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61.
Uwe Karst 《Nachrichten aus der Chemie》2000,48(6):834-835
Unter dem Motto „Science for the 21st Century”︁ fand die 51. Pittsburgh Conference (Pittcon) Mitte März in New Orleans, Louisiana/USA statt. Das Tagungsprogramm mit dem Rekord von fast 1400 Vorträgen und 700 Postern sowie die Messe mit etwa 1200 Ausstellern und 28000 Besuchern waren ein eindrucksvoller Beleg für die thematische Breite und die dynamische Entwicklung der Analytischen Chemie. 相似文献
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Nils Helge Schebb David Falck Helene Faber Eva-Maria Hein Uwe Karst Heiko Hayen 《Journal of chromatography. A》2009,1216(27):5249-5255
A new liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) method for the fast determination of phospholipase A2 (PLA2) activity has been developed. For the first time, the method allows the parallel detection of glycerophosphatidylcholine (GroPCho) as PLA2 substrate as well as of its products fatty acid (FA) and lyso-GroPCho. ESI-MS was carried out in negative ion mode, detecting the FA as [M − H]− ions and the lyso-GroPCho and GroPCho as acetate adducts [M + Ac]−. Utilizing a fast gradient on a short C5-modified silica gel column with 3 μm particles, five GroPChos, five FAs and six lyso-GroPChos could be separated according to their chain length in less than 3 min. A very high average chromatographic efficiency of 41,200 theoretical plates (plate height 0.5 μm) was achieved for the separation of the GroPChos. The method was applied for monitoring the release of arachidonic acid (20:4 FA) and 1-stearoyl-lyso-sn-GroPCho (18:0 GroPCho) from unilamellar vesicles of 1-stearoyl-2-arachidonoyl-sn-GroPCho (18:0/20:4 GroPCho). With a limit of detection of 0.5 pmol (total amount injected on column) for the FAs and lyso-GroPChos and 1.5 pmol for the GroPChos as well as a linear range of 1.5 decades, the method has proven to be suitable for the monitoring of different secretory PLA2 (sPLA2) conversions. Furthermore, it was applied to screen a small library of PLA2 inhibitors for their activity towards sPLA2 type V and snake venom of Bothrops moojeni. In both cases, active samples could be directly identified. With its short analysis time, its high chromatographic efficiency and the parallel detection of substrate and all products, the developed LC–ESI-MS method is well suited for the analysis of PLA2 activity. 相似文献
65.
The metabolism of the selective estrogen receptor modulator toremifene was simulated in an on-line electrochemistry/enzyme
reactor/liquid chromatography/mass spectrometry system. To simulate the oxidative phase I metabolism, toremifene was oxidized
in an electrochemical (EC) flow-through cell at 1,500 mV vs. Pd/H2 to its phase I metabolites, some of which are reactive quinoid species. In the presence of glutathione-S-transferase (GST), these quinoid compounds react with glutathione, which is also the common detoxification mechanism in the
body. While reacting with glutathione, the chlorine atom is eliminated from the toremifene moiety. Due to higher conversion
rates, GST supplied in continuous flow proved to be more efficient than using immobilized GST on magnetic microparticles.
In the absence of GST, not all GSH adducts are formed, proving the necessity of a phase II enzyme to simulate the complete
metabolic pathway of xenobiotics in an on-line EC/LC/MS system.
Figure Mass voltammogram of toremifene 相似文献
66.
A series of proton exchange membranes based on sulfonated polyarylene ether ketones(SPAEKs) was used to study the effect of sulfonation degree on proton conductivity, methanol permeation and performance of direct methanol fuel cells(DMFCs). Dependences of physical characteristics of the membranes, i. e., proton conductivity, water uptake, swelling ratio, methanol permeability and ion exchange capacity(IEC) were systematically studied. Both methanol permeability and proton conductivity of the SPAEK membrane grow rapidly as the increase in sulfonation degree since methanol molecules and protons share the same transfer channel. However,the methanol permeability plays more important role comparing to proton conductivity. As a result, the SPAEK membrane with a medium sulfonation degree(60%) was found to yield the best performance in a DMFC due to the acquirement of balanced conductivity and methanol permeability. 相似文献
67.
Jahn S Lohmann W Bomke S Baumann A Karst U 《Analytical and bioanalytical chemistry》2012,402(1):461-471
In the present study, a method for the analysis of reactive metabolites via liquid chromatography (LC) with inductively coupled
plasma–mass spectrometry (MS) was developed. A ferrocenyl-modified glutathione (GSH) reagent, consisting of GSH and succinimidyl-3-ferrocenylpropionate,
was synthesized. Derivatization of the tripeptide was performed at the N-terminus, leaving the nucleophilic thiol group vacant
for the attack of electrophilic compounds. The potential of ferrocenylpropionate (FP)-GSH as a trapping agent for reactive
metabolites was investigated using an electrochemical flow-through cell for metabolism simulation coupled online to a LC system
with electrospray ionization mass spectrometric detection. The pharmaceuticals amodiaquine, an antimalarial agent, and clozapine,
an antipsychotic compound, served as model substances. By proving the successful adduct formation between the reactive metabolite
and ferrocene-labeled GSH, it could be shown that FP-GSH is an effective trapping agent which eases routine reversed-phase
LC analyses. In contrast to GSH, which is usually used for the conjugation of reactive metabolites and where the resulting
adducts often show no or only very little retention, FP-GSH facilitates the detection of the corresponding metabolite adducts
due to higher retention times. 相似文献
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Composite membranes based on sulfonated silica/sulfonated poly(ether ether ketone)(SPEEK) were prepared by means of sol-gel method so as to gain a high conductivity and reasonable methanol permeability.The sulfonated silica is generated in situ via the hydrolysis of sulfonated 3-anminopropyl triethoxysilane(KH550) synthesized newly from 3-aminopropyl triethoxysilane and 1,4-butane sultone.The membrane with a silica mass fraction of 5% exhibits a conductivity of 0.187 S/cm at 80 °C and a methanol coefficient with 9.72×10-7 cm2/s.The composite membranes show improved condutive ability and better selectivity that can be promisingly used in direct methanol fuel cell. 相似文献
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