4 research outputs found

    The Halogen Bond

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    The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design

    Development of In Silico Tools to Predict the Behavior of Per- and Polyfluoroalkyl Substances (PFAS) in Biological Systems

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    Per and polyfluoroalkyl substances (PFAS) are a group of chemicals that have been widely used in industrial and consumer products for decades. Recent estimates suggest there are over 4000 PFAS on the global market. However, many of these have very little information available about their potential hazards. Given the vast number of PFAS, a three-level hierarchical framework that includes permeability-limited physiologically based toxicokinetic (PBTK) model, molecular dynamics (MD) based workflow and machine learning (ML) based quantitative structure-activity relationships (QSAR) was proposed to inform the toxicokinetics, bioaccumulation and toxicity of PFAS. The PBTK model was developed to estimate the toxicokinetic and tissue distribution of perfluorooctanoic acid (PFOA) in male rats; the hierarchical Bayesian analysis was used to reduce the uncertainty of parameters and improve the robustness of the PBTK model. By comparing with different experimental studies, most of the predicted plasma toxicokinetic (e.g., half-life) and tissue distribution fell well within a factor of 2.0 of the measured data. Moreover, a modeling workflow that combines molecular docking and MD simulation techniques was developed to estimate the binding affinity of PFAS for liver-type fatty acid binding protein (LFABP). The results suggest that EEA and ADONA are at least as strongly bound to rat LFABP as perfluoroheptanoic acid (PFHpA), and to human LFABP as PFOA; both F-53 and F-53B have similar or stronger binding affinities than perfluorooctane sulfonate (PFOS). In addition, human, rat, chicken, and rainbow trout had similar binding affinities to one another for each tested PFAS, whereas Japanese medaka and fathead minnow had significantly weaker LFABP binding affinity for some PFAS. Finally, the ML-based QSAR model was developed to predict the bioactivity of around 4000 PFAS from the OECD report. Based on the collected PFAS dataset, a total of 5 different machine learning models were trained and validated that cover a variety of conventional models (i.e., logistic regression, random forest and multitask neural network) and advanced graph-based models (i.e., graph convolutional network and weave model). The model indicated that most of the biologically active PFAS have perfluoroalkyl chain lengths less than 12 and are categorized into fluorotelomer-related compounds and perfluoroalkyl acids
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