Alex Clark
Research interests
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InterestsCheminformatics, Computational Chemistry, Quantum Chemistry, Drug Design, QSAR
Publications
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3.88Impact points
Accurate specification of molecular structures: the case for zero-order bonds and explicit hydrogen counting.
Journal of chemical information and modeling. 11/2011; 51(12):3149-57.
Most data structures used to represent molecular entities for cheminformatics are underspecified for purposes of representing nonorganic chemical species. Two extensions are proposed: allowing bond orders of 0 and adding an atom property to control the number of inferred attached hydrogen atoms. The... [more] Most data structures used to represent molecular entities for cheminformatics are underspecified for purposes of representing nonorganic chemical species. Two extensions are proposed: allowing bond orders of 0 and adding an atom property to control the number of inferred attached hydrogen atoms. The case for these two extensions is made by demonstrating the effective representation of a number of unconventional bonding types that cannot be effectively represented by data structures currently in common use. A set of enhancements to the industry standard MDL CTfile format is proposed, which includes a backward compatibility mechanism to maximize interpretability by software that has not been updated to make use of the extensions.
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6.63Impact points
Mobile apps for chemistry in the world of drug discovery.
Drug discovery today. 09/2011; 16(21-22):928-39.
Mobile hardware and software technology continues to evolve very rapidly and presents drug discovery scientists with new platforms for accessing data and performing data analysis. Smartphones and tablet computers can now be used to perform many of the operations previously addressed by laptops or de... [more] Mobile hardware and software technology continues to evolve very rapidly and presents drug discovery scientists with new platforms for accessing data and performing data analysis. Smartphones and tablet computers can now be used to perform many of the operations previously addressed by laptops or desktop computers. Although the smaller screen sizes and requirements for touch-screen manipulation can present user-interface design challenges, especially with chemistry-related applications, these limitations are driving innovative solutions. In this early review of the topic, we collectively present our diverse experiences as software developer, chemistry database expert and naïve user, in terms of what mobile platforms could provide to the drug discovery chemist in the way of applications in the future as this disruptive technology takes off.
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Basic primitives for molecular diagram sketching.
Journal of cheminformatics. 10/2010; 2(1):8.
A collection of primitive operations for molecular diagram sketching has been developed. These primitives compose a concise set of operations which can be used to construct publication-quality 2 D coordinates for molecular structures using a bare minimum of input bandwidth. The input requirements fo... [more] A collection of primitive operations for molecular diagram sketching has been developed. These primitives compose a concise set of operations which can be used to construct publication-quality 2 D coordinates for molecular structures using a bare minimum of input bandwidth. The input requirements for each primitive consist of a small number of discrete choices, which means that these primitives can be used to form the basis of a user interface which does not require an accurate pointing device. This is particularly relevant to software designed for contemporary mobile platforms. The reduction of input bandwidth is accomplished by using algorithmic methods for anticipating probable geometries during the sketching process, and by intelligent use of template grafting. The algorithms and their uses are described in detail.
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3.88Impact points
2D depiction of fragment hierarchies.
Journal of chemical information and modeling. 01/2010; 50(1):37-46.
Drug discovery projects often involve organizing compounds in the form of a hierarchical tree, where each node is a substructure fragment shared by all of its descendent nodes. A method is described for producing 2D depiction layout coordinates for each of the nodes in such a tree, ensuring that com... [more] Drug discovery projects often involve organizing compounds in the form of a hierarchical tree, where each node is a substructure fragment shared by all of its descendent nodes. A method is described for producing 2D depiction layout coordinates for each of the nodes in such a tree, ensuring that common fragments within molecular structures are drawn in an identical way, and arranged with a consistent orientation. This is achieved by first deriving a common numbering scheme for common fragments, then using this scheme to redepict each of the molecules, one fragment at a time, so that common fragments have common depiction motifs. Once complete, the distinct root branches can be overlaid onto each other, after which all of the fragments and whole molecules have a common layout and orientation. Several methods are described for preparing visual representations of molecular structure hierarchies alongside activity information. Combining high level tree display and structure depiction showing common features readily facilitates insight into structure-activity relationships.
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4.80Impact points
Detection and Assignment of Common Scaffolds in Project Databases of Lead Molecules.
Journal of medicinal chemistry. 01/2009;
A method is presented for the detection and analysis of multiple common scaffolds for small collections of pharmaceutically relevant molecules that share a set of common structural motifs. The input consists of the molecules themselves, possibly some of the scaffolds, and possibly information about ... [more] A method is presented for the detection and analysis of multiple common scaffolds for small collections of pharmaceutically relevant molecules that share a set of common structural motifs. The input consists of the molecules themselves, possibly some of the scaffolds, and possibly information about the relation between the substitution points of these scaffolds. Three new algorithms are presented: multiple scaffold detection, common scaffold alignment, and scaffold substructure assignment. Each of these steps is relevant for cases when either none, some, or all information about the common scaffolds and their substitution patterns is available. Each of these problems must be solved in an optimal way in order to produce useful structure-activity correlations. The output consists of a collection of scaffolds, a common numbering system, and a unique mapping of each molecule to a single scaffold substructure. This information can then be used to produce data for structure-activity analysis of medicinal chemistry project databases.
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2.17Impact points
Flexible 3D pharmacophores as descriptors of dynamic biological space.
Journal of molecular graphics & modelling. 11/2007; 26(3):622-33.
Development of a pharmacophore hypothesis related to small-molecule activity is pivotal to chemical optimization of a series, since it defines features beneficial or detrimental to activity. Although crystal structures may provide detailed 3D interaction information for one molecule with its recepto... [more] Development of a pharmacophore hypothesis related to small-molecule activity is pivotal to chemical optimization of a series, since it defines features beneficial or detrimental to activity. Although crystal structures may provide detailed 3D interaction information for one molecule with its receptor, docking a different ligand to that model often leads to unreliable results due to protein flexibility. Graham Richards' lab was one of the first groups to utilize "fuzzy" pattern recognition algorithms taken from the field of image processing to solve problems in protein modeling. Thus, descriptor "fuzziness" was partly able to emulate conformational flexibility of the target while simultaneously enhancing the speed of the search. In this work, we extend these developments to a ligand-based method for describing and aligning molecules in flexible chemical space termed FEature POint PharmacophoreS (FEPOPS), which allows exploration of dynamic biological space. We develop a novel, combinatorial algorithm for molecular comparisons and evaluate it using the WOMBAT dataset. The new approach shows superior retrospective virtual screening performance than earlier shape-based or charge-based algorithms. Additionally, we use target prediction to evaluate how FEPOPS alignments match the molecules biological activity by identifying the atoms and features that make the key contributions to overall chemical similarity. Overall, we find that FEPOPS are sufficiently fuzzy and flexible to find not only new ligand scaffolds, but also challenging molecules that occupy different conformational states of dynamic biological space as from induced fits.
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Aryl organometallic compounds of ruthenium and osmium /
Thesis (PhD--Chemistry)--University of Auckland, 1999.
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3.88Impact points
2D depiction of protein-ligand complexes.
Journal of chemical information and modeling. 47(5):1933-44.
A method is presented for the automated preparation of schematic diagrams for protein-ligand complexes, in which the ligand is displayed in conventional 2D form, and the interactions to and between the residues in its vicinity are summarized in a concise and information-rich manner. The structural e... [more] A method is presented for the automated preparation of schematic diagrams for protein-ligand complexes, in which the ligand is displayed in conventional 2D form, and the interactions to and between the residues in its vicinity are summarized in a concise and information-rich manner. The structural entities are arranged to maximize aesthetic ideals and to properly convey important distance relationships. The diagram is annotated with calculated hydrogen bonds, a substitution contour, solvent exposure, chelated metals, covalently bound linkages, pi-pi and pi-cation interactions, and, for series of complexes, conserved residues and interactions. Residues, cofactors, ions, and solvent components are drawn in cartoon form as adjuncts to the ligand. The method can be applied to aligned sets which contain multiple ligands, or multiple members of a protein family, in which case the ligand orientations and protein residue placement will show consistent trends throughout the series.
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3.88Impact points
2D structure depiction.
Journal of chemical information and modeling. 46(3):1107-23.
A comprehensive algorithm for the depiction of 2D coordinates of chemical structures is described. The methods used represent a significant improvement to the state of the art with regard to molecular connection graphs which pose particular difficulty to most layout efforts. Resulting coordinates ar... [more] A comprehensive algorithm for the depiction of 2D coordinates of chemical structures is described. The methods used represent a significant improvement to the state of the art with regard to molecular connection graphs which pose particular difficulty to most layout efforts. Resulting coordinates are consistently of publication quality for a large subset of chemistry. The algorithm is discussed in detail, and measurements of its overall success are presented.
Following (4)
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Antony Williams
The Royal Society of Chemistry -
Sean Ekins
Collaborations in Chemistry -
Melissa Landon
University of Toronto (UofT)
Topics (4)
