Browsing by Author "Duarte, Mariene H."

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    Exploring MIA-QSPR's for the modeling of biomagnification factors of aromatic organochlorine pollutants
    (Ecotoxicology and Environmental Safety, 2017) Mota, Estella G. da; Duarte, Mariene H.; Barigye, Stephen J.; Ramalho, Teodorico C.; Freitas, Matheus P.
    Biomagnification of organic pollutants in food webs has been usually associated to hydrophobicity and other molecular descriptors. However, direct information on atoms and substituent positions in a molecular scaffold that most affect this biological property is not straightforward using traditional QSPR techniques. This work reports the QSPR modeling of biomagnification factors (logBMF) of a series of aromatic organochlorine compounds using three MIA-QSPR (multivariate image analysis applied to QSPR) approaches. The MIA-QSPR model based on augmented molecular images (described with atoms represented as circles with sizes proportional to the respective van der Waals radii and having colors numerically proportional to the Pauling's electronegativity) encoded better the logBMF data. The average results for the main statistical parameters used to attest the model's predictability were r2=0.85, q2=0.72 and r2test=0.85. In addition, chemical insights on substituents and respective positions at the biphenyl rings A and B, and dibenzo-p-dioxin and dibenzofuran motifs are given to aid the design of more ecofriendly derivatives.
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    MIA-plot: a Graphical Tool for Viewing Descriptor Contributions in MIA-QSAR
    (RSC advances, 2016) Barigye, Stephen J.; Duarte, Mariene H.; Nunes, Cleiton A.; Freitas, Matheus P.
    A major challenge faced with the MIA-QSAR (Multivariate Image Analysis applied to Quantitative Structure–Activity Relationships) technique in molecular modeling is to obtain chemically intuitive information from the molecular descriptors that correlate to bioactivity values. This work reports a graphical tool that uses PLS regression coefficients (b) and the variable importance in projection (VIP) scores to give insight on the structural motifs responsible for increased or attenuated biological activities in a congeneric series of compounds. Three sets of compounds useful in food chemistry, namely fatty acids and derivatives (antimicrobial), anilides (antimicrobial) and disaccharides (sweeteners), were used to assess the practical contribution of these parameters in yielding more interpretable models. The MIA-QSAR models demonstrated satisfactory prediction performance and, most importantly, the relevance of single MIA predictors to the response variable could be assessed, thus allowing for the structural, electronic and physicochemical interpretation of the MIA-QSAR models. While VIP-based graphs were especially useful in providing insight on the molecular regions/substituents most affecting the property values, the b-based analysis indicated whether the particular regions/substituents negatively or positively influenced the dependent variables. It is therefore recommended that these parameters be employed as complementary tools for a more robust and lucid model interpretation.