Comparison of Resins for Metal Oxide Affinity Chromatography with Mass Spectrometry Detection for the Determination of Phosphopeptides

Protein phosphorylation is a crucial regulatory mechanism in majority of biological processes. During MS, there is a general need to diminish suppression effect of non-phosphorylated peptides and counterbalance low abundance and insufficient ionization of phosphopeptides. Therefore, selective enrichment of their content in complex mixture has become an indispensable part of any phosphoproteomic study. In this work we employed metal oxide affinity chromatography (MOAC) approach. We have compared “classic” approach of mixing TiO₂ and peptides in a microtube with “microcolumns” – commercial tips NuTips (TiO₂/ZrO₂ 1:1) and TopTips® (TiO₂, TiO₂/ZrO₂ 1:1, and ZrO₂). Selectivity of the given media towards phosphopeptides was tested on a tryptic digest of mixture of bovine proteins: α /β-casein and fetuin (phosphoproteins) with myoglobin and bovine serum albumin (non-phosphorylated proteins) in ratio 1:1:5:5 and 1:1:50:50, respectively. After enrichment, the obtained eluates were analyzed by tandem mass spectrometry (MALDI-TOF/TOF) on ABI 4800 in positive reflectron mode. To each media we applied four different protocols with different composition of loading and washing buffers and we compared efficiency of three displacers (1 M lactic acid, 350 mg/ml DHB, and 0.1 M glutamic acid). In our settings, NuTips® proved as the most efficient media for analysis of low complex samples, since they exhibited the highest phosphoselectivity. Surprisingly, the Titansphere 5 µm particles outperformed mixed TopTips, which against our expectations showed the lowest binding selectivity and reproducibility even after addition of three different displacers.     

The catalyzed hydrosilation reaction: substituent effects

Ab initio electronic structure calculations using MP2 wavefunctions have been used to investigate a reaction path for the hydrosilation reaction catalyzed by divalent titanium [modeled by TiH₂, TiCl₂, and Ti(C₅H₅)₂]. Optimized structures and energies are presented. All model reactions predict a barrierless reaction path compared to a barrier of 78 kcal/mol for the uncatalyzed reaction. Received: 11 August 1998 / Accepted: 3 September 1998 / Published online: 23 February 1999     

Cobalt phthalocyanine derivatives supported on TiO2 by sol–gel processing: Part 2. Activity in sulfide and ethanethiol oxidation

The catalytic activity of cobalt(II) 2,9,16,23-tetrasulphophthalocyanine and cobalt(II) 2,9,16,23-tetra(chlorosulphonyl)phthalocyanine covalently bonded to a TiO₂ matrix by sol–gel processing was investigated for sulfide and ethanethiol (CH₃CH₂SH) liquid-phase oxidation. A comparison of the kinetic data as well as the state of active component by using electron spectroscopy in dependence on precursors was carried out. Kinetic data shows that the most stable and active catalysts for ethanethiol oxidation are both CoPc(SO₃H)₄ and CoPc(SO₂Cl)₄ in TiO₂ from Ti(OⁱPr)₄, whereas in the case of Na₂S oxidation in neutral medium the activity of the former is higher.     

Template-based growth of titanium dioxide nanorods by a particulate sol-electrophoretic deposition process

TiO 2 nanorods have been successfully grown into a track-etched polycarbonate (PC) membrane by a particulate sol-electrophoretic deposition from an aqueous medium.The prepared sols had a narrow particle size distribution around 17 nm and excellent stability against aging,with zeta potentials in the range of 47-50 mV at pH 2.It was found that TiO 2 nanorods were grown from dilute aqueous sol with a low,0.1-M concentration.Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that a full conversi...     

Hydrophilicity of amorphous TiO2 ultra-thin films

The UV-light-induced hydrophilicity of amorphous titanium dioxide thin films obtained by radio frequency magnetron sputtering deposition was studied in relation with film thickness. The effect of UV light irradiation on the film hydrophilicity was fast, strong and did not depend on substrate or thickness for films thicker than a threshold value of about 12 nm, while for thinner films it was weak and dependent on substrate or thickness. The weak effect of UV light irradiation observed for the ultra-thin films (with thickness less than 12 nm) is explained based on results of measurements of surface topography, UV-light absorption and photocurrent decay in vacuum. Comparing to thicker films, the ultra-thin films have a smoother surface, which diminish their real surface area and density of defects, absorb partially the incident UV light radiation, and exhibit a longer decay time of the photocurrent in vacuum, which proves a spatial charge separation. All these effects may contribute to a low UV light irradiation effect on the ultra-thin film hydrophilicity.     

工业硅中钛、磷的测定

在pH1的盐酸介质中，Ti（Ⅳ）与变色酸形成桔红色配合物，Fe（Ⅲ）干扰用坏血酸还原消除；在0.42mol/L硫酸介质中，PO4^3-与钼酸铵形成磷钼杂多酸，用抗坏血酸还原为钼蓝，为此对工业硅中钛、磷进行光度法测定，结果令人满意。     

Titanium (IV) as an essential promoter in the asymmetric addition of diethylzinc to aldehydes catalyzed by aminonaphthol and imine ligands based on 3-substituted binaphthol

By using indirect reductive amination and condensation, two types of aminonaphthol and imine ligands based on 3-substituted binaphthol have been synthesized, respectively. When their catalytic effectiveness was tested by the ethylation of aldehydes with diethylzinc, titanium tetraisopropoxide was found essential to get good results with ee up to 90%.     

Ultra-thin film growth of titanium dioxide on W(1 0 0)

We have employed low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy to follow the epitaxial growth of thin films of TiO₂ on W(1 0 0). The films were grown both by metal vapour deposition of titanium onto the substrate in UHV with subsequent annealing in a low partial pressure of oxygen, and by metal vapour deposition in a low partial pressure of oxygen. LEED patterns showed the characteristic patterns of (1 1 0) oriented rutile. A systematic spot splitting was observed and attributed to a stepped surface. The calculated step height was found to be in good agreement with that expected for rutile TiO₂(1 1 0), 3.3 Å. Titanium core level shifts were used to identify oxidation states as a function of film thickness allowing the interpretation in terms of a slightly sub-stoichiometric interface layer in contact with the substrate. In combination with the LEED patterns, the film structure is therefore determined to be (1 1 0) oriented rutile with a comparable level of stoichiometry to UHV prepared bulk crystals. The ordered step structure indicates considerable structural complexity of the surface.     

ICP－AES法同时测定聚酯切片中的钛和铁

本文介绍ＩＣＰ－ＡＥＳ法同时测定聚酯切片中钛和铁的方法。试样以干法分解，以硫酸，硫酸铵溶解残渣后进行测试。回收率为９３．５％－１００．６％，ＲＳＤ＜３．８３％     

Critical evaluation of potentiometric redox titrations in enology

Measurements of the zero current potential of a platinum electrode immersed in solutions of tanins or in wines of various origins, were performed during the additions of a solution of Ti(III), or of a solution of dichlorophenolindophenol (DCPIP), in order to obtain a global indication for the resistance to oxidation of some wines. The steady state intensity-potential curves on a platinum electrode highlight the occurrence of mixed potentials between the oxidation of ethanol or catechin and the reduction of oxygen present at very low concentrations, as well as the irreversibility of the redox system Ti(IV)/Ti(III). The adsorption of various species on the platinum and the slowness of the oxidation reactions by DCPIP exclude use of potentiometric titration theory. The shape of the potential-reagent volume curves depends on the nature of the solution and on the rate of reagent introduction. Generally, due to the slowness of the oxidation reactions with DCPIP it is impossible to find a linear relationship between the volume of titrant solution necessary to reach the inflexion point of the curves and the solution composition.