Lech Celewicz
Adam Mickiewicz University in Poznań
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Featured researches published by Lech Celewicz.
Food and Chemical Toxicology | 2013
Violetta Krajka-Kuźniak; Jarosław Paluszczak; Lech Celewicz; Jan Barciszewski; Wanda Baer-Dubowska
The aim of this study was to evaluate the effect of phloretamide (PA), an apple constituent, on the activation of the Nrf2 transcription factor and the expression of its target genes: glutathione S-transferases (GSTs), NAD(P)H:quinone oxidoreductase-1 (NQO1) and heme oxygenase-1 (HO-1) in normal human THLE-2 hepatocytes and the hepatoma HepG2 cell line. PA did not show significant cytotoxicity towards THLE-2 cells but such an effect was observed in HepG2 cells (IC(50) ∼200μM). The treatment of cells with PA resulted in the translocation of Nrf2 from cytosol to nucleus in both cell lines, but increased the level of its transcript and protein only in THLE-2 cells. In this cell line an increased level of GSTA, GSTP, GSTT, NQO1 mRNA was also observed. Increased expression of GSTs was confirmed by enhancement of their protein levels. The increase in p53 protein content observed in THLE-2 may be associated with its stabilization induced by the enhancement of NQO1 level. PA did not affect Nrf2, GSTs, NQO1 or HO-1 expression in HepG2 cells. These results suggest that PA has rather chemopreventive than chemiotherapeutic potential and acts similarly as apple dihydrochalcones through the induction of detoxification/antioxidative enzymes.
Nucleosides, Nucleotides & Nucleic Acids | 1993
Lech Celewicz; Wojciech Urjasz; Krzysztof Golankiewicz
Abstract A series of 3′-N-substituted 3′-amino-3′-deoxythymidine derivatives with alkyl, alkenyl and alkylaryl substituents was synthesized by two methods. The first method involved the reaction of 1-(2,3-dideoxy-3-0-mesyl-5-0-trityl-β-D-threo-pentofuranosyl)thymine with an appropriate amine. In the second method, 3′-amino-5′-0-trityl-3′-deoxy-thymidine served as a synthetic precursor which was reacted with an appropiate aldehyde or ketone followed by sodium borohydride reduction. An improved synthesis of 3′-amino-3′-deoxythymidine from 3′ -azido-5′-0-trityl-3′-deoxythymidine using sodium borohydride was also described.
Synthetic Communications | 1987
Lech Celewicz; Jaros Sa; Krzysztof Golankiewicz
Abstract The convenient method for the preparation of N4-substituted cytosines is described. The irradiation with UV light of N-(1H-2-oxo-4-pyrimidinyl) amino acids provides the proper N4-substituted cytosines in a good yield.
Applied Spectroscopy | 2007
Barbara Ciesielska; Adam Łukaszewicz; Lech Celewicz; Andrzej Maciejewski; Jacek Kubicki
This paper describes a new type of spectrofluorimeter, composed of a high-performance liquid chromatography (HPLC) system directly connected to a fluorescence detector and an absorption photodiode array detector, designed for studying the emission of weakly emitting species. Procedures for measurements of emission spectra (ES), emission excitation spectra (EES), and quantum yields of emission (φE) for very weakly emitting systems (ΦE ≥ 10−7) have been proposed. The original methodical solution allows verification of whether the emission observed comes solely from the compound studied (and not from its impurities) or from some photochemical or thermal process taking place during measurements. Thanks to the use of this new type of spectrofluorimeter, it is possible to establish with a high probability that the dependence of the shape and position of the ES on the excitation wavelength and the differences between EES and absorptance spectra are due to photo-physical and/or photochemical properties of the compound studied and not due to the presence of emitting impurities. An especially interesting application of this method is to study the emission of species whose very weak emission is related to a very short lifetime as well as a low radiative rate constant. It is particularly suitable to the study of the emission properties of flexible molecules that can occur in a few conformers of different absorption and emission properties. The performance of the method is illustrated by the results of the emission studies carried out for Nα-acetyl-2-(uracil-5-yl)-L-tryptophan N-ethylamide.
Journal of Physical Organic Chemistry | 1998
Wojciech Urjasz; Lech Celewicz
The p-toluenesulfonyl (tosyl) group, an effective protector of the amine function of thymidine derivatives 2a and b, has proven to be photoremovable. This photoreaction was successfully used in the synthesis of new 5′-amino analogs of 3′-azido-3′-deoxythymidine (AZT), 6a and b. Selective photohydrolysis of 5′N-tosylamides 2a and b was carried out by UV irradiation (>300 nm) in aqueous acetonitrile in the presence of 1,5-dimethoxynaphthalene as an electron donor.
Journal of Photochemistry and Photobiology B-biology | 1998
Lech Celewicz
Abstract Irradiation of 5-fluorouracil ( 1 ) and 5-fluoro-2′-deoxyuridine ( 2 ) with N α -acetyl- L -tryptophan N -ethylamide ( 5 ) in aqueous buffered (pH 7 ) solutions led to N α -acetyl-2-(uracil-5-yl) tryptophan N -ethylamide ( 6 ) and N α -acetyl-2-[l-(2-deoxy- β -l) erythro -pentofuranosyl)uracil-5-yl] tryptophan N -ethylamide ( 7 ), respectively, as the main photoproducts. In addition, compounds 6 and 7 were synthesized by photochemical coupling of 5-bromouracil ( 3 ) and 5-bromo-2′-deoxyuridine ( 4 ), respectively, with 5 . The formation of cross-links between 5-fluorouracil-substituted nucleic acids and tryptophan-containing proteins can be detected by fluorescence characteristic of the uracil-tryptophan fluorophore. The mechanism proposed for the formation of photoproducts 6 and 7 involves electrophilic attack of the 5-uracilyl cation on the indole ring of 5.
Journal of Photochemistry and Photobiology B-biology | 1995
Lech Celewicz
Abstract The photochemical reactions of 5-bromocytosine ( 1 ), 5-bromo-1-methylcytosine ( 2 ) and 5-bromo-2′-deoxycytidine ( 3 ) with N α - acetyl- l -tryptophan N- ethylamide ( 4 ) in aqueous buffered (pH 7) solutions were studied. These photoreactions led to N α -acetyl-2-(cytosin-5-yl)tryptophan N -ethylamide ( 1a ), N α -acetyl-2-(1-methylcytosin-5-yl)tryptophan N -ethylamide ( 2a ) and N α - acetyl -2-[1-(2- deoxy -β- l - erythro-pentofuranosyl ) cytosin -5- yl ] trypophan N- ethylamide ( 3a ) respectively as the main photoproducts. Thus the coupling observed was regiospecific between the 5 position of cytosine and the 2 position of the indole ring of 4 . The structure of the photoproducts was established by spectroscopic methods ( 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy, UV spectroscopy, electron impact and liquid secondary ion mass spectrometry); in the case of 1a , additional confirmatory evidence was obtained by a chemical method (the diazotization reaction of 1a with sodium nitrite and acetic acid to give N α -acetyl-2-(uracil-5-yl)tryptophan N -ethylamide). The quantum yields of formation of the cytosine-tryptophan adducts 1a–3a ranged from 3.9 × 10 −3 to 5.4 × 10 −3 . The formation of cross-links of the type proposed here between 5-bromocytosine-substituted DNA and proteins may be detected by the characteristic fluorescence emission of the cytosine-tryptophan fluorophore. The mechanism of formation of the photoproducts 1a–3a is proposed to involve electrophilic attack of the 5-cytosinyl cation on the indole ring of 4 .
Synthetic Communications | 1985
Lech Celewicz; Henryk Koroniak
Abstract Bromination of 1,3-dimethyluracil and 6-alkyl-1,3-dimethyluracils with N-bromosuccinimide leads to the corresponding 5-bromo substituted uracils in high yields.
Journal of Peptide Science | 2014
Michal Dobkowski; Aleksandra Szychowska; Malgorzata Pieszko; Anna Miszka; Monika Wojciechowska; Magdalena Alenowicz; Jarosław Ruczyński; Piotr Rekowski; Lech Celewicz; Jan Barciszewski; Piotr Mucha
The Cu(I) catalyzed Huisgen 1,3‐dipolar azide‐alkyne cycloaddition (CuAAC) was applied for a nucleoside‐peptide bioconjugation. Systemin (Sys), an 18‐aa plant signaling peptide naturally produced in response to wounding or pathogen attack, was chemically synthesized as its N‐propynoic acid functionalized analog (Prp‐Sys) using the SPPS. Next, CuAAC was applied to conjugate Prp‐Sys with 3′‐azido‐2′,3′‐dideoxythymidine (AZT), a model cargo molecule. 1,4‐Linked 1,2,3‐triazole AZT‐Sys conjugate was designed to characterize the spreading properties and ability to translocate of cargo molecules of systemin. CuAAC allowed the synthesis of the conjugate in a chemoselective and regioselective manner, with high purity and yield. The presence of Cu(I) ions generated in situ drove the CuAAC reaction to completion within a few minutes without any by‐products. Under typical separation conditions of phosphate ‘buffer’ at low pH and uncoated fused bare‐silica capillary, an increasing peak intensity assigned to triazole‐linked AZT‐Sys conjugate was observed using capillary electrophoresis (CE) during CuAAC. CE analysis showed that systemin peptides are stable in tomato leaf extract for up to a few hours. CE‐ESI‐MS revealed that the native Sys and its conjugate with AZT are translocated through the tomato stem and can be directly detected in stem exudates. The results show potential application of systemin as a transporter of low molecular weight cargo molecules in tomato plant and of CE method to characterize a behavior of plant peptides and its analogs. Copyright
Nucleosides, Nucleotides & Nucleic Acids | 1996
Wojciech Urjasz; Lech Celewicz; Krzysztof Golankiewicz
Abstract A series of 5′-N-methanesulfonyl derivatives of 3′-azido-5′-(alkylamino)-3′,5′-dideoxythymidine was synthesised. The first step of the synthesis involved the reaction of 1-(2,5-dideoxy-5-O-tosyl-β-D-threo-pentofuranosyl)thymine 1 with an appropriate amine to give 1-[5-(alkylamino)-2,5-dideoxy-β-D-threo-pentofuranosyl]thymines 2a-e and 1-(2,5-dideoxy-β-threo-pent-4-enofuranosyl)thymine 3 as a by-product. Compounds 2a-e were treated with an excess of methanesulfonyl chloride to yield intermediates 1-[5-(dimethylamino)-3-O-methanesulfonyl-2,3,5-trideoxy-β-D-threo-pentofuranosyl]-thymine 4a and 1-[5-(N-alkyl-N-methanesulfonyl)-3-O-methanesulfonyl-2,3,5-trideoxy-β-D-threo-penfuranosyl]thymines 4b-e. The reaction of 4a-e with lithium azide in dimethyl-formamide afforded the final compounds 1-[3-azido-5-(N-methyl-N-methanesulfonyl)-2,3,5-trideoxy-β-D-erythro-penofuranosyl]thymine 5a and 1-[3-azido-5-(N-alkyl-N-methanesulfonyl)-2,3,5-trideoxy-β-D-erythro-penofuranosyl]thymines 5b-e. The independent synth...