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  • SDEP  (2)
  • 3D-QSAR  (1)
  • diversity searching in databases  (1)
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  • 1
    ISSN: 1573-4951
    Schlagwort(e): AUTODOCK ; COMBINE ; cooked food heterocyclic amines ; cytochrome P450 1A2 ; docking simulation ; GRID/GOLPE ; 3D-QSAR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Many heterocyclic amines (HCA) present in cooked food exert a genotoxic activity when they are metabolised (N-oxidated) by the human cytochrome P450 1A2 (CYP1A2h). In order to rationalize the observed differences in activity of this enzyme on a series of 12 HCA, 3D-QSAR methods were applied on the basis of models of HCA–CYP1A2h complexes. The CYP1A2h enzyme model has been previously reported and was built by homology modeling based on cytochrome P450 BM3. The complexes were automatically generated applying the AUTODOCK software and refined using AMBER. A COMBINE analysis on the complexes identified the most important enzyme–ligand interactions that account for the differences in activity within the series. A GRID/GOLPE analysis was then performed on just the ligands, in the conformations and orientations found in the modeled complexes. The results from both methods were concordant and confirmed the advantages of incorporating structural information from series of ligand–receptor complexes into 3D-QSAR methodologies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of computer aided molecular design 12 (1998), S. 573-581 
    ISSN: 1573-4951
    Schlagwort(e): calculation procedures ; diversity searching in databases ; linear regression ; octanol/water partitioning (log Poct) ; principal component analysis ; reversed-phase thin-layer chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Two experimental (log P, RMw) and 17 calculation descriptors for molecular lipophilicity (fragmental, atom-based or based on molecular properties) were investigated by multivariate analysis for a database of 159 compounds including both simple structures as well as more complex drug molecules. Principal component analysis (PCA) of the entire database exhibits a clustering of chemical groups; preciseness of clustering corresponds to chemical similarity. Thus, diversity searching in databases might effectively be performed by PCA on the basis of calculated log P. The comparative validity check of experimental and computational procedures by regression analysis and PCA was performed with a chemically balanced, reduced data set (n=55) representing 11 chemical groups with 5 members each. Regression of experimental descriptors (log Poct versus RMw) proves that chromatographic data, obtained under well-defined experimental conditions, can be used as valid substitutes for log P. Regression of calculated versus experimental lipophilicity data shows a superiority of fragmental over atom-based methods and approaches based on molecular properties, as indicated by correlation coefficients, slopes and intercepts. In addition, PCA revealed that fragmental methods (Rekker-type, KOWWIN, KLOGP) sense the compound ranking in log P data to almost the same extent as experimental approaches. For atom-based procedures and CLOGP, both the comparability of absolute values and the sensing of the compound ranking in the database are slightly less. This trend is more pronounced for the methods based on molecular properties, with the exception of BLOGP.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 0886-9383
    Schlagwort(e): GOLPE ; PLS ; Regression ; SDEP ; Variable selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A procedure called GOLPE is suggested in order to detect those variables which increase the predictivity of PLS models. The procedure is based on evaluating the predictive power of a number of PLS models built by different combinations of variables selected according to a factorial design strategy. Examples are given of the efficiency of this variable selection procedure, which shows how these predictive PLS models are better than those obtained by all variables and better than the corresponding ordinary regression models.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 0886-9383
    Schlagwort(e): Predictive ability ; Regression ; PLS ; SDEP ; Cross-validation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The standard deviation of prediction errors (SDEP) is used to evaluate and compare the predictive ability of some regression models, namely MLR, ACE and linear and non-linear PLS, the last being the best one. The parameter is determined by a cross-validation approach as an average of several runs obtained on forming groups in a random way. The variation in SDEP with the number of latent variables in PLS is also discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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