Papers by Ludovic Kurunczi
Revista de Chimie, 2008
The relationship between the structure and biological activity (toxicity) SAR of the stoichiometr... more The relationship between the structure and biological activity (toxicity) SAR of the stoichiometric mixtures between anion and cation (or neutral species) proceeded at pH 8.2 from the different amine salts of benzoic, acetic, oxalic, naphthalene carboxylic acids was determined. Their toxicity was determined by using the metamorphosis (transformation) process of the marine invertebrate Hydractinia echinata (Hydrozoa, Cnidaria) from the freely swimming larva to a sessile polyp as a biological test system. The two components of the stoichiometric mixture, the anion and the cation or neutral species react independently, but in a parallel way, the effectiveness of the cation/neutral species being superior. The studied compounds were grouped by their cationic/neutral structure and measured toxicity. All of these series were also characterized by a calculated mean value of the toxicity. The marine organism, Hydractinia echinata was a good and advantageous alternative for the toxicity testi...
Quantitative Structure-Activity Relationships, 1993
Abbreviations: MTD, Minimal steric (topological) difference method; also an approximative measure... more Abbreviations: MTD, Minimal steric (topological) difference method; also an approximative measure for molecule-receptor site steric misfit; Ai experimental activities; Ai calculated activities; S receptor map; j numbering of vertices in the hypermolecule; cj =-1, 0, +I, vertex attribution to receptor cavity, receptor wall and exterior region, respectively; cr Hammett constant; I[ Hansch hydrophobicity; E, Taft constant.
Journal of Molecular Structure: THEOCHEM, 1996
Multiple linear regression analysis has been used to identify the most important properties relev... more Multiple linear regression analysis has been used to identify the most important properties relevant to psychotomimetic activity displayed by 37 phenylalkylamines. Using the minimal topologic differences (MTD) parameter, lipophilicity (log P, calculated by using 7r Hansch substituent terms), average electrostatic field (AEF) and electronic descriptors, lowest unoccupied molecular orbital energies (E ruMo) and net atomic charges (obtained from AM1 calculations), good correlations with biological activity were obtained (R* = 0.79-0.92). Cross-validation procedure was applied indicating a good predictability of the proposed models (I?; = 0.67-0.81).
Quantitative Structure-Activity Relationships, 1995
A "testkit" series of 27 derivatives of cAMP with various substituents in position 1, 2, 6 and 8 ... more A "testkit" series of 27 derivatives of cAMP with various substituents in position 1, 2, 6 and 8 and within the purine cycle, thiophosphoric acid derivatives (with equatorial or axial S-atom) also included, were used to map four receptor sites of the R-subunit of CAMP dependent phosphokinases I and 11, namely labile and stable receptors AI, BI, A11 and BII. A QSAR by the MTD method was applied for the four series of activities, together with the relative nitrogen base hydrophobicity (IgK,). electric charge of the position Gsubstituent (qNi) and an indicator variable (6 = 1 for equatorial thiophosphoric derivatives). Correlation coefficients between r = 0.836 and 0.948 were obtained and the reliability of QSAR results was tested by a cross validation-like procedure. Characteristic steric features (concerning the effects of substituents in different nitrogen-base positions) were separately obtained for each receptor. For A1 and BI receptor there is a negatively charged receptor group interacting with substituents in position 6 of CAMP derivatives. BI and BII receptors are of a marked hydrophobic character. Thiophosphoric acid derivatives, especially those with equatorial S-atom, have a decreased affinity for all four receptors. The results are compared with other QSAR studies of our group, concerning different series of CAMP derivatives.
SAR and QSAR in Environmental Research, 1995
QSARs by the Minimal Steric/Topologic Difference (MTD)-method were performed for general toxicity... more QSARs by the Minimal Steric/Topologic Difference (MTD)-method were performed for general toxicity, hepatic cytosol receptor binding and aryl hydrocarbon hydroxylase induction on polychlorinated and polybrominated derivatives of dibenzo-p-dioxin, dibenzofuran and biphenyl. Low energy conformations selected by molecular mechanics calculations and superpositions of the considered structures for the construction of the hypermolecule were performed using the COSMIC molecular modelling package. The
Journal of Plant Interactions, 2007
Benzoates and particularly, benzoic acids are known biologically for their effects in the regulat... more Benzoates and particularly, benzoic acids are known biologically for their effects in the regulation of seed germination. A series of monoethanolamine salts of para-substituted benzoic acids (MEASPBAs), the corresponding acids (BAs) and monoethanolamine (MEA) were tested at different concentrations, on Cucumis sativus L. germination in order to assess their biological activity. The correlation between the effects of different substituents of these salts and the corresponding acids with germination rate, root and shoot length, fresh and dry biomass, soluble protein content, isocitrate lyase (ICL, EC 4.1.3.1) and catalase (CAT, EC 1.11.1.6.) activity, was evaluated. Data showed that p-OH and p-CH 3 substituents had a lower inhibitory effect compared to the halogenated substituents. Moreover, the inhibition of root and shoot lengths and the dramatic decrease of fresh biomass for halogenated (p-Cl, p-Br, p-I) MEASPBAs and BAs followed the increase of the atomic size of the substituent.
Journal of Chemical Information and Modeling, 2002
The PLS variant of the MTD method (T. I. Oprea et al., SAR QSAR Environ. Res. 2001, 12, 75-92) wa... more The PLS variant of the MTD method (T. I. Oprea et al., SAR QSAR Environ. Res. 2001, 12, 75-92) was applied to a series of 25 acetylcholinesterase hydrolysis substrates. Statistically significant MTD-PLS models (q(2) between 0.7 and 0.8) are in agreement with previous MTD models, with the advantage that local contributions are understood beyond the occupancy/nonoccupancy interpretation in MTD. A "chemically intuitive" approach further forces MTD-PLS coefficients to assume only negative (or zero) values for fragmental volume descriptors and positive (or zero) values for fragmental hydrophobicity descriptors. This further separates the various kinds of local interactions at each vertex of the MTD hypermolecule, making this method suitable for medicinal chemistry synthesis planning.
International Journal of Quantum Chemistry, 2007
... Other Resources. A preliminary MTD-PLS study for androgen receptor binding of steroid compoun... more ... Other Resources. A preliminary MTD-PLS study for androgen receptor binding of steroid compounds. Alina Bora 1,* ,; E. Seclaman 2 ,; L. Kurunczi 2,* ,; Simona Funar-Timofei 1. ... Z.; Chiriac, A.; Holban, S.; Ciubotaru, D.; Mihalas, GI Research Studies Press: Letchworth, 1984; 110. ...
Dyes and Pigments, 1996
Lipophilicity in cellulose dyeing has been modelled by correlations of dye structural parameter w... more Lipophilicity in cellulose dyeing has been modelled by correlations of dye structural parameter with dye affinity and lipophilic dye parameters. In a series of anionic azo dyes hydrophobic interactions in dye-fibre binding only appeared in two subseries of dyes ...
Dyes and Pigments, 1997
Eutrophication is one of the main causes of the degradation of lake ecosystems. In this paper, mu... more Eutrophication is one of the main causes of the degradation of lake ecosystems. In this paper, multiple linear regression (MLR) and neural network (NN) methods were developed as empirical models to predict chlorophyll-a (Chl-a) concentrations in Lake Champlain. The models were developed using a large dataset collected from Lake Champlain over a 24-year period from 1992 to 2016. The dataset consisted of monitoring depth (Depth), total phosphorus (TP), total nitrogen (TN), alkalinity (RegAlk), temperature (TempC), chloride (Cl) and secchi depth (Secchi). Statistical analyses showed that TP, Secchi, TN and Depth demonstrated strong relationships with Chl-a concentrations. The simulation results revealed that both the MLR and NN models performed well in predicting Chl-a concentrations, especially for low to moderate concentrations of Chl-a (< 7.5 μg/L). The NN model showed better accuracy and generalization performance in comparison with the MLR model for both the training and verification processes. In addition, both the developed MLR and NN models produce good results when used to predict Chl-a concentrations from 2017 to 2021. However, neither the MLR nor NN models can accurately predict high Chl-a concentrations (> 7.5 μg/L). These models can be useful for improving lake management and providing early warnings regarding the problem of eutrophication.
Dyes and Pigments, 2000
The structure of cellulose ®bre is discussed in relation to the relevance of the ligand±receptor ... more The structure of cellulose ®bre is discussed in relation to the relevance of the ligand±receptor concept for dye±®bre binding. An outline of qualitative SAR (structure±activity relationship) for dye±cellulose ®bre binding is given, as well as of QSAR/QSPR (quantitative structure±activity/property relationship) for such binding and calculations of pertinent (electronic, geometric and partition) properties of dye molecules. Modern QSAR methods for dye±®bre adsorption include MTD (minimal steric dierence) analysis, CoMFA (comparative molecular ®eld analysis), PCRA (principal component regression analysis) and neural network. Series of anthraquinone vat dyes, mono, bisazo and disperse dyes were studied by these methods. Conclusions from these QSAR studies concerning the eect of structural features of dye molecules upon adsorption on cellulose ®bres are discussed.
Central European Journal of Chemistry, 2013
Partial Least Squares Discriminant Analysis (PLS-DA) is employed to obtain novel combinations of ... more Partial Least Squares Discriminant Analysis (PLS-DA) is employed to obtain novel combinations of energetic terms present in classical scoring functions, which exceed and compensates the “traditional” consensus scheme. These novel scoring functions were involved to rank the database of indirubin inhibitors of glycogen synthase kinase-3β and cyclin dependent kinase-2 decoys from Directory of Useful Decoys. The ability of docking-scoring algorithm to prioritize the actives is assessed by means of several metrics. The best classification function includes donor component of Chemgauss2, steric contribution from Chemgauss3 and rotatable bond term of ScreenScore and provide significant improvement of enrichment factor at 5% of database.
Quantitative Structure-Activity Relationships, 1995
Dye-fibre binding was modelled by principal-component-regression analysis (PCRA) method for two s... more Dye-fibre binding was modelled by principal-component-regression analysis (PCRA) method for two series of 46, respectively 49 anthraquinone vat dyes. Robust equations with predictive modelling power were proposed for the correlations with structural parameters (2 = 0.92 and s = 0.48, respectively 2 = 0.94 and * To receive all correspondence mated and used instead of the original regressors. The OLS regression is applied to estimate the regression matrix of the regressunds
GSK-3 (Glycogen synthase kinase-3) is a serine/threonine protein kinase involved in various physi... more GSK-3 (Glycogen synthase kinase-3) is a serine/threonine protein kinase involved in various physiological processes and its inhibitors have been evaluated as promising drug candidates for severe pathologies. In this paper a PLS regression analysis was used, to explore the relationship between field of descriptors (as independent variable) and biological activities (pIC50 as dependent variables). The main purpose of this work is to develop a robust QSAR model for predicting inhibitory activity of the 109 indirubin derivatives and better understanding of structural features of these compounds and their relation with the inhibitory activity using the Dragon descriptors. The statistical qualities of the final model have been assessed by several parameters such as: the cumulative sum of squares of correlation coefficient RY(CUM)=0.872, the cumulative fraction of the total variation of the Y values that can be predicted for all the extracted principal components by cross validation Q2(CUM...
The metallic elements concentrations of medicinal plants (coriander, dill, Echinacea, lavender, c... more The metallic elements concentrations of medicinal plants (coriander, dill, Echinacea, lavender, chamomile, mint, and plantain, used for phytopharmaceutical products), cultivated in unpolluted region, were analyzed by neutron activation analysis. The essential nutrients, macro-, micro-, and trace elements (K, Ca, Mg, Na, Fe, Mn, Rb, Sr, and Zn), potentially toxic elements (Al, As, Ba, Co, Sb, Cr, and V), and rare earth elements were monitored and were compared with those presented in the literature. An estimation of their contributions to intake and toxicity for a person was made, which revealed that (a) teas prepared from the examined plants represent useful contribution to the food provided intake of three essential macronutrients (K, Ca, and Mg); (b) the Cu, Mn, Rb, Sr, Zn, and rare earths levels are normal or low; (c) the quantities of As, Ba, Co, Sb, Cr, and V do not represent toxicological concerns; (d) the examination of the estimated Al and Fe quantities recovered in infusion...
Revue Roumaine De Chimie, 2006
This is a review on studies in QSAR and 3D-QSAR performed by the QSAR-group of Timisoara over a p... more This is a review on studies in QSAR and 3D-QSAR performed by the QSAR-group of Timisoara over a period of more than thirty years. The main interest of our group was the inclusion of molecular stereochemistry in QSAR. The main contributions are the minimal steric difference MSD and the minimal steric topologic difference MTD methods, introducing of new molecular shape descriptors and of new topologic indices. Among them, the MTD method is considered as a precursor of modem 3D-QSAR. The main QSAR applications are also described - the most important QSPR-type studies for dye-cellulose fibre interactions. Contribution to, and especially applications of several modem techniques, such as CoMFA, neural networks, ligand-receptor docking and interactions, classifications in large data bases are also described.
SAR and QSAR in Environmental Research, 2002
This paper presents the application of the MTD (minimal steric difference) analysis and CoMFA (co... more This paper presents the application of the MTD (minimal steric difference) analysis and CoMFA (comparative molecular field analysis) to series of anthraquinone vat, mono and disazo and disperses dyes with known affinities for cellulose fiber. A comparison of the results demonstrates that these methods usually agree with the prediction of structural features favorable for dyeing. A series of n = 49 anthraquinone vat dyes was studied by MTD with r2 between 0.903 and 0.941 and r2CV values in the range of 0.827-0.878. For CoMFA, r2 = 0.992, r2CV = 0.841 were obtained; the CoMFA field is in rather good agreement with vertex attributions, by MTD for attractive and repulsive vertices. Anionic disazo dyes were studied by the CoMFA method (n = 21, r2 = 0.999, r2CV = 0.703). Monoazo dyes (several series) were studied by CoMFA and MTD. The effect of lipophilicity on dye fiber affinity was, also, studied for these dyes. Disperse dye adsorption was analyzed by MTD and CoMFA (n = 27, r2 = 0.925, r2CV = 0.776). Conclusions refer to the effect of structural features of dye molecules upon adsorption on cellulose fibers.
Multilinear and nonlinear QSAR models were built for the skin permeation rate (Log K(p)) of a set... more Multilinear and nonlinear QSAR models were built for the skin permeation rate (Log K(p)) of a set of 143 diverse compounds. Satisfactory models were obtained by three approaches applied: (i) CODESSA PRO, (ii) Neural Network modeling using large pools of theoretical molecular descriptors, and (iii) ISIDA modeling based on fragment descriptors. The predictive abilities of the models were assessed by internal and external validations. The descriptors involved in the equations are discussed from the physicochemical point of view to illuminate the factors that influence skin permeation.
The paper discusses the synthesis and characterization of a tris-azo direct dye containing 4, 4&#... more The paper discusses the synthesis and characterization of a tris-azo direct dye containing 4, 4'-diaminobenzanilide as middle component, and 8-amino-1-naphthol-3, 6-disulfonic acid (H acid) monocoupled with aniline, respectively m-phenylendiamine as coupling components. The synthesized dye was analyzed by means of VIS spectroscopy and thin layer chromatography (TLC). Colouristic and fastness properties of the synthesized dye were also determined. Study of the adsorption isotherms for this dye on cotton fibre was performed at 60°, 86° and 96°. The experimental data obtained from the dyeing process agreed with the standard Nernst, Freundlich and Langmuir isotherms, and with the general multimodal adsorption model, as well. The best statistical results were obtained with the classical Langmuir model. Thermodynamic parameters (equilibrium constants, saturation concentration values) were derived by regression analysis. En ce travail on a presente la synthese et la caracterisation d&#...
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Papers by Ludovic Kurunczi