27. Cook’s Unified Pharmacophore Figure III . The pyrazolo [3,4-c]quinolin-3-one ligand CGS-9896 (dotted line), diazepam (thick line), and planar diindoles (thin line) fitted to a schematic representation of the inclusive pharmacophore model for the BzR. The descriptors H1 and H2 designate hydrogen bond donor sites on the receptor protein while A2 represents a hydrogen bond acceptor site necessary for potent inverse agonist activity in vivo . L1, L2, L3 and LDi are four lipophilic regions in the binding
29. Classes of Ligands Employed for the Study of Pharmacophore/ Receptor Models of BzR Subtypes
30.
31. Overlay of Included Volume of Pharmacophore/Receptor Model for and Receptor Subtypes Orthogonal views of the overlap of the included volumes of the pharmacophore/ receptor models for a1b3g2 (green) and a5b3g2 (red) receptor subtypes(overlap in yellow).
32. L 2 L 2 A 1 A 1 H 1 H 2 H 2 H 1 L Di L Di L 3 L 3 L 1 L 1 L 2 L 2 A 1 A 1 H 1 H 2 H 2 H 1 L Di L Di L 3 L 3 L 1 L 1 L 2 L 2 A 1 A 1 H 1 H 2 H 2 H 1 L Di L Di L 3 L 3 L 1 L 1 L 2 L 2 A 1 A 1 H 1 H 2 H 2 H 1 L Di L Di L 3 L 3 L 1 L 1 L 2 L 2 A 1 A 1 H 1 H 2 H 2 H 1 L Di L Di L 3 L 3 L 1 L 1 ) Orthogonal views of the overlap (yellow) volumes of a1b3g2 (red) and a2b3g2 (green) b) Orthogonal views of the overlap (yellow) volumes of a2b3g2 (red) and a3b3g2 (green) c) Orthogonal views of the overlap (yellow) volumes of a4b3g2 (red) and a6b3g2 (green) d) Orthogonal views of the overlap (yellow) volumes of a1b3g2 (red) and a6b3g2 (green) e) Orthogonal views of the overlap (yellow) volumes of a5b3g2 (red) and a1b3g2 (green) f) Diazepam and the unified pharmacophore descriptors depicted in the included volume of the a1b3g2 subtype.
33. The 8-Phenyl Ligands Aligned in the Included Volume of the Pharmacophore/Receptor Model for the (blue) and (red) Subtypes
42. Cross-section of GABA A Receptor Absolute subunit arrangement of the a1b2g2 GABAA receptor when viewed from the synaptic cleft. The GABA binding sites are located at the b+a- subunit interfaces and the modulatory Bz BS (Bz) is located at the a+g- subunit interface.18, [i] [i] Pritchett, D., Sontheimer, H., Shivers, B., Ymer, S., Kettenmann, H., Schofield, P., and Seeburg, P., Importance of a novel GABAA receptor subunit for benzodiazepine pharmacology, Nature , 1989 , 338, 582-585.
Homology modeling , also known as comparative modeling of protein refers to constructing an atomic-resolution model of the " target " protein from its amino acid sequence and an experimental three-dimensional structure of a related homologous protein (the " template ").
Pyridodiindoles- note the loss in binding when R7 is methyl Phenylpyrazoloquinolinones
3 substituted ethers
International Union of Pure and Applied Chemistry
Here we are studying how betacarbolines fit in the lipopohilic pocket. The excluded receptor volume was generated by using the MVOL option of SYBYL 5.22 by subtracting the union of the volume of the “actives” from the union of volume of the “inactives”.
Introduced 2 descriptors in in 1992. Places the hydrogen bond donor 1.84 A away from Nitrogen and A2 1.84 A away from the indole proton Inverse agonist bccm
Antagonist- the earliest fit of a benzo in the developing pharmacophore with an imidazo Nitrogen coordinating with ideal bond lengths at 1.84 A and the carbonyl lone pair adjusted to 135 degrees from ( 120)
basis set in chemistry is a set of functions used to create the molecular orbitals
Monte Carlo Methods and the Metropolis Criterion Other search methods can be much more efficient for sampling conformational space and determining low-energy structures of a protein, such as stochastic searches involving "importance sampling": Start from an initial conformation, and minimize this structure with respect to the energy. Choose an arbitrary number of torsional angles from the initial conformation, vary them by a random amount, and then minimize this conformation. Use a criterion based on the energy to retain or discard this move (see below). If retained, continue; if discarded, go back to step 1. Compare the resulting structure against all structures previously found. If it does not match any of them, then store this structure as a unique one. Return to Step 2 and continue. Stop the search procedure when no new structures are found. Monte Carlo (MC) and Molecular Dynamics (MD) or Stochastic Dynamics (SD) use distinct methods to generate conformational states. In MC changes are assigned to the system by randomly modifying a few degrees of freedom at a time; the atoms are moved truly randomly, not deterministically. This methods allows for significant thermal fluctuations and sampling of higher energy structures, thus producing a wide spectrum of conformational states economicaly.
Scf=tight- rigorous algorithm to a achieve identical population of low energy minimizations. Scf-qc is a less rigorour algorithm used in larger proteins that “ fail to converge”
PLS IS USEFUL IN MULTIVARIATE SYSTEMS.
BCCM (I), pyridodiindole 3, and 3H-2- phenyl-2,5-dihydropyrazolo[4,3-clquinolin-3-on(e4 1). Red and yellow contours surround regions where a more negative electlostatic interaction is predicted to increase dfinity
Red – do not want steric interaction. Green/yellow- steric interaction is good
Note the CoMFA does not show that negative electrostatic at carbonyl enhances affinity..This is because all ligands used in the comfa were of this scaffold. YOU CANT SEE DIFFERENCES IF YOUR DATASET IS ALL THE SAME.
pyrazoloquinoline ligand CGS-8216 , Diazepam 8-carbolines which effect agonist actions (i. ZK-93423, H1 and H2 are hydrogen bond donating groups indicated by the arrows in the left (yellow) and right (orange) hand portions, respectively. L2 and L3 are areas of lipophilic interaction indicated by the arrows on the top right (redorange) and left (cyan), respectively. S1 and S2 are areas of negative interaction shown in purple.
Here we are studying how betacarbolines fit in the lipopohilic pocket. The excluded receptor volume was generated by using the MVOL option of SYBYL 5.22 by subtracting the union of the volume of the “actives” from the union of volume of the “inactives”.
Using 166 ligands from 9 different families a binding site was proposed and included volumes were build using ligands with had good binding affinities.
Figure 6: Overlap between pairs of included volumes derived from receptor subtype selective ligands: a) a1 and a2 , b) a2 and a3 , c) a4 and a6 , d) a1 and a6, e) a1 and a5 . Yellow color indicates overlapping regions and each grid measures 4 Å in width and height. In order to provide the connection between this figure and other figures, f) shows diazepam and the descriptors of the unified pharmacophore model depicted in the included volume requirement of the a1 subtype.
8-substituted
2.74 kcal/mol higher energy in syn conformation of ester for Ro-4513 ( N=N=N at 8 position , ethyl ester , CO at 5) WHAT IS ENERGY DIFFERENCE IN RING A VERSUS B
A2/a3 selective ligands aligned Perform a receptor surface analysis 3D QSAR
serotonin–norepinephrine–dopamine reuptake inhibitor Coding of features: blue sphere, positive ionizable; pink spheres, H-bond acceptor; green spheres, hydrophobic; orange sphere, aromatic….maestro created 3 pharmacophore….merged to one. For the triple reuptake inhibitors. Blockade of hERG K + channels is widely regarded as the predominant cause of Cardiac arrhythmia …. data for a diverse set of 194 potent uncharged hERG actives, we propose a pharmacophore for neutral hERG blockers …..used as a screen…. Pharmacophores for Uncharged Human Ether-a-go-go-Related Gene (hERG) Blockers ring…MOE used to build multiple pharmacophores….then the best pharmacophores with fewest (5) green (hydrophobe/aromatic) and red (hydrogen bond acceptor)
Homology modeling , also known as comparative modeling of protein refers to constructing an atomic-resolution model of the " target " protein from its amino acid sequence and an experimental three-dimensional structure of a related homologous protein (the " template ").
site directed mutagenesis studies have led to the conclusion that the GABA receptor is between an alpha and beta subunit and the Bz receptor is lied between an alpha and gamma subunit. This has made it difficult to crystalize this pentameric protein complex.
Brejc in 2001 reports the crystal structure of homopentamer with a ligand in the binding site. This was verified as the residues implicated with agonist binding in nAChR and AChBP were conserved in the receptor. [site directed mutagenesis]
Crystal structure of a single alpha subunit of the acetylcholine binding protein.. This was verified as the residues implicated with agonist binding in nAChR and AChBP were conserved in the receptor. [site directed mutagenesis]
. The ligand binding domains of human GABA A receptors (a1, a2, a3, a5, b2, and g2) were obtained from the Research Collaboratory for Structural Bioinformatics (RCSB). Originated in 1971 at Brookhaven National Laboratories, this is the home of the Protein Data Bank.
Thread amino acid using iterative magic fit.
dihedral angles ψ against φ of amino acid residues in protein structure . [1] It shows the possible conformations of ψ and φ angles for a polypeptide . Root mean square deviation
Could our compounds be racemic? H NMR or HPLC to elucidate…DONE BY NMR