Karel Lemr

Palacký University Olomouc

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Vladimı́r Havlı́ček

Czech Academy of Sciences, Institute of Microbiology

Petr Bednář

Palacký University Olomouc

Petr Barták

Palacký University Olomouc

Petr Fryčák

Palacký University Olomouc

JŠ

Juraj Ševčı́k

Palacký University Olomouc

Barbora Papoušková

Palacký University Olomouc

Tomáš Pluháček

Palacký University Olomouc

Kevin A. Schug

The University of Texas at Arlington

Jan Hlaváč

Palacký University Olomouc

Volodymyr Pauk

Palacký University Olomouc

Cooperative Institutions

Palacký University Olomouc

181

Charles University

Czech Academy of Sciences

Regional Centre of Advanced Technologies and Materials

Czech Academy of Sciences, Institute of Microbiology

University Hospital Olomouc

Masaryk University

Institute of Molecular and Translational Medicine

Czech Academy of Sciences, Institute of Experimental Botany

Centre National de la Recherche Scientifique

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Application of Silicon Nanowires and Indium Tin Oxide Surfaces in Desorption Electrospray Ionization

European Journal of Mass Spectrometry (2008)

Jaroslav Pól Petr Novák Michael Volný Gary Kruppa Risto Kostiainen

Two nanostructured surfaces are introduced as advantageous substrates for desorption electrospray ionization mass spectrometry (DESI-MS). Nano-assisted laser desorption/ionization (NALDI) plates coated with silicon nanowires (SiNWs) and indium tin oxide (ITO) layers on glass are both conductive non-polar surfaces that were originally designed as superior substrates for matrix-free laser desorption ionization. In this study, NALDI/SiNWs and ITO were tested as potentially useful DESI substrates for selected model analytes (cyclosporine, beauverolide, surfactin and nystatin). Both nanostructured surfaces produced more intense and longer-lasting signals than other tested surfaces (polytetrafluoroethylene, glass, polymethylmethacrylate and chromatography paper).

Indium tin oxide

Silicon oxide

10.1255/ejms.961

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Citations (16)

Purification and Characterization of Methylamine Oxidase Induced inAspergillus nigerAKU 3302

Bioscience Biotechnology and Biochemistry (1999)

Ivo Frébort Kazunobu Matsushita Hirohide Toyama Karel Lemr Mamoru Yamada

Crude extract of Aspergillus niger AKU 3302 mycelia incubated with methylamine showed a single amine oxidase activity band in a developed polyacrylamide gel that weakly cross-reacted with the antibody against a copper/topa quinone-containing amine oxidase (AO-II) from the same strain induced by n-butylamine. Since the organism cannot grow on methylamine and the already known quinoprotein amine oxidases of the organism cannot catalyze oxidation of methylamine, the organism was forced to produce another enzyme that could oxidize methylamine when the mycelia were incubated with methylamine. The enzyme was separated and purified from the already known two quinoprotein amine oxidases formed in the same mycelia. The purified enzyme showed a sharp symmetric sedimentation peak in analytical ultracentrifugation showing S20,w0 of 6.5s. The molecular mass of 133 kDa estimated by gel chromatography and 66.6 kDa found by SDS-PAGE confirmed the dimeric structure of the enzyme. The purified enzyme was pink in color with an absorption maximum at 494 nm. The enzyme readily oxidized methylamine, n-hexylamine, and n-butylamine, but not benzylamine, histamine, or tyramine, favorite substrates for the already known two quinoprotein amine oxidases. Inactivation by carbonyl reagents and copper chelators suggested the presence of a copper/topa quinone cofactor. Spectrophotometric titration by p-nitrophenylhydrazine showed one reactive carbonyl group per subunit and redox-cyclic quinone staining confirmed the presence of a quinone cofactor. pH-dependent shift of the absorption spectrum of the enzyme-p-nitrophenylhydrazone (469 nm at neutral to 577 nm at alkaline pH) supported the identity of the cofactor with topaquinone. Nothern blot analysis indicated that the methylamine oxidase encoding gene is largely different from the already known amine oxidase in the organism.

Amine oxidase (copper-containing)

Galactose oxidase

Tyramine

10.1271/bbb.63.125

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Citations (15)

Metabolism of olomoucine, roscovitine, and bohemine in small laboratory rodents

Cellular & Molecular Biology Letters (1998)

Z Chmela Jozef Veselý Karel Lemr Jan Hanuš Libor Havlı́ček

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Citations (1)

Liquid chromatographic separation of pregabalin and its possible impurities with fluorescence detection after postcolumn derivatization with o-phtaldialdehyde

Journal of Pharmaceutical and Biomedical Analysis (2010)

Michal Douša Petr Gibala Karel Lemr

Excitation wavelength

10.1016/j.jpba.2010.04.008

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Citations (36)

Scanning electron microscopic imaging of surface effects in desorption and nano‐desorption electrospray ionization

Journal of Mass Spectrometry (2011)

Filip Kaftan Olga Kofroňová Oldřích Benada Karel Lemr Vladimı́r Havlı́ček

Abstract Scanning electron microscopy was used to investigate rivulets that are formed on the analyzed surface during desorption electrospray ionization (DESI) experiment. Ferromagnetic nanoparticles added to the spray solvent in a form of colloid solution functioned as an additional surface probe. The existence of the rivulets was confirmed on glass and newly demonstrated on two different types of porous polytetrafluoroethylene (PTFE). The results show that in standard DESI set‐up the rivulets are arranged into very regular shapes. Same rivulets were obtained in DESI experiments without high voltage on the sprayer. However, no such rivulets or any other regular patterns were found on a surface in nano‐DESI (nanospray DESI without the carrier nebulizing gas) experiments. This indicates that symmetrical rivulets are created by the hydrodynamical rather than electrostatic forces. It was also demonstrated that blocking the rivulets by a simple physical barrier did not influence known surface charging effects. Copyright © 2011 John Wiley & Sons, Ltd.

10.1002/jms.1888

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Citations (11)

Lateral resolution in NALDI MSI: back to the future

Analytical and Bioanalytical Chemistry (2014)

Lukáš Krásný Oldřích Benada Marcela Strnadová Karel Lemr Vladimı́r Havlı́ček

MALDI imaging

Mass spectrometry imaging

Matrix (chemical analysis)

10.1007/s00216-014-8294-6

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Citations (8)

Electrochemical Reduction of Prometryne and the Other 2-Methylthio-4,6-dialkylamino-s-triazine Herbicides at Mercury Electrodes

Electroanalysis (1998)

Jana Skopalová Karel Lemr Milan Kotoucˇek Lubomi ́r Cˇa ́p Petr Ondra

The electrochemical behavior of the herbicide prometryne was studied in aqueous solutions by DC polarography, differential pulse and cyclic voltammetry and by constant potential coulometry. Only the protonated form of prometryne can be reduced at pH < 6.5. The electrode process includes two irreversible steps. The two-electron reduction of the C–S bond leads to its splitting and a release of methylthiol molecule. The triazine ring of the reduction product is immediately reduced under the uptake of two electrons. Both the intermediate and final products of constant potential electrolysis were identified using chromatographic techniques and mass spectrometric analysis. The reduction mechanism of other 2-methylthio-4,6-dialkylamino-s-triazines is identical.

Coulometry

Polarography

Triazine

10.1002/(sici)1521-4109(199804)10:5<331::aid-elan331>3.3.co;2-y

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Methamphetamine — properties and analytical methods of enantiomer determination

Forensic Science International (1998)

David Jirovský Karel Lemr Juraj Ševčı́k B Smysl Zdeněk Stránský

Methamphetamine

Stereocenter

Chiral stationary phase

10.1016/s0379-0738(98)00104-2

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Citations (61)

Study of the Biotransformation of Benfluron Using the Isolated Perfused Rat Liver

Acta Medica (Hradec Kralove Czech Republic) (1999)

Zbyněk Svoboda Milan Nobilis J Kvĕtina Karel Lemr

The isolated perfused rat liver method (IPRL) was used to find, isolate and identify further metabolites of Phase I and Phase II biotransformation of the potential cytostatic agent benfluron with special regard to the conjugation processes. Its pharmacokinetic profile during the perfusion was also estimated. The rat liver was isolated from the body and perfused in vitro using a recirculating perfusion system. Benfluron was added to the reservoir as a bolus in doses of 200, 100, 30 mg/kg of body weigh and 1 mg/perfusate volume and also as a continual infusion in a dose of 0.1 mg/min in separate series of experiments. The following metabolites formed during Phase I biotransformation were found in the perfusion liquid as well as in the bile: benfluron N-oxide, 9-hydroxy benfluron, demethylated 9-hydroxy benfluron, demethylated benfluron, and reduced benfluron. The major Phase II metabolite found in the bile samples was the glucuronide of 9-hydroxy benfluron. The pharmacokinetic profile of benfluron in IPRL indicated its main disposition and metabolic pathway, i.e. its rapid extraction from perfusate by the liver (t1/2 alpha = 3.76 min), 9-hydroxylation followed up O-glucuronidation and excretion to the bile. It was revealed that 12% of the total dose of the parent compound was excreted to the bile in the form of conjugates during the first hour of perfusion, 32% during 1.5 hour, and 70% during 2 hours after the administration of benfluron. The conjugates with glucuronic acid represented 96-98% of all metabolites found in the bile.

Biotransformation

Glucuronide

Hydroxylation

Bolus (digestion)

10.14712/18059694.2019.146

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Citations (2)

Signal enhancement in desorption nanoelectrospray ionization by custom‐made inlet with pressure regulation

Journal of Mass Spectrometry (2020)

Marianna Nytka Lucie Borovcová Petr Fryčák Petr Barták Karel Lemr

The efficiency of desorption/ionization becomes more critical as the sampled surface area decreases. Desorption electrospray and desorption nanoelectrospray belong to ambient ionizations and enable direct surface analysis including mass spectrometric imaging. Lateral resolution in tens of micrometers was demonstrated for desorption nanoelectrospray previously, but sensitivity of the surface scan can be an issue. For desorption electrospray, the drag force in the source is driven by the flow of used gases and vacuum suction. Ion signal intensity can be improved by controlling the nebulizing gas flow rate or auxiliary pumping of a closed compartment in front of the mass spectrometer inlet. Because nanoelectrospray generates charged droplets without the assistance of a nebulizing gas, only vacuum suction drives the gas flow. In this study, the effect of pressure drop between the atmospheric and evacuated region of a mass spectrometer on the ion signal intensity was investigated for desorption nanoelectrospray. A modification of the commercial inlet was designed. An auxiliary pump was directly connected to an inner compartment of the modified mass spectrometer inlet through a needle valve that enabled the regulation of the reduced pressure. Adjustment of the pressure drop significantly increased signal intensity (more than one order of magnitude in some cases). To a lesser extent, the temperature of a heated capillary (an integral part of the inlet) also influenced the signal intensity. The applicability of desorption nanoelectrospray equipped with pressure regulation was demonstrated by the analysis of synthetic cathinones or a pill of paracetamol. Because pressure in the inlet depends on the diameters of orifices and the power of vacuum systems of mass spectrometers, the effect of the pressure regulation can be different for different instruments. Nevertheless, the presented results confirmed the importance of pressure drop-driven transport for desorption nanoelectrospray efficiency and can encourage its new applications.

Desorption electrospray ionization

10.1002/jms.4642

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