Biomedical subjects

L Kurunczi

Publications and source records attributed to L Kurunczi.

4 recordsLinked to original sources

PubMed2002

Steric and electrostatic effects in dye-cellulose interactions by the MTD and CoMFA approaches.

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.

Adsorption↗

PubMed2001

Correlation of aerobic biodegradability of sulfonated azo dyes with the chemical structure.

The reported data of biodegradability of variously substituted 25 sulfonated azo dyes were divided into two classes: 8 dyes designated "rapidly biodegradable" and 17 dyes "not rapidly biodegradable", by applying principal components analysis (PCA). The biodegradability of the dyes was modeled with the discriminant technique of two-value regression analysis based on structural descriptors. A statistically significant and biologically meaningful regression model that gives perfect classification was obtained, and the results were compared with the previous qualitative interpretation of the substituent effects on biodegradation. The coefficients of the regression model revealed a significant interaction between ring substituents for biodegradability. The results facilitate understanding of the mechanism of degradation.

Azo Compounds↗

PubMed2001

MTD-PLS: a PLS-based variant of the MTD method. A 3D-QSAR analysis of receptor affinities for a series of halogenated dibenzoxin and biphenyl derivatives.

MTD-PLS, the Partial Least Squares (PLS) variant of the Minimum Topological Difference (MTD) method is described. In MTD-PLS, molecules are characterised not only by the occupancy or nonoccupancy of the hypermolecular vertices (as in classical MTD), but also by additional descriptors for each vertex: fragmental van der Waals volumes, fragmental hydrophobicities, partial atomic charges, etc. This method was applied to a series of 73 polyhalogenated derivatives of dibenzo-p-dioxine, dibenzofuran and biphenyl (induction of aryl hydrocarbon hydrolase and affinities to rat cytosolic receptor), previously studied by MTD. The separation of steric, hydrophobic, and electrostatic effects was achieved retranslating from the latent variable space into a linear combination of the initial structural variables. The MTD-PLS method yields more detailed results compared to classical MTD, indicating the importance of electrostatic effects at some substituent positions.

Binding Sites↗

PubMed1998

MTD-ADJ: a multiconformational minimal topologic difference for determining bioactive conformers using adjusted biological activities.

The active conformation is part of a conformational mixture with experimental activity Yexp, and is used in QSAR studies to extract more information regarding the ligand-receptor interaction. To reflect the relative amount (alpha) of the active conformation, we adjust Yexp: Yadj = Yexp - log alpha. We establish a quantitative structure-activity relationship (QSAR) between Yadj and 3D conformational characteristics for the acetylcholinesterase (AChE) hydrolysis rates of 25 acetic esters. The 3D-QSAR model was obtained using the adjusted multiconformational minimal steric/topologic difference (MTD-ADJ) method, optimizing the receptor map based on Yadj for each conformer. Yadj was updated during each step of the optimization process. alpha and Yadj are based on the Boltzmann distribution calculated using AMI (MOPAC 6.0) relative energies of the COSMIC 90 derived conformers. The MTD-ADJ results are: (i) the 3D-QSAR models obtained by this procedure have significant statistical parameters and are similar to the unadjusted (MTD-MC, using Yexp) models; (ii) the selected bioactive conformations are extended, occupy cavity vertices and, for the same structures, have the same MTD value; and (iii) the optimized conformational map of the neutral ligands obtained from the MTD-ADJ model fits well in the active site of the crystallographic structure of AChE (from Torpedo californica). We propose a neutral ligands binding site model for AChE. Our results show that MTD-ADJ, which can be implemented in any 3D-QSAR method, is capable of providing additional information regarding the active conformations, and can be used to gain further insight into the ligand-receptor models for which no structural data are available.

Acetylcholinesterase↗