Ján Imrich - Academia.edu (original) (raw)
Papers by Ján Imrich
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A series of 1-acyl-4-phenyl/(acridin-9-yl)thiosemicarbazides 3, including four new compounds, wer... more A series of 1-acyl-4-phenyl/(acridin-9-yl)thiosemicarbazides 3, including four new compounds, were prepared in order to study substituent effects on cyclization reactions with oxalyl chloride (producing imidazolidine-4,5-diones 4), dimethyl acetylenedicarboxylate (to give thiazolidin-4-ones 7 and 8) and autocondensation under alkaline conditions (to yield 1,2,4-triazoles 9). A positional isomer, 10 of compound 3f was also prepared. Altogether, twenty new compounds characterized and identified by IR, UV, 1 H, 13 C and 2D NMR and quantum chemical calculations are described. The tautomerism of the products and regioselectivity of the reactions were evaluated. Compounds 3f−h, 3h•2HCl, 7b,d and 10 were screened for cytotoxic activity against the L1210 leukemia cell line and all compounds, except for 3f, exhibited promising inhibitions of cell growth.
New J. Chem., 2017
The interaction of aminomethylphosphonic acid with the Zn(ii)–cyclen complex was evaluated by an ... more The interaction of aminomethylphosphonic acid with the Zn(ii)–cyclen complex was evaluated by an original combination of potentiometry and multinuclear NMR.
Journal of Colloid and Interface Science, 2017
The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals... more The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals is reported. L-cysteine and polyvinylpyrrolidone (PVP) were used as capping agents. When using L-cysteine, the dissolution of cadmium(II) was almost none for CdS/ZnS nanocrystals. Moreover, prepared CdS-, and CdS/ZnS-cysteine nanosuspensions exhibited unimodal particle size distributions with very good stability, which was further supported by the zeta potential measurements. The Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy showed the successful embedment of cysteine into the structure of the nanocrystals. Additionally, the optical properties were examined, and the results showed that the cysteine nanosuspension has promising fluorescence properties. On the other hand, PVP was not determined to be a very suitable capping agent for the present system. In this case, the release of cadmium (II) was higher in comparison to the L-cysteine capped samples. The nanosuspensions were successfully used for in vitro studies on selected cancer cell lines. Using fluorescence microscopy, it was evidenced that the nanocrystals enter the cell and that they can serve as imaging agents in biomedical applications.
Acta Chimica Slovaca, 2015
New photosensitizers are needed for photodynamic antimicrobial and anticancer chemotherapy. Two n... more New photosensitizers are needed for photodynamic antimicrobial and anticancer chemotherapy. Two new groups of proflavine derivatives have been recently prepared and their action on the cancer cells has been investigated by our research team. In this paper, we studied an effect of UV-A irradiation of two groups of proflavines: 3,6-bis((1-alkyl-5-oxo-imidazolidin-2-yliden)imino)acridine hydrochlorides (AcrDIMs) and 1’,1”-(acridin-3,6-diyl)-3’,3”-dialkyldithiourea hydrochlorides (AcrDTUs) on a plasmid DNA (pDNA). These compounds induced a photocleavage of pDNA characteristic by generation of free radicals, single strand DNA breaks and formation of an open circular form of pDNA.
Magnetic resonance in chemistry : MRC, Jan 14, 2015
Very strong proton deshielding was found in di/tri-aromatic isoxazoline regioisomers prepared fro... more Very strong proton deshielding was found in di/tri-aromatic isoxazoline regioisomers prepared from acridin-4-yl dipolarophiles and stable benzonitrile oxides (BNO). Three alkenes, (acridin-4-yl)-CHCH-R (R = COOCH3 , Ph, and CONH2 ), reacted with three BNO dipoles (2,4,6-trimethoxy, 2,4,6-trimethyl, 2,6-dichloro) to give pairs of target isoxazolines with acridine bound to C-4 or C-5 carbon of the isoxazoline (denoted as 4-Acr or 5-Acr). Regioselectivity was dependent on both the dipolarophile and dipole character. The ester and amide dipolarophile displayed variable regioselectivity in cycloadditions whereas the styrene one afforded prevailing 4-Acr regioisomers. 2,4,6-Trimethoxy-BNO was most prone to form 5-Acr isoxazolines while mesitonitrile oxide gave major 4-Acr isoxazolines. Basic hydrolysis of the amide cycloadduct led to an unexpected isoxazolone product. The structure of the target compounds was studied by NMR, MS, and X-ray crystallography. Copyright © 2015 John Wiley & So...
Acta crystallographica. Section C, Crystal structure communications, 2005
In the title compound, C18H16N4OS, prepared by the reaction of 4-(acridin-9-yl)-1,1-dimethylthios... more In the title compound, C18H16N4OS, prepared by the reaction of 4-(acridin-9-yl)-1,1-dimethylthiosemicarbazide with methyl bromoacetate, the acridine and thiazolidine ring systems are both non-planar and, because of steric requirements, almost perpendicular, with a dihedral angle between their planes of 99.69 (6) degrees. C-H...O and C-H...pi(arene) hydrogen bonds stabilize the crystal structure in the solid state.
Zeitschrift für Naturforschung C, 2012
![Research paper thumbnail of Asymmetric induction in a new domino reaction of [3,3]-sigmatropic rearrangement of allylic thiocyanates and intramolecular heterocyclisation](https://attachments.academia-assets.com/89164654/thumbnails/1.jpg)
](Tetrahedron, 2002
ÐA new synthetic route to diastereomerically pure (4S,5S)-4-vinyltetrahydro-1H-2-imidazolethiones... more ÐA new synthetic route to diastereomerically pure (4S,5S)-4-vinyltetrahydro-1H-2-imidazolethiones via a novel domino reaction of [3,3]-sigmatropic rearrangement of chiral thiocyanates followed by stereoselective intramolecular amine addition to arising isothiocyanates is reported.
Tetrahedron, 2014
ABSTRACT Novel acridine spirocompounds, spiro[dihydroacridine-9′(10′H),5-imidazolidine]-2-thiones... more ABSTRACT Novel acridine spirocompounds, spiro[dihydroacridine-9′(10′H),5-imidazolidine]-2-thiones have been prepared by the spontaneous cyclization of 1-substituted 3-(acridin-9-ylmethyl)thioureas, which were obtained from 1-(acridin-9-yl)methanamine, N-(acridin-9-ylmethyl)propan-1-amine, and N-(acridin-9-ylmethyl)benzylamine and alkyl/aryl isothiocyanates, as continuation of our previous studies on new acridine spirocycles. Imidazolidine-2-thiones thus obtained were subsequently transformed with mesitylnitrile oxide to imidazolidine-2-one analogues, some of which partly reopened to the corresponding (acridin-9-ylmethyl)ureas. An unusual spirocyclization via a CH carbanion instead of the N-1 nitrogen has been found for 3-(acridin-9-ylmethyl)-1-(acridin-9-yl)thioureas possessing two acridine rings. Structural modifications in positions 1, 3, and 4 of the spiro ring together with 1H, 13C, and 15N NMR spectroscopy and X-ray crystallography have been employed to rationalize a general propensity of various 9-substituted acridines to undergo easy spirocyclization.
Collection of Czechoslovak Chemical Communications, 1987
N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocy... more N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocyclizations with lower yields than those obtained from analogous N',N'-disubstituted derivatives. This decreased reactivity is caused by the existence of a six-membered cyclic form with the very strong hydrogen bond NH···O=C. The possibility of formation of various conformers has been found with N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives as a consequence of the rotation around the C(2)-C(O) connecting line.
Collection of Czechoslovak Chemical Communications, 2007
Two types of (acridin-9-yl)thiosemicarbazides with the acridine moiety in the thiourea part (Acr-... more Two types of (acridin-9-yl)thiosemicarbazides with the acridine moiety in the thiourea part (Acr-NHCS, 10a, 10b) and hydrazine part (Acr-NHNHCS, 12a-12c) were prepared to investigate their reactions with dimethyl acetylenedicarboxylate. Five-membered thiazolidinone derivatives 15a, 15b, 19a-19c were formed; some aspects of corresponding reaction mechanisms are discussed. 1D and 2D 1H and 13C NMR spectroscopy and DFT quantum chemical calculations were used to elucidate the structure of the compounds.
Collection of Czechoslovak Chemical Communications, 1991
Kinetics of nucleophilic additions of butylamine to phenylsulfonyl isothiocyanate was investigate... more Kinetics of nucleophilic additions of butylamine to phenylsulfonyl isothiocyanate was investigated by the stopped-flow UV spectroscopic method and the transfer of electronic effects of substituents on the reaction centre through the SO2 group was examined. The structure and the polar character of SO2NCS, NCS and SO2 groups is discussed.
Collection of Czechoslovak Chemical Communications, 1983
Bromine oxidation of N-(3 or 4-substituted phenyl)-N'-3-phenylpropenoylthioureas in chlorofor... more Bromine oxidation of N-(3 or 4-substituted phenyl)-N'-3-phenylpropenoylthioureas in chloroform afforded either derivatives of benzylidenethiazoline or benzothiazole depending on the structure of the aniline residue. The structure of the title products was proved by elemental analysis, IR, 1H NMR and 13C NMR spectral data.
Collection of Czechoslovak Chemical Communications, 1986
3-Butine-2-methyl-2-ol reacts with isothiocyanates in the presence of sodium hydride in dimethylf... more 3-Butine-2-methyl-2-ol reacts with isothiocyanates in the presence of sodium hydride in dimethylformamide to give various products depending on structure of the isothiocyanate residue. Isothiocyanates with the NCS group bound to sp2 carbon atom (phenyl, 4-bromophenyl, and styryl isothiocyanates) give the respective 1,3-oxazolidine derivatives. If the NCS group is bound to an sp3-hybridized carbon atom (ethyl and benzyl isothiocyanates), derivatives of 1,3-oxathiolane are formed. Acyl isothiocyanates (benzoyl and 3-phenylpropenoyl isothiocyanates) give products of substitution of the NCS group, viz. 1-butine-3-methyl-3-yl benzoate and 3-phenylpropenoic anhydride.
Bioorganic & Medicinal Chemistry, 2012
Three new acridine-thiazolidinone derivatives (2a-2c) have been synthesized and their interaction... more Three new acridine-thiazolidinone derivatives (2a-2c) have been synthesized and their interactions with calf thymus DNA and a number of cell lines (leukemic cells HL-60 and L1210 and human epithelial ovarian cancer cell lines A2780) were studied. The compounds 2a-2c possessed high affinity to calf thymus DNA and their binding constants determined by spectrofluorimetry were in the range of 1.37 Â 10 6-5.89 Â 10 6 M À1. All of the tested derivatives displayed strong cytotoxic activity in vitro, the highest activity in cytotoxic tests was found for 2c with IC 50 = 1.3 ± 0.2 lM (HL-60), 3.1 ± 0.4 lM (L1210), and 7.7 ± 0.5 lM (A2780) after 72 h incubation. The cancer cells accumulated acridine derivatives very fast and the changes of the glutathione level were confirmed. The compounds inhibited proliferation of the cells and induced an arrest of the cell cycle and cell death. Their influence upon cells was associated with their reactivity towards thiols and DNA binding activity.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A series of 1-acyl-4-phenyl/(acridin-9-yl)thiosemicarbazides 3, including four new compounds, wer... more A series of 1-acyl-4-phenyl/(acridin-9-yl)thiosemicarbazides 3, including four new compounds, were prepared in order to study substituent effects on cyclization reactions with oxalyl chloride (producing imidazolidine-4,5-diones 4), dimethyl acetylenedicarboxylate (to give thiazolidin-4-ones 7 and 8) and autocondensation under alkaline conditions (to yield 1,2,4-triazoles 9). A positional isomer, 10 of compound 3f was also prepared. Altogether, twenty new compounds characterized and identified by IR, UV, 1 H, 13 C and 2D NMR and quantum chemical calculations are described. The tautomerism of the products and regioselectivity of the reactions were evaluated. Compounds 3f−h, 3h•2HCl, 7b,d and 10 were screened for cytotoxic activity against the L1210 leukemia cell line and all compounds, except for 3f, exhibited promising inhibitions of cell growth.
New J. Chem., 2017
The interaction of aminomethylphosphonic acid with the Zn(ii)–cyclen complex was evaluated by an ... more The interaction of aminomethylphosphonic acid with the Zn(ii)–cyclen complex was evaluated by an original combination of potentiometry and multinuclear NMR.
Journal of Colloid and Interface Science, 2017
The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals... more The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals is reported. L-cysteine and polyvinylpyrrolidone (PVP) were used as capping agents. When using L-cysteine, the dissolution of cadmium(II) was almost none for CdS/ZnS nanocrystals. Moreover, prepared CdS-, and CdS/ZnS-cysteine nanosuspensions exhibited unimodal particle size distributions with very good stability, which was further supported by the zeta potential measurements. The Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy showed the successful embedment of cysteine into the structure of the nanocrystals. Additionally, the optical properties were examined, and the results showed that the cysteine nanosuspension has promising fluorescence properties. On the other hand, PVP was not determined to be a very suitable capping agent for the present system. In this case, the release of cadmium (II) was higher in comparison to the L-cysteine capped samples. The nanosuspensions were successfully used for in vitro studies on selected cancer cell lines. Using fluorescence microscopy, it was evidenced that the nanocrystals enter the cell and that they can serve as imaging agents in biomedical applications.
Acta Chimica Slovaca, 2015
New photosensitizers are needed for photodynamic antimicrobial and anticancer chemotherapy. Two n... more New photosensitizers are needed for photodynamic antimicrobial and anticancer chemotherapy. Two new groups of proflavine derivatives have been recently prepared and their action on the cancer cells has been investigated by our research team. In this paper, we studied an effect of UV-A irradiation of two groups of proflavines: 3,6-bis((1-alkyl-5-oxo-imidazolidin-2-yliden)imino)acridine hydrochlorides (AcrDIMs) and 1’,1”-(acridin-3,6-diyl)-3’,3”-dialkyldithiourea hydrochlorides (AcrDTUs) on a plasmid DNA (pDNA). These compounds induced a photocleavage of pDNA characteristic by generation of free radicals, single strand DNA breaks and formation of an open circular form of pDNA.
Magnetic resonance in chemistry : MRC, Jan 14, 2015
Very strong proton deshielding was found in di/tri-aromatic isoxazoline regioisomers prepared fro... more Very strong proton deshielding was found in di/tri-aromatic isoxazoline regioisomers prepared from acridin-4-yl dipolarophiles and stable benzonitrile oxides (BNO). Three alkenes, (acridin-4-yl)-CHCH-R (R = COOCH3 , Ph, and CONH2 ), reacted with three BNO dipoles (2,4,6-trimethoxy, 2,4,6-trimethyl, 2,6-dichloro) to give pairs of target isoxazolines with acridine bound to C-4 or C-5 carbon of the isoxazoline (denoted as 4-Acr or 5-Acr). Regioselectivity was dependent on both the dipolarophile and dipole character. The ester and amide dipolarophile displayed variable regioselectivity in cycloadditions whereas the styrene one afforded prevailing 4-Acr regioisomers. 2,4,6-Trimethoxy-BNO was most prone to form 5-Acr isoxazolines while mesitonitrile oxide gave major 4-Acr isoxazolines. Basic hydrolysis of the amide cycloadduct led to an unexpected isoxazolone product. The structure of the target compounds was studied by NMR, MS, and X-ray crystallography. Copyright © 2015 John Wiley & So...
Acta crystallographica. Section C, Crystal structure communications, 2005
In the title compound, C18H16N4OS, prepared by the reaction of 4-(acridin-9-yl)-1,1-dimethylthios... more In the title compound, C18H16N4OS, prepared by the reaction of 4-(acridin-9-yl)-1,1-dimethylthiosemicarbazide with methyl bromoacetate, the acridine and thiazolidine ring systems are both non-planar and, because of steric requirements, almost perpendicular, with a dihedral angle between their planes of 99.69 (6) degrees. C-H...O and C-H...pi(arene) hydrogen bonds stabilize the crystal structure in the solid state.
Zeitschrift für Naturforschung C, 2012
Tetrahedron, 2002
ÐA new synthetic route to diastereomerically pure (4S,5S)-4-vinyltetrahydro-1H-2-imidazolethiones... more ÐA new synthetic route to diastereomerically pure (4S,5S)-4-vinyltetrahydro-1H-2-imidazolethiones via a novel domino reaction of [3,3]-sigmatropic rearrangement of chiral thiocyanates followed by stereoselective intramolecular amine addition to arising isothiocyanates is reported.
Tetrahedron, 2014
ABSTRACT Novel acridine spirocompounds, spiro[dihydroacridine-9′(10′H),5-imidazolidine]-2-thiones... more ABSTRACT Novel acridine spirocompounds, spiro[dihydroacridine-9′(10′H),5-imidazolidine]-2-thiones have been prepared by the spontaneous cyclization of 1-substituted 3-(acridin-9-ylmethyl)thioureas, which were obtained from 1-(acridin-9-yl)methanamine, N-(acridin-9-ylmethyl)propan-1-amine, and N-(acridin-9-ylmethyl)benzylamine and alkyl/aryl isothiocyanates, as continuation of our previous studies on new acridine spirocycles. Imidazolidine-2-thiones thus obtained were subsequently transformed with mesitylnitrile oxide to imidazolidine-2-one analogues, some of which partly reopened to the corresponding (acridin-9-ylmethyl)ureas. An unusual spirocyclization via a CH carbanion instead of the N-1 nitrogen has been found for 3-(acridin-9-ylmethyl)-1-(acridin-9-yl)thioureas possessing two acridine rings. Structural modifications in positions 1, 3, and 4 of the spiro ring together with 1H, 13C, and 15N NMR spectroscopy and X-ray crystallography have been employed to rationalize a general propensity of various 9-substituted acridines to undergo easy spirocyclization.
Collection of Czechoslovak Chemical Communications, 1987
N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocy... more N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocyclizations with lower yields than those obtained from analogous N',N'-disubstituted derivatives. This decreased reactivity is caused by the existence of a six-membered cyclic form with the very strong hydrogen bond NH···O=C. The possibility of formation of various conformers has been found with N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives as a consequence of the rotation around the C(2)-C(O) connecting line.
Collection of Czechoslovak Chemical Communications, 2007
Two types of (acridin-9-yl)thiosemicarbazides with the acridine moiety in the thiourea part (Acr-... more Two types of (acridin-9-yl)thiosemicarbazides with the acridine moiety in the thiourea part (Acr-NHCS, 10a, 10b) and hydrazine part (Acr-NHNHCS, 12a-12c) were prepared to investigate their reactions with dimethyl acetylenedicarboxylate. Five-membered thiazolidinone derivatives 15a, 15b, 19a-19c were formed; some aspects of corresponding reaction mechanisms are discussed. 1D and 2D 1H and 13C NMR spectroscopy and DFT quantum chemical calculations were used to elucidate the structure of the compounds.
Collection of Czechoslovak Chemical Communications, 1991
Kinetics of nucleophilic additions of butylamine to phenylsulfonyl isothiocyanate was investigate... more Kinetics of nucleophilic additions of butylamine to phenylsulfonyl isothiocyanate was investigated by the stopped-flow UV spectroscopic method and the transfer of electronic effects of substituents on the reaction centre through the SO2 group was examined. The structure and the polar character of SO2NCS, NCS and SO2 groups is discussed.
Collection of Czechoslovak Chemical Communications, 1983
Bromine oxidation of N-(3 or 4-substituted phenyl)-N'-3-phenylpropenoylthioureas in chlorofor... more Bromine oxidation of N-(3 or 4-substituted phenyl)-N'-3-phenylpropenoylthioureas in chloroform afforded either derivatives of benzylidenethiazoline or benzothiazole depending on the structure of the aniline residue. The structure of the title products was proved by elemental analysis, IR, 1H NMR and 13C NMR spectral data.
Collection of Czechoslovak Chemical Communications, 1986
3-Butine-2-methyl-2-ol reacts with isothiocyanates in the presence of sodium hydride in dimethylf... more 3-Butine-2-methyl-2-ol reacts with isothiocyanates in the presence of sodium hydride in dimethylformamide to give various products depending on structure of the isothiocyanate residue. Isothiocyanates with the NCS group bound to sp2 carbon atom (phenyl, 4-bromophenyl, and styryl isothiocyanates) give the respective 1,3-oxazolidine derivatives. If the NCS group is bound to an sp3-hybridized carbon atom (ethyl and benzyl isothiocyanates), derivatives of 1,3-oxathiolane are formed. Acyl isothiocyanates (benzoyl and 3-phenylpropenoyl isothiocyanates) give products of substitution of the NCS group, viz. 1-butine-3-methyl-3-yl benzoate and 3-phenylpropenoic anhydride.
Bioorganic & Medicinal Chemistry, 2012
Three new acridine-thiazolidinone derivatives (2a-2c) have been synthesized and their interaction... more Three new acridine-thiazolidinone derivatives (2a-2c) have been synthesized and their interactions with calf thymus DNA and a number of cell lines (leukemic cells HL-60 and L1210 and human epithelial ovarian cancer cell lines A2780) were studied. The compounds 2a-2c possessed high affinity to calf thymus DNA and their binding constants determined by spectrofluorimetry were in the range of 1.37 Â 10 6-5.89 Â 10 6 M À1. All of the tested derivatives displayed strong cytotoxic activity in vitro, the highest activity in cytotoxic tests was found for 2c with IC 50 = 1.3 ± 0.2 lM (HL-60), 3.1 ± 0.4 lM (L1210), and 7.7 ± 0.5 lM (A2780) after 72 h incubation. The cancer cells accumulated acridine derivatives very fast and the changes of the glutathione level were confirmed. The compounds inhibited proliferation of the cells and induced an arrest of the cell cycle and cell death. Their influence upon cells was associated with their reactivity towards thiols and DNA binding activity.