3D-blast: 3D protein structure alignment, comparison, and classification using spherical polar Fourier correlations

International audienceThis paper presents a novel sequence-independent method of aligning protein structures using three-dimensional spherical polar Fourier (SPF) representations of protein shape. The approach is demonstrated by clustering subsets of the CATH database for each of the four main CATH fold types, and by searching the entire CATH database of some 12,000 structures using several protein structures as queries. Overall, the automatic SPF clustering approach agrees very well with the expert-curated CATH classification, and ROC plot analyses of the database searches show that the approach has very high precision and recall. Database query times can be reduced considerably by using a simple rotationally-invariant pre-filter in tandem with a more sensitive rotational search with little or no reduction in accuracy. Hence it should soon be possible to perform on-line 3D structural searches in interactive time-scales

Using Graphics Processors to Accelerate Protein Docking Calculations

International audienceProtein docking is the computationally intensive task of calculating the three-dimensional structure of a protein complex starting from the individual structures of the constituent proteins. In order to make the calculation tractable, most docking algorithms begin by assuming that the structures to be docked are rigid. This article describes some recent developments we have made to adapt our FFT-based “Hex” rigid-body docking algorithm to exploit the computational power of modern graphics processors (GPUs). The Hex algorithm is very efficient on conventional central processor units (CPUs), yet significant further speed-ups have been obtained by using GPUs. Thus, FFT-based docking calculations which formerly took many hours to complete using CPUs may now be carried out in a matter of seconds using GPUs. The Hex docking program and access to a server version of Hex on a GPU-based compute cluster are both available for public use

HexServer: an FFT-based protein docking server powered by graphics processors

HexServer (http://hexserver.loria.fr/) is the first Fourier transform (FFT)-based protein docking server to be powered by graphics processors. Using two graphics processors simultaneously, a typical 6D docking run takes ∼15 s, which is up to two orders of magnitude faster than conventional FFT-based docking approaches using comparable resolution and scoring functions. The server requires two protein structures in PDB format to be uploaded, and it produces a ranked list of up to 1000 docking predictions. Knowledge of one or both protein binding sites may be used to focus and shorten the calculation when such information is available. The first 20 predictions may be accessed individually, and a single file of all predicted orientations may be downloaded as a compressed multi-model PDB file. The server is publicly available and does not require any registration or identification by the user

PCDDB: new developments at the Protein Circular Dichroism Data Bank

The Protein Circular Dichroism Data Bank (PCDDB) has been in operation for more than 5 years as a public repository for archiving circular dichroism spectroscopic data and associated bioinformatics and experimental metadata. Since its inception, many improvements and new developments have been made in data display, searching algorithms, data formats, data content, auxillary information, and validation techniques, as well as, of course, an increase in the number of holdings. It provides a site (http://pcddb.cryst.bbk.ac.uk) for authors to deposit experimental data as well as detailed information on methods and calculations associated with published work. It also includes links for each entry to bioinformatics databases. The data are freely available to accessors either as single files or as complete data bank downloads. The PCDDB has found broad usage by the structural biology, bioinformatics, analytical and pharmaceutical communities, and has formed the basis for new software and methods developments

Drug Design for CNS Diseases: Polypharmacological Profiling of Compounds Using Cheminformatic, 3D-QSAR and Virtual Screening Methodologies.

HIGHLIGHTS Many CNS targets are being explored for multi-target drug designNew databases and cheminformatic methods enable prediction of primary pharmaceutical target and off-targets of compoundsQSAR, virtual screening and docking methods increase the potential of rational drug design The diverse cerebral mechanisms implicated in Central Nervous System (CNS) diseases together with the heterogeneous and overlapping nature of phenotypes indicated that multitarget strategies may be appropriate for the improved treatment of complex brain diseases. Understanding how the neurotransmitter systems interact is also important in optimizing therapeutic strategies. Pharmacological intervention on one target will often influence another one, such as the well-established serotonin-dopamine interaction or the dopamine-glutamate interaction. It is now accepted that drug action can involve plural targets and that polypharmacological interaction with multiple targets, to address disease in more subtle and effective ways, is a key concept for development of novel drug candidates against complex CNS diseases. A multi-target therapeutic strategy for Alzheimer's disease resulted in the development of very effective Multi-Target Designed Ligands (MTDL) that act on both the cholinergic and monoaminergic systems, and also retard the progression of neurodegeneration by inhibiting amyloid aggregation. Many compounds already in databases have been investigated as ligands for multiple targets in drug-discovery programs. A probabilistic method, the Parzen-Rosenblatt Window approach, was used to build a "predictor" model using data collected from the ChEMBL database. The model can be used to predict both the primary pharmaceutical target and off-targets of a compound based on its structure. Several multi-target ligands were selected for further study, as compounds with possible additional beneficial pharmacological activities. Based on all these findings, it is concluded that multipotent ligands targeting AChE/MAO-A/MAO-B and also D1-R/D2-R/5-HT2A -R/H3-R are promising novel drug candidates with improved efficacy and beneficial neuroleptic and procognitive activities in treatment of Alzheimer's and related neurodegenerative diseases. Structural information for drug targets permits docking and virtual screening and exploration of the molecular determinants of binding, hence facilitating the design of multi-targeted drugs. The crystal structures and models of enzymes of the monoaminergic and cholinergic systems have been used to investigate the structural origins of target selectivity and to identify molecular determinants, in order to design MTDLs

Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution

Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n  =  2 RMP maintaining good confinement ${{H}_{\text{H}\left(98,\text{y}2\right)}}\approx 0.95$ . Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes

Real-time plasma state monitoring and supervisory control on TCV

In ITER and DEMO, various control objectives related to plasma control must be simultaneously achieved by the plasma control system (PCS), in both normal operation as well as off-normal conditions. The PCS must act on off-normal events and deviations from the target scenario, since certain sequences (chains) of events can precede disruptions. It is important that these decisions are made while maintaining a coherent prioritization between the real-time control tasks to ensure high-performance operation. In this paper, a generic architecture for task-based integrated plasma control is proposed. The architecture is characterized by the separation of state estimation, event detection, decisions and task execution among different algorithms, with standardized signal interfaces. Central to the architecture are a plasma state monitor and supervisory controller. In the plasma state monitor, discrete events in the continuous-valued plasma state are modeled using finite state machines. This provides a high-level representation of the plasma state. The supervisory controller coordinates the execution of multiple plasma control tasks by assigning task priorities, based on the finite states of the plasma and the pulse schedule. These algorithms were implemented on the TCV digital control system and integrated with actuator resource management and existing state estimation algorithms and controllers. The plasma state monitor on TCV can track a multitude of plasma events, related to plasma current, rotating and locked neoclassical tearing modes, and position displacements. In TCV experiments on simultaneous control of plasma pressure, safety factor profile and NTMs using electron cyclotron heating (ECH) and current drive (ECCD), the supervisory controller assigns priorities to the relevant control tasks. The tasks are then executed by feedback controllers and actuator allocation management. This work forms a significant step forward in the ongoing integration of control capabilities in experiments on TCV, in support of tokamak reactor operation

High throughput virtual drug screening using spherical harmonic molecular surface representations

This thesis presents new spherical harmonic (SH) approaches for ligand-based high-throughput virtual screening (HTVS). If it is assumed that small drug molecules may be adequately superposed and distinguished by co-locating their centers of mass and by performing rotational correlations of their shapes, then to a good approximation each molecule may be represented very compactly using a two dimensional (2D) SH surface envelope. Of course, this assumes that the true molecular surface is star-like, or single-valued, with respect to radial rays projecting from the selected origin. However, this often holds to a very good approximation for small globular molecules. Even when this is not the case, it is nonetheless reasonable to suppose that similar molecules should give similar radial projections and, therefore, that they should share very similar SH representations. Following this premise, a new program called “SpotLight” was developed. The results obtained with this software show that SH-based global shape matching provides a powerful new way to perform HTVS. SH surface representations are increasingly being applied to a broad range of object recognition and registration tasks, and have also been used to model protein-ligand shape complementarity. Most current shape similarity techniques search for global similarities, and may therefore miss finding active compounds with different overall shapes and sizes but which share similar substructures or surface features. Existing molecular fragment matching algorithms can identify common covalent substructures but they are not well suited for performing scaffold-hopping shape-based database searches. This thesis introduces a novel SH fragment-based shape matching approach that can exploit knowledge of structures of existing protein-ligand complexes to perform virtual screening using as queries SH surface fragments derived from crystallographic ligand binding surfaces.EThOS - Electronic Theses Online ServiceGBUnited Kingdo