Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

Multiple glass-transition temperatures in thin supported films of isotactic PMMA as revealed by enhanced Raman scattering

The glass-transition temperature, Tg, of isotactic PMMA thin films has been measured for four thicknesses by enhanced Raman spectroscopy and ellipsometry. This was made possible by inserting a silica spacer layer between the film and the substrate. The use of such a spacer drastically improves the sensitivity of Raman scattering measurements. The improvement in the sensitivity allows us to study phenomena involving changes in molecular dynamics, such as the phase transition, and to probe the existence in very thin films of several thickness-dependent transition temperatures, Tg(h). This in turn is interpreted as the occurrence in the film of a layered structure. The influence of the polymer concentration on the conformation of the surface adsorbed polymer layer and therefore on Tg(h) is discussed.     

First syntheses of model long-chain trichloro[ω-(trimethylsilyl)alkynyl]silanes suitable for self-assembled monolayers on silicon surfaces

The preparation of the title compounds involves the introduction of the required Me₃SiCC and trichlorosilyl groups at the termini of the alkyl chain via derivatization of easily accessible and inexpensive materials/reagents. Trichloro[ω-(trimethylsilyl)alkynyl]silanes are useful for the linkage to a hydroxylated silicon surface for multilayer formation and for further chemical modification of the tail group of the monolayer.     

Immunization with genetically attenuated P52-deficient Plasmodium berghei sporozoites induces a long-lasting effector memory CD8+ T cell response in the liver

Background

The induction of sterile immunity and long lasting protection against malaria has been effectively achieved by immunization with sporozoites attenuated by gamma-irradiation or through deletion of genes. For mice immunized with radiation attenuated sporozoites (RAS) it has been shown that intrahepatic effector memory CD8⁺ T cells are critical for protection. Recent studies have shown that immunization with genetically attenuated parasites (GAP) in mice is also conferred by liver effector memory CD8⁺ T cells.

Findings

In this study we analysed effector memory cell responses after immunization of GAP that lack the P52 protein. We demonstrate that immunization with p52 ^-GAP sporozoites also results in a strong increase of effector memory CD8⁺ T cells, even 6 months after immunization, whereas no specific CD4⁺ effector T cells response could be detected. In addition, we show that the increase of effector memory CD8⁺ T cells is specific for the liver and not for the spleen or lymph nodes.

Conclusions

These results indicate that immunization of mice with P. berghei p52 ^-GAP results in immune responses that are comparable to those induced by RAS or GAP lacking expression of UIS3 or UIS4, with an important role implicated for intrahepatic effector memory CD8⁺ T cells. The knowledge of the mediators of protective immunity after immunization with different GAP is important for the further development of vaccines consisting of genetically attenuated sporozoites.     

Search for a fourth-generation quark more massive than the Z0 boson in p&pmacr; collisions at radicals = 1.8 TeV

We present the results of a search for pair production of a fourth-generation charge -1 / 3 quark (b(')) in sqrt[s] = 1.8 TeV p&pmacr; collisions using 88 pb(-1) of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process b(')-->bZ(0) and that the b(') mass is greater than m(Z)+m(b). We studied the decay mode b(')b(');-->Z(0)Z(0)b&bmacr; where one Z0 decays into e(+)e(-) or &mgr;(+)&mgr;(-) and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the sigma(p&pmacr;-->b(')b(');)x[B(b(')-->bZ(0))](2) is established as a function of the b(') mass. We exclude at 95% confidence level a b(') quark with mass between 100 and 199 GeV/c(2) for B(b(')-->bZ(0)) = 100%.