Whilst high-throughput screening (HTS) has been the starting point for many successful drug discovery programs the cost of screening, the lack of access to a large diverse sample collection, or the low throughput of the primary assay may preclude HTS as a starting point and identification of a smaller selection of compounds with a higher probability of being a hit may be desired. Directed or Virtual screening is a computational technique used in drug discovery research designed to identify potential hits for evaluation in primary assays. It involves the rapid in silico assessment of large libraries of chemical structures in order to identify those structures that most likely to be active against a drug target. The in silico screen can be based on known ligand similarity or based on docking ligands into the desired binding site.
I've updated the description to give more information about preparing the target protein.
Chemical Computing Group are running a free hands-on workshops on Structure-Based Drug Design
CAMBRIDGE – December 1, 2016 St John's Innovation Centre Cowley Road, Cambridge, Cambridgeshire, CB4 0WS, UK
09:00-12:30 Structure-Based Drug Design and Ligand Modification Molecular Surfaces and Maps / Ligand Interactions / Conformational Searching / Ligand Optimization / Ligand Selectivity / Protein Alignements and Superposition
12:30-13:30 Lunch break*
13:30-17:00 Advanced Structure-Based Drug Design Pharmacophore Modeling / Docking / Fragment-based Design / Scaffold Replacement / R-Group Screening / Project Search / Protein-Ligand Interaction
Note: Computers will be provided. No prior software experience required.
*Lunch and refreshments will be provided.
I've been making increasing use of iPython notebooks, both as a way to perform calculations but also as a way of cataloging the work that I've been doing. One thing I seem to be doing quite regularly is calculating physicochemical properties for libraries of compounds and then creating a trellis of plots to show each of the calculated properties. In the past I've done this with a series of applescripts using several applications. This seemed an ideal task to try out using an iPython notebook.
Chemical Computing Group have just released an up date to MOE, version 2015.10 includes:-
- Generate docked poses using FFT followed by all atom minimization
- Define receptor and ligand sites to focus docking
- Automatically detect antibody CDR sites
Integrated Alignment, Consensus and Superposition in the Sequence Editor
- Manipulate multimeric protein sequences using split side-by-side Sequence Editor panes
- Use dendrograms to visualize pairwise similarity, identity and RMSD relationships
- Select residues based on plotted values using resizable sequence editor plots
Distributed Pharmacophore Searching
- Run pharmacophore searches on a cluster directly from MOE GUI
- Perform fast corporate database searches
- Access multiple databases stored on a central server
Covalent Docking and Electron Density Docking
- Use reaction-based organic transformations to covalently docking
- Minimize ligand strain energy while maximizing ligand fit to electron density
- Run docking through an enhanced streamlined scenario-based interface
Extended Hückel Descriptors and pKa Model
- Compute molecular properties such as logP, logS and molar refractivity
- Determine populations of ligand protonation states at a given pH
- Calculate the pKa and pKb of small molecules
13C NMR Analysis
- Apply QM conformation refinement to calculate 13C NMR shielding
- Convert computed shieldings and predict 13C NMR chemical shifts
- Compare computed chemical shifts to experimental shifts for structure determination
I'll write a review in the New Year.
In the tutorial Scripting Vortex 15 I showed how it is possible to create a contextual script for Vortex that downloaded a specific PDB file, then a FlexAlign Vortex script first identifies the structure column and then get the SMILES string of the selected molecule generates a 3D structure and uses Flex Align to do a one-shot flexalign between the ligand in the system in MOE, and the incoming ligand.
While this is useful if you have similar structures (perhaps analogues in a series) there will certainly be situations where it may be preferable to dock the new ligand into the binding site. The Scripting Vortex 17 tutorial describes how to achieve this.
Chemical Computing Group have just announced the release of the latest update of MOE (Molecular Operating Environment).
Extended Hückel Theory for Pharmacophore Discovery
- Apply EHT strengths to identify and discover weak and strong interactions
- Annotate non-standard interactions: halogen and CH bond donors
- Score pharmacophore hits using sum of interaction energies
de novo Loop and Linker Modeler
- Search and browse for de novo and knowledge-based loop candidates
- Generate multiple loop conformations and score loop-loop interactions • Investigate linkers for fusion proteins and dual variable domains
Protein Alignments and Superpositions
- Superpose protein structures independent of sequence
- Apply new threading methodology for sequence to structure alignments
- Align sequences and superpose structures using STOVCA criteria
Core System Enhancements (with 64-bit support) The default versions of MOE for Linux, Windows, and Mac OSX are now all 64-bit. The current release also includes 32-bit versions for each architecture.
- Create additional data grouping level in System Manager
- Handle large number of protein:ligand complexes in real-time
- Colour database viewer text and cells by data values for enhanced analysis, Empty cells can be specially colored
Interface to Mogul from CCDC
- Access a knowledge-based library of small molecule crystallographic data
- Visualize histograms and statistics fo rbond angles, dihedrals and torsions • Ensure ligand conformation is consistent with the CSD
Solvent Analysis using 3D-RISM Enhancements
- Calculate water densities on full protein or protein:protein interface
- Accurate placement and stability prediction of water sites
- Use3 D-RISM densities to validate water position in crystal structures
chEMBL Library. MOE's SD Pipeline Command Tools were used to generate fragments from Release 14 of the ChEMBL database of bioactive drug-like small molecules. The resulting database of conformations, chemblr14_frag.mdb, for approximately 830,000 fragments, suitable for Scaffold Replacement or combinatorial chemistry methodologies
Mac OS X Enhancements.
OS X Dock Icon Enhancements. A new Dock menu, accessed by right-clicking (or control-clicking) the MOE Dock icon, allows for standard Mac OS X operations – Hide, Show, and Quit – across all open iterations of MOE. The Dock Menu also contains menu items in order for users to view the About panel bundled in MOE, as well as access the Preferences panel. Additionally, the Dock indicator light under the MOE Dock icon remains persistent after having launched a new instance of MOE, until all opened MOE instances have been closed. Users continue to be able to drag and drop compatible MOE documents (i.e. .pdb, .svl, etc.) onto the Desktop and/or Dock icons for direct opening in MOE.
New Preferences Menu. A new Preferences panel allows for certain parameters to be set and/or changed graphically. These parameters include the defaults key and path to MOE, the current configuration of MOE (32- or 64-bit, or Auto-select), as well as a selection of common command line tags, with a custom section for inputting other command line options.
Output Continuity. stdout and stderr received from MOE have been standardized to be displayed in a native panel in a scrollable text box.
One of the new features in the latest version of MOE from Chemical Computing Group is the Listener. The MOE socket listener provides an alternative to MOE/web for executing functions remotely on a running instance of MOE.
The script will download the associated PDB structures from the rcsb Protein Data Bank, put them into a database then start the browser. It may take a few seconds to download the structure; this does rely on MOE having the right proxy settings to access the internet (use the Java console to set them). You can now transfer this to MOE and amend the display to highlight the ligand.
The MOEflexalign script takes the SMILES string of the selected row generates a 3D structure and does a one-shot flexalign between the ligand in the system in MOE, and the incoming ligand.
It is probably easier to see this in action, if it appears rather small click on the YouTube icon in the bottom right corner of the video.
In tutorial 4 we looked at using the command line tool sddesc from Chemical Computing Group to calculate a number of molecular descriptors and then import them into Vortex. However there a couple of issues with doing this not the least ensuring all the environment variables are set correctly. An alternative is to use MOE as a web service and access the tools using the SOAP protocol (Simple Object Access Protocol). This protocol provides a specification for exchanging structured information in the implementation of Web Services in computer networks. It relies on XML Information Set for its message format.