Viktor Sándor

University of Pecs

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Ferenc Kilár

University of Pecs

Anikó Kilár

University of Pecs

ÁD

Ágnes Dörnyei

University of Pecs

Béla Kocsis

Semmelweis University

László Kollár

University of Pecs

Véronika Nagy

University of Pecs

Attila Agócs

University of Pecs

Ulrich Wellisch

Rosenheim Technical University of Applied Sciences

József Deli

University of Pecs

Lilla Makszin

University of Pecs

Cooperative Institutions

University of Pecs

University of Debrecen

Hungarian Academy of Sciences

Semmelweis University

Sapientia Hungarian University of Transylvania

University of Szeged

University of Plymouth

Universitatea Națională de Știință și Tehnologie Politehnica București

Heidelberg University

Eötvös Loránd University

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Synthesis and functionalization of 2-iodoimidazo[1,2-a]pyridines in palladium-catalysed amino-, aryloxy- and alkoxycarbonylations

Tetrahedron (2025)

Péter Szuroczki Laura Barbara Jenei Viktor Sándor Attila Bényei László Kollár

Surface Modification

10.1016/j.tet.2025.134489

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Characterization of complex, heterogeneous lipid A samples using HPLC–MS/MS technique I. Overall analysis with respect to acylation, phosphorylation and isobaric distribution

Journal of Mass Spectrometry (2016)

Viktor Sándor Ágnes Dörnyei Lilla Makszin Ferenc Kilár Zoltán Péterfi

We established a new reversed phase-high performance liquid chromatography method combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry for the simultaneous determination and structural characterization of different lipid A types in bacteria (Escherichia coli O111, Salmonella adelaide O35 and Proteus morganii O34) showing serological cross-reactivity. The complex lipid A mixtures (obtained by simple extraction and acid hydrolysis of the outer membrane lipopolysaccharides) were separated and detected without phosphate derivatization. Several previously unidentified ions were detected, which differed in the number and type of acyl chains and number of phosphate groups. In several cases, we observed the different retention of isobaric lipid A species, which had different secondary fatty acyl distribution at the C2' or the C3' sites. The fragmentation of the various, C4' monophosphorylated lipid A species in deprotonated forms provided structural assignment for each component. Fragmentation pathways of the tri-acylated, tetra-acylated, penta-acylated, hexa-acylated and hepta-acylated lipid A components and of the lipid A partial structures are suggested. As standards, the hexa-acylated ion at m/z 1716 with the E. coli-type acyl distribution and the hepta-acylated ion at m/z 1954 with the Salmonella-type acyl distribution were used. The results confirmed the presence of multiple forms of lipid A in all strains analyzed. In addition, the negative-ion mode MS permitted efficient detection for non-phosphorylated lipid A components, too. Copyright © 2016 John Wiley & Sons, Ltd.

Lipid A

10.1002/jms.3839

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Citations (23)

Carotenoid Composition of Telekia speciosa

Plants (2023)

Erzsébet Varga Viktória Lilla Balázs Viktor Sándor Attila Agócs Véronika Nagy

The carotenoid composition of the flower of Telekia speciosa was investigated for the first time by HPLC-DAD-MS. In addition to the main carotenoid lutein and its geometrical isomers, 5,6-epoxy-carotenoids, namely violaxanthin, lutein 5,6-epoxide and antheraxanthin, were detected in larger amounts. In addition, β-carotene 5,6-epoxide and β-carotene 5,6,5',6'-diepoxide were found, which occurs very rarely in plants. For unambigous identification, β-carotene 5,6-epoxide and β-carotene 5,6,5',6'-diepoxide were prepared semisynthetically, and they were characterized by 1H and 13C NMR and HPLC-CD methods.

Antheraxanthin

Violaxanthin

10.3390/plants12244116

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Characterization of complex, heterogeneous lipid A samples using HPLC‐MS/MS technique III. Positive‐ion mode tandem mass spectrometry to reveal phosphorylation and acylation patterns of lipid A

Journal of Mass Spectrometry (2017)

Viktor Sándor Anikó Kilár Ferenc Kilár Béla Kocsis Ágnes Dörnyei

Abstract In this study, we report the detailed analysis of the fragmentation patterns of positively charged lipid A species based on their tandem mass spectra obtained under low‐energy collision‐induced dissociation conditions of an electrospray quadrupole time‐of‐flight mass spectrometer. The tandem mass spectrometry experiments were performed after the separation of the compounds with a reversed‐phase high performance liquid chromatography method. We found that both, phosphorylated and nonphosphorylated lipid A molecules can be readily ionized in the positive‐ion mode by adduct formation with triethylamine added to the eluent. The tandem mass spectra of the lipid A triethylammonium adduct ions showed several product ions corresponding to inter‐ring glycosidic cleavages of the sugar residues, as well as consecutive and competitive eliminations of fatty acids, phosphoric acid, and water following the neutral loss of triethylamine. Characteristic product ions provided direct information on the phosphorylation site(s), also when phosphorylation isomers (ie, containing either a C1 or a C4′ phosphate group) were simultaneously present in the sample. Continuous series of high‐abundance B‐type and low‐abundance Y‐type inter‐ring fragment ions were indicative of the fatty acyl distribution between the nonreducing and reducing ends of the lipid A backbone. The previously reported lipid A structures of Proteus morganii O34 and Escherichia coli O111 bacteria were used as standards. Although, the fragmentation pathways of the differently phosphorylated lipid A species significantly differed in the negative‐ion mode, they were very similar in the positive‐ion mode. The complementary use of positive‐ion and negative‐ion mode tandem mass spectrometry was found to be essential for the full structural characterization of the C1‐monophosphorylated lipid A species.

Collision-induced dissociation

Lipid A

Fragmentation

10.1002/jms.4046

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Citations (13)

Biometrie

Springer eBooks (2016)

Torsten Becker Richard Herrmann Viktor Sándor Dominik Schäfer Ulrich Wellisch

10.1007/978-3-662-49407-3_7

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Separation optimization of the molecular forms of transferrin complexes by capillary zone electrohoresis

Judit Gálicza Viktor Sándor Andrea Vargová Beáta Ábrahám Szabolcs Lányi

Glicoproteina transferina serica umana (Tf) are doua loburi. Fiecare lob are un situs de legare a ionilor de fier trivalent. In urma legarii ionilor de metale si a diferitelor anioni (oxalat, aziridin-carboxilat, bicarbonat) la acest situs se pot obţine patru forme moleculare a transferinei (holo-Tf, diferri FeNTfFeC, si monoferri TfFeN, TfFeC). Experimete de electroforeza capilara de inalta performanţa (CZE) a fost utilizate pentru a separa aceste forme moleculare. Pentru a obţine o separere de inalta eficacitate a diferitelor forme moleculareobţinute in urma reacţiei de complexare am schimbat urmatoarele condiţii de separare: electrolitul, tratarea capilarelor, tensiunea. Human serum transferrin (Tf), a glycoprotein, has two lobes, each having a binding site for trivalent iron ions. The binding of metal ions and different anions (oxalate, aziridine-carboxylate, bicarbonate) to these binding site results four different molecular form of Tf (holo-Tf, diferri FeNTfFeC, and monoferri TfFeN, TfFeC). High performance capillary zone electrophoresis (CZE) experiments were performed in order to separate these molecular forms. We changed the following separation conditions: background electrolyte, capillary treatment and voltage to achieve high efficiency of separation of transferrin probes after the complexation reaction.

Carboxylate

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Characterization of isomeric lipid A species from Pseudomonas aeruginosa PAO1 by non-aqueous capillary electrophoresis with positive and negative ion electrospray tandem mass spectrometry

Arabian Journal of Chemistry (2023)

Viktor Sándor Bettina Űrmös Ibrahim Aissa Ágnes Dörnyei Anikó Kilár

Pseudomonas aeruginosa is a priority target pathogen for antibiotic research and development because of its high resistance to a wide range of antibiotics. Acquisition of resistance is sometimes associated with modifications of the lipid A component present in the outer membrane of most Gram-negative bacteria. For a deeper understanding of subtle chemical variations of lipid A in relation to biological properties, the structural elucidation of lipid A species within a bacterial strain is of crucial importance. However, the simultaneous presence of monophosphorylated positional isomers in naturally heterogeneous lipid A samples cannot easily be recognized with direct MS measurements or with conventional LC-MS strategies. Herein, we present the application of a non-aqueous capillary electrophoresis (NACE) method coupled to positive and negative ion electrospray tandem mass spectrometry with collision-induced dissociation (CID) activation technique for the in-depth analysis of the lipid A isolate of P. aeruginosa PAO1. The main advantage of our NACE strategy is its separation power regarding the site of phosphorylation of the lipid A structures, which makes it a good orthogonal technique to chromatographic characterizations of the bacterial lipid A composition, where the separation is mainly based on acylation differences of the species. Overall, the results of this electrophoretic approach revealed hitherto unreported isomeric monophosphorylated PAO1 lipid A constituents, including both phosphate and acyl chain positional isomers. The parallel fragmentation in the complementary positive and negative ion modes enabled the unequivocal assignment of the phosphorylation site and position of acyl chains in lipid A compounds of three acylation families ranging from tetra- to hexa-acylation. Moreover, C1-monophosphorylated lipid A species have been identified in P. aeruginosa for the first time.

Lipid A

Fragmentation

10.1016/j.arabjc.2023.104944

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Citations (2)

Identification of a Chimera Mass Spectrum of Isomeric Lipid A Species Using Negative Ion Tandem Mass Spectrometry

Toxins (2024)

Ágnes Dörnyei Anikó Kilár Viktor Sándor

The toxic nature of bacterial endotoxins is affected by the structural details of lipid A, including the variety and position of acyl chains and phosphate group(s) on its diglucosamine backbone. Negative-ion mode tandem mass spectrometry is a primary method for the structure elucidation of lipid A, used independently or in combination with separation techniques. However, it is challenging to accurately characterize constitutional isomers of lipid A extracts by direct mass spectrometry, as the elemental composition and molecular mass of these molecules are identical. Thus, their simultaneous fragmentation leads to a composite, so-called chimera mass spectrum. The present study focuses on the phosphopositional isomers of the classical monophosphorylated, hexaacylated Escherichia coli-type lipid A. Collision-induced dissociation (CID) was performed in an HPLC-ESI-QTOF system. Energy-resolved mass spectrometry (ERMS) was applied to uncover the distinct fragmentation profiles of the phosphorylation isomers. A fragmentation strategy applying multi-levels of collision energy has been proposed and applied to reveal sample complexity, whether it contains only a 4′-phosphorylated species or a mixture of 1- and 4′-phosphorylated variants. This comparative fragmentation study of isomeric lipid A species demonstrates the high potential of ERMS-derived information for the successful discrimination of co-ionized phosphorylation isomers of hexaacylated lipid A.

Fragmentation

Collision-induced dissociation

Structural isomer

10.3390/toxins16070322

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Analgesic topical capsaicinoid therapy increases somatostatin-like immunoreactivity in the human plasma

Neuropeptides (2014)

Katalin Horváth Melinda Boros Teréz Bagoly Viktor Sándor Ferenc Kilár

Oswestry Disability Index

10.1016/j.npep.2014.10.001

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Citations (12)

Carotenoid profile of two capsorubin-rich tropical plants

Journal of Food Composition and Analysis (2021)

Enrique Murillo József Deli Véronika Nagy Eunice Molinar‐Toribio Viktor Sándor

Jipi-japa (Carludovica palmata) and zamia (Zamia dressleri) are endemic species and are found mostly in the forests of Central America including Panamá. In theory both the jipi-japa fruit and the stem and seeds of zamia are edible, although were only consumed occasionally mostly before modern times. The complete and detailed carotenoid analysis of the fruits of jipi-japa and the brown leaves of zamia was achieved using HPLC-DAD-MS technique, and co-chromatography with authentic samples. Plant extracts were subjected to HPLC separation on both C30 and C18 columns to make possible a better identification. Altogether 22 components were detected and 15 identified from the total extract of jipi-japa, and 32 components were detected and 17 identified from the extract of brown zamia leaves. From the identified carotenoids quite a number has special structures, which have recently been described in some of our previous papers on Central American plants (Murillo et al., 2011a, 2018; Gulyás-Fekete et al., 2013). It was found that almost 50 % of the total carotenoid content can be attributed to capsorubin in both plants. This carotenoid is present usually as a minor (2–3 %) carotenoid in other sources such as red pepper. Other carotenoids with κ end group are present in significant amounts, as well. Total carotenoid content was determined as the sum of yellow and red carotenoids (see Supplement). The main carotenoid, capsorubin, was isolated by open column chromatography on calcium carbonate and aluminium oxide and characterized by UV–vis, 1H and 13C NMR methods and compared to literature data. Capsorubin is a potent antioxidant even among carotenoids and have important biological effects. These two plants could be good sources for capsorubin either for isolation in gram amounts or for direct consumption.

10.1016/j.jfca.2020.103798

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Citations (10)