglas coating started to deteriorate after about 30 runs. The time spent for the plexiglas coating is about 40 minutes while the PVP coating requires two days. The migration time reproducibility was better with the PVP capillary (RSD 0.7-1.6%, n = 5) compared to the plexiglas-coated column (RSD 1.2-2.9%, n = 5) while peak area and height varied over a similar interval (RSD 2-28.1% area; 0.9-22.7% height, n = 5). The two most consistent proteins in this evaluation, viz. myoglobin A and carbonic anhydrase II, showed linear dynamic ranges between 5-150 and 5-50 microg/mL, and limits of detections at 2 and 1 microg/mL, respectively, employing UV detection at 280 nm.     

Effect of adsorbed water on the activity of MoO3 catalysts in the double bond isomerization of olefins

Adsorbed water on molybdena catalysts calcined at different temperatures, may both increase or decrease the catalytic activity, depending upon the mode of adsorption and the number of adsorbed molecules. Our results prove that Brönsted acidic hydroxy groups are principal parts of the active sites, and Lewis acidic and/or basic centers are also required for catalytic activity in the double bond isomerization of olefins.

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Semiautomatic and automatic catalytic amperometric and catalytic constant-current potentiometric titrations of gold(III)

Semiautomatic and automatic amperometry and constant-current potentiometry were used to follow the course of catalytic titration of gold(III) with potassium iodide. The Ce(IV)-As(III) system in the presence of sulfuric acid was used as the indicator reaction. The possibilities of the application of two types of graphite electrodes were investigated. The effect of concentration of the indicator reaction components, and the presence of organic solvents and acids on the shape of the catalytic titration curves was studied. Amounts of 80–900 μg of gold(III) were determined with a relative standard deviation less than 1.1%. The results obtained are in good agreement with those of comparable methods.     

Effects of different alkali metal ions on the cationization of poly(ethylene glycol)s in matrix-assisted laser desorption/ionization mass spectrometry: a new selectivity parameter

The cationization of poly(ethylene glycol)s, PEG 4000 and PEG 6000, under matrix-assisted laser desorption/ionization conditions was studied by using different concentration ratios of the sodium ion, as the reference ion, and another alkali metal ion (Li(+), K(+), Rb(+), Cs(+)). A linear correlation was found between the intensity ratio of the sodiated PEGs and PEGs cationized with alkali metal ions versus the initial concentration ratio of sodium and alkali metal ions. The slopes of these straight lines are proposed as a novel selectivity ratio for the ionization process. The intensity distribution of the cationized PEGs was also investigated. It was found that the cationized oligomers follow Poisson statistics. The M(n) and M(w) values were also evaluated. An explanation for the observed effects is given.     

Can a rate constant independent of sample size be obtained from the rate equation generally used in thermal analysis?

Some consequences of using the rate equation d/dt=k _t f() are shown on a simple example. It is demonstrated thatk _t usually depends on the sample size, and that it is usually incorrect to assume that if mass and heat transport effects are avoided both and d/dt — as functions of time — are independent of the initial mass. Rate equations should be based on real local quantities.     

Phospholes with Reduced Pyramidal Character from Steric Crowding. 2. Photoelectron Spectral Evidence for Some Electron Delocalization in 1-(2,4-Di-tert-butyl-6-methylphenyl)-3-methylphosphole

Photoelectron spectroscopy has been explored as a tool to measure the flattening of the phosphorus pyramid in a phosphole as caused by a large, sterically demanding P-substituent. Earlier PE spectra had shown no difference in ionization energies (IE) for simple phospholes and their tetrahydro derivatives (both around 8.0-8.45 eV). Calculations of the Koopmans IE at the Hartree-Fock 6-31G level for 1-methylphospholane showed that, as is known for nitrogen, planarization at phosphorus markedly reduced the ionization energy value (8.74 to 6.29 eV). A reduction in IE also occurred on planarizing 1-methylphosphole, but to a lesser extent, being offset by increased electron delocalization (8.93 to 7.16 eV). This suggests that experimental comparison of IE for the unsaturated and saturated systems could be used to detect the presence of electron delocalization in the former. The IE experimentally determined for the crowded 1-(2,4-di-tert-butyl-6-methylphenyl)-3-methylphosphole was 7.9 eV, the lowest ever recorded for a phosphole. The corresponding phospholane had IE 7.55 eV. The difference in the values is attributed to electron delocalization in the phosphole. Calculations performed on the related model 1-(2-tert-butyl-4,6-dimethylphenyl)phosphole showed that the P-substituent adopted an angle of 55.7 degrees (DFT/6-31G level; 57.6 degrees at the HF/6-31 level) with respect to the C(2)-P-C(5) plane (for P-phenyl, 67.1 degrees and 68.3 degrees, respectively).     

Monitoring of optical isomers of chiral alcohols and derivatives by chiral gas chromatography. Effect of derivatization on the enantio-differentiation

Summary Gas chromatographic chiral separation of several chiral 2-and 3-alkanols and diols was studied both in their free hydroxyl and in their trimethylsilyl ether forms. First, the derivatization procedure was verified through the identification of the trimethylsilyl ethers formed on the basis of their mass spectra and optimized to obtain quantitative reaction. The optimized procedure was applied to the trimethylsilylation of racemic mixtures of various hydroxyl compounds. The silylation was found to be highly effective in the improvement of the separation of the individual enantiomers. The major advantages of the derivatization process can be summarized as: (i) excellent baseline separation of the enantiomers of the silyl ethers was achieved in contrast to the parent OH-containing compounds, (ii) the sensitivity of detection highly increased, (iii) the separations do not show any significant concentration dependence and finally (iv) the analysis time needed decreased significantly. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Kinetics and mechanism of the reaction of tetracobalt dodecacarbonyl with carbon monoxide under pressure

The kinetics of the reaction of tetracobalt dodecacarbonyl with carbon monoxide to form dicobalt octacarbonyl in n-hexane have been investigated over a wide range of temperature and CO pressure. The reaction is first order in [Co₄(CO)₁₂]; the order in [CO] changes between one (at low pressures and high temperatures) and two (at high pressures and low temperatures).Activation parameters have been estimated and a mechanism involving initial reversible breaking of one CoCo bond, followed by irreversible breaking of a second, is proposed. The first step involves concerted addition of CO while the second can proceed with or without such addition.     

Some regularity properties of algorithms and additive functions with respect to them

Summary The paper deals with the behaviour of the so-called algorithms with respect to interval filling sequences A connection is established between the uniquely representable points and the continuity points of the algorithms; also strong continuity properties on monotonic algorithms are proved. Finally the results are applied to additive functions. The theorems extend some former results by the authors, by I. Kátai and by A. Járai.Dedicated to the memory of Alexander M. Ostrowski on the occasion of the 100th anniversary of his birth     

On the maximal number of certain subgraphs inK r -free graphs

Given two graphsH andG, letH(G) denote the number of subgraphs ofG isomorphic toH. We prove that ifH is a bipartite graph with a one-factor, then for every triangle-free graphG withn verticesH(G) H(T ₂(n)), whereT ₂(n) denotes the complete bipartite graph ofn vertices whose colour classes are as equal as possible. We also prove that ifK is a completet-partite graph ofm vertices,r > t, n max(m, r – 1), then there exists a complete (r – 1)-partite graphG* withn vertices such thatK(G) K(G*) holds for everyK _r -free graphG withn vertices. In particular, in the class of allK _r -free graphs withn vertices the complete balanced (r – 1)-partite graphT _r–1(n) has the largest number of subgraphs isomorphic toK _t (t < r),C ₄,K _2,3. These generalize some theorems of Turán, Erdös and Sauer.Dedicated to Paul Turán on his 80th Birthday