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Wickstrom L, Gallicchio E, Chen L, Kurtzman T, Deng N. Developing end-point methods for absolute binding free energy calculation using the Boltzmann-quasiharmonic model. Phys Chem Chem Phys 2022; 24:6037-6052. [PMID: 35212338 PMCID: PMC9044818 DOI: 10.1039/d1cp05075c] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Understanding the physical forces underlying receptor-ligand binding requires robust methods for analyzing the binding thermodynamics. In end-point binding free energy methods the binding free energy is naturally decomposable into physically intuitive contributions such as the solvation free energy and configurational entropy that can provide insights. Here we present a new end-point method called EE-BQH (Effective Energy-Boltzmann-Quasiharmonic) which combines the Boltzmann-Quasiharmonic model for configurational entropy with different solvation free energy methods, such as the continuum solvent PBSA model and the integral equation-based 3D-RISM, to estimate the absolute binding free energy. We compare EE-BQH with other treatments of configurational entropy such as Quasiharmonic models in internal coordinates (QHIC) and in Cartesian coordinates (QHCC), and Normal Mode analysis (NMA), by testing them on the octa acids host-guest complexes from the SAMPL8 blind challenge. The accuracies in the calculated absolute binding free energies strongly depend on the configurational entropy and solvation free energy methods used. QHIC and BQH yield the best agreements with the established potential of mean force (PMF) estimates, with R2 of ∼0.7 and mean unsigned error of ∼1.7 kcal mol-1. These results from the end-point calculations are also in similar agreement with experiments. While 3D-RISM in combination with QHIC or BQH lead to reasonable correlations with the PMF results and experiments, the calculated absolute binding free energies are underestimated by ∼5 kcal mol-1. While the binding is accompanied by a significant reduction in the ligand translational/rotational entropy, the change in the torsional entropy in these host-guest systems is slightly positive. Compared with BQH, QHIC underestimates the reduction of configurational entropy because of the non-Gaussian probability distributions in the ligand rotation and a small number of torsions. The study highlights the crucial role of configurational entropy in determining binding and demonstrates the potential of using the new end-point method to provide insights in more complex protein-ligand systems.
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Affiliation(s)
- Lauren Wickstrom
- Borough of Manhattan Community College, The City University of New York, Department of Science, New York, New York, USA
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, New York, USA.,PhD Program in Chemistry, Graduate Center of the City University of New York, New York, USA.,PhD Program in Biochemistry, Graduate Center of the City University of New York, New York, USA
| | - Lieyang Chen
- PhD Program in Chemistry, Graduate Center of the City University of New York, New York, USA.,PhD Program in Biochemistry, Graduate Center of the City University of New York, New York, USA.,Department of Chemistry, Lehman College, The City University of New York, Bronx, New York, USA
| | - Tom Kurtzman
- PhD Program in Chemistry, Graduate Center of the City University of New York, New York, USA.,PhD Program in Biochemistry, Graduate Center of the City University of New York, New York, USA.,Department of Chemistry, Lehman College, The City University of New York, Bronx, New York, USA
| | - Nanjie Deng
- Department of Chemistry and Physical Sciences, Pace University, New York, New York, USA.
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2
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Chen L, Cruz A, Roe DR, Simmonett AC, Wickstrom L, Deng N, Kurtzman T. Thermodynamic Decomposition of Solvation Free Energies with Particle Mesh Ewald and Long-Range Lennard-Jones Interactions in Grid Inhomogeneous Solvation Theory. J Chem Theory Comput 2021; 17:2714-2724. [PMID: 33830762 DOI: 10.1021/acs.jctc.0c01185] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Grid Inhomogeneous Solvation Theory (GIST) maps out solvation thermodynamic properties on a fine meshed grid and provides a statistical mechanical formalism for thermodynamic end-state calculations. However, differences in how long-range nonbonded interactions are calculated in molecular dynamics engines and in the current implementation of GIST have prevented precise comparisons between free energies estimated using GIST and those from other free energy methods such as thermodynamic integration (TI). Here, we address this by presenting PME-GIST, a formalism by which particle mesh Ewald (PME)-based electrostatic energies and long-range Lennard-Jones (LJ) energies are decomposed and assigned to individual atoms and the corresponding voxels they occupy in a manner consistent with the GIST approach. PME-GIST yields potential energy calculations that are precisely consistent with modern simulation engines and performs these calculations at a dramatically faster speed than prior implementations. Here, we apply PME-GIST end-state analyses to 32 small molecules whose solvation free energies are close to evenly distributed from 2 kcal/mol to -17 kcal/mol and obtain solvation energies consistent with TI calculations (R2 = 0.99, mean unsigned difference 0.8 kcal/mol). We also estimate the entropy contribution from the second and higher order entropy terms that are truncated in GIST by the differences between entropies calculated in TI and GIST. With a simple correction for the high order entropy terms, PME-GIST obtains solvation free energies that are highly consistent with TI calculations (R2 = 0.99, mean unsigned difference = 0.4 kcal/mol) and experimental results (R2 = 0.88, mean unsigned difference = 1.4 kcal/mol). The precision of PME-GIST also enables us to show that the solvation free energy of small hydrophobic and hydrophilic molecules can be largely understood based on perturbations of the solvent in a region extending a few solvation shells from the solute. We have integrated PME-GIST into the open-source molecular dynamics analysis software CPPTRAJ.
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Affiliation(s)
- Lieyang Chen
- Department of Chemistry, Lehman College, The City University of New York, 250 Bedford Park Boulevard West, Bronx, New York 10468, United States.,Ph.D. Program in Biochemistry, The Graduate Center of The City University of New York, New York, New York 10016, United States
| | - Anthony Cruz
- Department of Chemistry, Lehman College, The City University of New York, 250 Bedford Park Boulevard West, Bronx, New York 10468, United States.,Ph.D. Program in Chemistry, The Graduate Center of The City University of New York, New York, New York 10016, United States
| | - Daniel R Roe
- Laboratory of Computational Biology, National Institutes of Health - National Heart, Lung and Blood Institute, Bethesda, Maryland 20892, United States
| | - Andrew C Simmonett
- Laboratory of Computational Biology, National Institutes of Health - National Heart, Lung and Blood Institute, Bethesda, Maryland 20892, United States
| | - Lauren Wickstrom
- Department of Science, Borough of Manhattan Community College, The City University of New York, New York, New York 10007, United States
| | - Nanjie Deng
- Department of Chemistry and Physical Sciences, Pace University, New York, New York 10038, United States
| | - Tom Kurtzman
- Department of Chemistry, Lehman College, The City University of New York, 250 Bedford Park Boulevard West, Bronx, New York 10468, United States.,Ph.D. Program in Biochemistry, The Graduate Center of The City University of New York, New York, New York 10016, United States.,Ph.D. Program in Chemistry, The Graduate Center of The City University of New York, New York, New York 10016, United States
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3
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Tse C, Wickstrom L, Kvaratskhelia M, Gallicchio E, Levy R, Deng N. Exploring the Free-Energy Landscape and Thermodynamics of Protein-Protein Association. Biophys J 2020; 119:1226-1238. [PMID: 32877664 DOI: 10.1016/j.bpj.2020.08.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 08/04/2020] [Accepted: 08/06/2020] [Indexed: 01/30/2023] Open
Abstract
We report the free-energy landscape and thermodynamics of the protein-protein association responsible for the drug-induced multimerization of HIV-1 integrase (IN). Allosteric HIV-1 integrase inhibitors promote aberrant IN multimerization by bridging IN-IN intermolecular interactions. However, the thermodynamic driving forces and kinetics of the multimerization remain largely unknown. Here, we explore the early steps in the IN multimerization by using umbrella sampling and unbiased molecular dynamics simulations in explicit solvent. In direct simulations, the two initially separated dimers spontaneously associate to form near-native complexes that resemble the crystal structure of the aberrant tetramer. Most strikingly, the effective interaction of the protein-protein association is very short-ranged: the two dimers associate rapidly within tens of nanoseconds when their binding surfaces are separated by d ≤ 4.3 Å (less than two water diameters). Beyond this distance, the oligomerization kinetics appears to be diffusion controlled with a much longer association time. The free-energy profile also captured the crucial role of allosteric IN inhibitors in promoting multimerization and explained why several C-terminal domain mutations are remarkably resistant to the drug-induced multimerization. The results also show that at small separation, the protein-protein binding process contains two consecutive phases with distinct thermodynamic signatures. First, interprotein water molecules are expelled to the bulk, resulting in a small increase in entropy, as the solvent entropy gain from the water release is nearly cancelled by the loss of side-chain entropies as the two proteins approach each other. At shorter distances, the two dry binding surfaces adapt to each other to optimize their interaction energy at the expense of further protein configurational entropy loss. Although the binding interfaces feature clusters of hydrophobic residues, overall, the protein-protein association in this system is driven by enthalpy and opposed by entropy.
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Affiliation(s)
- Celine Tse
- Department of Chemistry and Physical Sciences, Pace University, New York, New York
| | - Lauren Wickstrom
- Borough of Manhattan Community College, the City University of New York, Department of Science, New York, New York
| | - Mamuka Kvaratskhelia
- Division of Infectious Diseases, University of Colorado School of Medicine, Aurora, Colorado
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, the City University of New York, Brooklyn, New York; PhD Program in Biochemistry and PhD Program in Chemistry, The Graduate Center of the City University of New York, New York, New York
| | - Ronald Levy
- Center for Biophysics and Computational Biology and Department of Chemistry, Temple University, Philadelphia, Pennsylvania
| | - Nanjie Deng
- Department of Chemistry and Physical Sciences, Pace University, New York, New York.
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4
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Cruz J, Wickstrom L, Yang D, Gallicchio E, Deng N. Combining Alchemical Transformation with a Physical Pathway to Accelerate Absolute Binding Free Energy Calculations of Charged Ligands to Enclosed Binding Sites. J Chem Theory Comput 2020; 16:2803-2813. [PMID: 32101691 DOI: 10.1021/acs.jctc.9b01119] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We present a new approach to more accurately and efficiently compute the absolute binding free energy for receptor-ligand complexes. Currently, the double decoupling method (DDM) and the potential of mean force method (PMF) are widely used to compute the absolute binding free energy of biomolecular complexes. DDM relies on alchemically decoupling the ligand from its environments, which can be computationally challenging for large ligands and charged ligands because of the large magnitude of the decoupling free energies involved. In contrast, the PMF method uses a physical pathway to directly transfer the ligand from solution to the receptor binding pocket and thus avoids some of the aforementioned problems in DDM. However, the PMF method has its own drawbacks: because of its reliance on a ligand binding/unbinding pathway that is free of steric obstructions from the receptor atoms, the method has difficulty treating ligands with buried atoms. To overcome the limitation in the standard PMF approach and enable buried ligands to be treated, here we develop a new method called AlchemPMF in which steric obstructions along the physical pathway for binding are alchemically removed. We have tested the new approach on two important drug targets involving charged ligands. One is HIV-1 integrase bound to an allosteric inhibitor; the other is the human telomeric DNA G-quadruplex in complex with a natural product protoberberine buried in the binding pocket. For both systems, the new approach leads to more reliable estimates of absolute binding free energies with smaller error bars and closer agreements with experiments compared with those obtained from the existing methods, demonstrating the effectiveness of the new method in overcoming the hysteresis often encountered in PMF binding free energy calculations of such systems. The new approach could also be used to improve the sampling of water equilibration and resolvation of the binding pocket as the ligand is extracted.
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Affiliation(s)
- Jeffrey Cruz
- Department of Chemistry and Physical Sciences, Pace University, New York, New York 10038, United States
| | - Lauren Wickstrom
- Department of Science, Borough of Manhattan Community College, The City University of New York, New York, New York 10007, United States
| | - Danzhou Yang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, Indiana 47907, United States
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, New York 11210, United States.,Ph.D. Program in Biochemistry, Graduate Center, City University of New York, New York, New York 10016, United States.,Ph.D. Program in Chemistry, Graduate Center, City University of New York, New York, New York 10016, United States
| | - Nanjie Deng
- Department of Chemistry and Physical Sciences, Pace University, New York, New York 10038, United States
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5
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He P, Sarkar S, Gallicchio E, Kurtzman T, Wickstrom L. Role of Displacing Confined Solvent in the Conformational Equilibrium of β-Cyclodextrin. J Phys Chem B 2019; 123:8378-8386. [PMID: 31509409 DOI: 10.1021/acs.jpcb.9b07028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This study investigates the role of hydration and its relationship to the conformational equilibrium of the host molecule β-cyclodextrin. Molecular dynamics simulations indicate that the unbound β-cyclodextrin exhibits two state behavior in explicit solvent due to the opening and closing of its cavity. In implicit solvent, these transitions are not observed, and there is one dominant conformation of β-cyclodextrin with an open cavity. Based on these observations, we investigate the hypothesis that the expulsion of thermodynamically unfavorable water molecules into the bulk plays an important role in controlling the accessibility of the closed macrostate at room temperature. We compare the results of the molecular mechanics analytical generalized Born plus nonpolar solvation approach to those obtained through grid inhomogeneous solvation theory analysis with explicit solvation to elucidate the thermodynamic forces at play. The work illustrates the use of continuum solvent models to tease out solvation effects related to the inhomogeneity and the molecular nature of water and demonstrates the key role of the thermodynamics of enclosed hydration in driving the conformational equilibrium of molecules in solution.
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Affiliation(s)
- Peng He
- Center for Biophysics & Computational Biology/ICMS, Department of Chemistry , Temple University , Philadelphia , Pennsylvania 19122 , United States
| | - Sheila Sarkar
- Department of Science , Borough of Manhattan Community College, The City University of New York , New York , New York 10007 , United States
| | - Emilio Gallicchio
- Department of Chemistry , Brooklyn College, The City University of New York , Brooklyn , New York 11210 , United States.,Ph.D. Programs in Chemistry & Biochemistry , The Graduate Center of the City University of New York , 365 Fifth Avenue , New York , New York 10016 , United States
| | - Tom Kurtzman
- Department of Chemistry , Lehman College, The City University of New York , Bronx , New York 10468 , United States.,Ph.D. Programs in Chemistry & Biochemistry , The Graduate Center of the City University of New York , 365 Fifth Avenue , New York , New York 10016 , United States
| | - Lauren Wickstrom
- Department of Science , Borough of Manhattan Community College, The City University of New York , New York , New York 10007 , United States
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6
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Pal RK, Gadhiya S, Ramsey S, Cordone P, Wickstrom L, Harding WW, Kurtzman T, Gallicchio E. Inclusion of enclosed hydration effects in the binding free energy estimation of dopamine D3 receptor complexes. PLoS One 2019; 14:e0222902. [PMID: 31568493 PMCID: PMC6768453 DOI: 10.1371/journal.pone.0222902] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 08/30/2019] [Indexed: 01/04/2023] Open
Abstract
Confined hydration and conformational flexibility are some of the challenges encountered for the rational design of selective antagonists of G-protein coupled receptors. We present a set of C3-substituted (-)-stepholidine derivatives as potent binders of the dopamine D3 receptor. The compounds are characterized biochemically, as well as by computer modeling using a novel molecular dynamics-based alchemical binding free energy approach which incorporates the effect of the displacement of enclosed water molecules from the binding site. The free energy of displacement of specific hydration sites is obtained using the Hydration Site Analysis method with explicit solvation. This work underscores the critical role of confined hydration and conformational reorganization in the molecular recognition mechanism of dopamine receptors and illustrates the potential of binding free energy models to represent these key phenomena.
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Affiliation(s)
- Rajat Kumar Pal
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, NY 11210, United States of America
- PhD Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
| | - Satishkumar Gadhiya
- PhD Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- Department of Chemistry, Hunter College, 695 Park Avenue, NY 10065, United States of America
| | - Steven Ramsey
- PhD Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- Department of Chemistry, Lehman College, 250 Bedford Park Blvd. West, Bronx, NY 10468, United States of America
| | - Pierpaolo Cordone
- PhD Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- Department of Chemistry, Hunter College, 695 Park Avenue, NY 10065, United States of America
| | - Lauren Wickstrom
- Department of Science, Borough of Manhattan Community College, 199 Chambers Street, New York, NY 10007, United States of America
| | - Wayne W. Harding
- PhD Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- PhD Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- Department of Chemistry, Hunter College, 695 Park Avenue, NY 10065, United States of America
| | - Tom Kurtzman
- PhD Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- PhD Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- Department of Chemistry, Lehman College, 250 Bedford Park Blvd. West, Bronx, NY 10468, United States of America
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, NY 11210, United States of America
- PhD Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- PhD Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States of America
- * E-mail:
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7
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Deng N, Xia J, Wickstrom L, Lin C, Wang K, He P, Yin Y, Yang D. Ligand Selectivity in the Recognition of Protoberberine Alkaloids by Hybrid-2 Human Telomeric G-Quadruplex: Binding Free Energy Calculation, Fluorescence Binding, and NMR Experiments. Molecules 2019; 24:molecules24081574. [PMID: 31010072 PMCID: PMC6515380 DOI: 10.3390/molecules24081574] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 04/15/2019] [Accepted: 04/19/2019] [Indexed: 11/23/2022] Open
Abstract
The human telomeric G-quadruplex (G4) is an attractive target for developing anticancer drugs. Natural products protoberberine alkaloids are known to bind human telomeric G4 and inhibit telomerase. Among several structurally similar protoberberine alkaloids, epiberberine (EPI) shows the greatest specificity in recognizing the human telomeric G4 over duplex DNA and other G4s. Recently, NMR study revealed that EPI recognizes specifically the hybrid-2 form human telomeric G4 by inducing large rearrangements in the 5′-flanking segment and loop regions to form a highly extensive four-layered binding pocket. Using the NMR structure of the EPI-human telomeric G4 complex, here we perform molecular dynamics free energy calculations to elucidate the ligand selectivity in the recognition of protoberberines by the human telomeric G4. The MM-PB(GB)SA (molecular mechanics-Poisson Boltzmann/Generalized Born) Surface Area) binding free energies calculated using the Amber force fields bsc0 and OL15 correlate well with the NMR titration and binding affinity measurements, with both calculations correctly identifying the EPI as the strongest binder to the hybrid-2 telomeric G4 wtTel26. The results demonstrated that accounting for the conformational flexibility of the DNA-ligand complexes is crucially important for explaining the ligand selectivity of the human telomeric G4. While the MD-simulated (molecular dynamics) structures of the G-quadruplex-alkaloid complexes help rationalize why the EPI-G4 interactions are optimal compared with the other protoberberines, structural deviations from the NMR structure near the binding site are observed in the MD simulations. We have also performed binding free energy calculation using the more rigorous double decoupling method (DDM); however, the results correlate less well with the experimental trend, likely due to the difficulty of adequately sampling the very large conformational reorganization in the G4 induced by the protoberberine binding.
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Affiliation(s)
- Nanjie Deng
- Department of Chemistry and Physical Sciences, Pace University, New York, NY 10038, USA.
| | - Junchao Xia
- Department of Mathematics and Department of Research Computing, Princeton University, Princeton, NJ 08544, USA.
| | - Lauren Wickstrom
- Department of Science, Borough of Manhattan Community College, the City University of New York, New York, NY 10007, USA.
| | - Clement Lin
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA.
| | - Kaibo Wang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA.
| | - Peng He
- James Frank Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA.
| | - Yunting Yin
- Department of Chemistry and Physical Sciences, Pace University, New York, NY 10038, USA.
| | - Danzhou Yang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA.
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8
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Gadhiya S, Cordone P, Pal RK, Gallicchio E, Wickstrom L, Kurtzman T, Ramsey S, Harding WW. New Dopamine D3-Selective Receptor Ligands Containing a 6-Methoxy-1,2,3,4-tetrahydroisoquinolin-7-ol Motif. ACS Med Chem Lett 2018; 9:990-995. [PMID: 30344905 DOI: 10.1021/acsmedchemlett.8b00229] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 09/10/2018] [Indexed: 11/29/2022] Open
Abstract
A series of analogues featuring a 6-methoxy-1,2,3,4-tetrahydroisoquinolin-7-ol unit as the arylamine "head" group of a classical D3 antagonist core structure were synthesized and evaluated for affinity at dopamine D1, D2, and D3 receptors (D1R, D2R, D3R). The compounds generally displayed strong affinity for D3R with very good D3R selectivity. Docking studies at D2R and D3R crystal structures revealed that the molecules are oriented such that their arylamine units are positioned in the orthosteric binding pocket of D3R, with the arylamide "tail" units residing in the secondary binding pocket. Hydrogen bonding between Ser 182 and Tyr 365 at D3R stabilize extracellular loop 2 (ECL2), which in turn contributes to ligand binding by interacting with the "tail" units of the ligands in the secondary binding pocket. Similar interactions between ECL2 and the "tail" units were absent at D2R due to different positioning of the D2R loop region. The presence of multiple H-bonds with the phenol moiety of the headgroup of 7 and Ser192 accounts for its stronger D3R affinity as compared to the 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline-containing analogue 8.
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Affiliation(s)
- Satishkumar Gadhiya
- Department of Chemistry, Hunter College, City University of New York, 695 Park Avenue, New York, New York 10065, United States
- Ph.D. Program in Chemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
| | - Pierpaolo Cordone
- Department of Chemistry, Hunter College, City University of New York, 695 Park Avenue, New York, New York 10065, United States
- Ph.D. Program in Biochemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
| | - Rajat K. Pal
- Ph.D. Program in Biochemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11210, United States
| | - Emilio Gallicchio
- Ph.D. Program in Chemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Ph.D. Program in Biochemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11210, United States
| | - Lauren Wickstrom
- Department of Science, Borough of Manhattan Community College, 199 Chambers Street, New York, New York 10007, United States
| | - Tom Kurtzman
- Ph.D. Program in Chemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Ph.D. Program in Biochemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Department of Chemistry, Lehman College, The City University of New York, Bronx, New York 10468, United States
| | - Steven Ramsey
- Ph.D. Program in Biochemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Department of Chemistry, Lehman College, The City University of New York, Bronx, New York 10468, United States
| | - Wayne W. Harding
- Department of Chemistry, Hunter College, City University of New York, 695 Park Avenue, New York, New York 10065, United States
- Ph.D. Program in Chemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Ph.D. Program in Biochemistry, CUNY Graduate Center, 365 Fifth Avenue, New York, New York 10016, United States
- Department of Chemistry, Lehman College, The City University of New York, Bronx, New York 10468, United States
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9
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Martinez-del Campo LJ, Greer N, Trent A, Stoner LJ, Wickstrom L, Loch D, Kobluk CN. The Use of High-Speed Videography to Generate Angle-Time and Angle-Angle Diagrams for the Study of Equine Locomotion. Vet Comp Orthop Traumatol 2018. [DOI: 10.1055/s-0038-1633266] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Summary
Introduction
High-speed videography was used to generate angle-time and angle-angle diagrams to provide the basis for a better subjective and objective understanding of the locomotor function of the horse. Intra- and interlimb coordination patterns were analyzed in a group of ten clinically sound racing Thoroughbreds. For lateral video recording, reflective markers were glued over the axis of rotation of the fore- and hindlimb joints of the ten horses. All horses were filmed simultaneously from both sides (right and left). Means and standard deviations were calculated for the minimum, the maximum and the range of motion values for the angle excursions of each joint. Angle-time and angle-angle diagrams were highly repeatable over the eight to nine strides videotaped for each horse and showed a very characteristic shape with minor variations between individual horses. When comparing right versus left sides, horses exhibited varying levels of significant asymmetry.
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10
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Deng N, Wickstrom L, Cieplak P, Lin C, Yang D. Resolving the Ligand-Binding Specificity in c-MYC G-Quadruplex DNA: Absolute Binding Free Energy Calculations and SPR Experiment. J Phys Chem B 2017; 121:10484-10497. [PMID: 29086571 DOI: 10.1021/acs.jpcb.7b09406] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We report the absolute binding free energy calculation and surface plasmon resonance (SPR) experiment for ligand binding with the c-MYC G-quadruplex DNA. The unimolecular parallel DNA G-quadruplex formed in nuclease hypersensitivity element III1 of the c-MYC gene promoter regulates the c-MYC transcription and is recognized as an emerging drug target for cancer therapy. Quindoline derivatives have been shown to stabilize the G-quadruplex and inhibit the c-MYC expression in cancer cells. NMR revealed two binding sites located at the 5' and 3' termini of the G-quadruplex. Questions about which site is more favored and the basis for the ligand-induced binding site formation remain unresolved. Here, we employ two absolute binding free energy methods, the double decoupling and the potential of mean force methods, to dissect the ligand-binding specificity in the c-MYC G-quadruplex. The calculated absolute binding free energies are in general agreement with the SPR result and suggest that quindoline has a slight preference for the 5' site. The flanking residues around the two sites undergo significant reorganization as the ligand unbinds, which provides evidence for ligand-induced binding pocket formation. The results help interpret experimental data and inform rational design of small molecules targeting the c-MYC G-quadruplex.
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Affiliation(s)
- Nanjie Deng
- Department of Chemistry and Physical Sciences, Pace University , 1 Pace Plaza, New York, New York 10038, United States
| | - Lauren Wickstrom
- Department of Science, Borough of Manhattan Community College, the City University of New York , New York, New York 10007, United States
| | - Piotr Cieplak
- Sanford Burnham Prebys Medical Discovery Institute , La Jolla, San Diego, California 92037, United States
| | - Clement Lin
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University , West Lafayette, Indiana 47907, United States
| | - Danzhou Yang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University , West Lafayette, Indiana 47907, United States
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11
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Pal RK, Haider K, Kaur D, Flynn W, Xia J, Levy RM, Taran T, Wickstrom L, Kurtzman T, Gallicchio E. Erratum to: A combined treatment of hydration and dynamical effects for the modeling of host-guest binding thermodynamics: the SAMPL5 blinded challenge. J Comput Aided Mol Des 2016; 31:45. [PMID: 27815770 DOI: 10.1007/s10822-016-9987-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rajat Kumar Pal
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, NY, 11210, USA
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Kamran Haider
- Department of Chemistry, Lehman College, The City University of New York, 250 Bedford Park Blvd. West, Bronx, New York, NY, 10468, USA
| | - Divya Kaur
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - William Flynn
- Center for Biophysics and Computational Biology, Institute of Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA, USA
- Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, 08854, USA
| | - Junchao Xia
- Center for Biophysics and Computational Biology, Institute of Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA, USA
| | - Ronald M Levy
- Center for Biophysics and Computational Biology, Institute of Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA, USA
| | - Tetiana Taran
- Borough of Manhattan Community College, Department of Science, The City University of New York, 199 Chambers Street, New York, NY, 10007, USA
| | - Lauren Wickstrom
- Borough of Manhattan Community College, Department of Science, The City University of New York, 199 Chambers Street, New York, NY, 10007, USA
| | - Tom Kurtzman
- Department of Chemistry, Lehman College, The City University of New York, 250 Bedford Park Blvd. West, Bronx, New York, NY, 10468, USA
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, NY, 11210, USA.
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
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12
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Pal RK, Haider K, Kaur D, Flynn W, Xia J, Levy RM, Taran T, Wickstrom L, Kurtzman T, Gallicchio E. A combined treatment of hydration and dynamical effects for the modeling of host-guest binding thermodynamics: the SAMPL5 blinded challenge. J Comput Aided Mol Des 2016; 31:29-44. [PMID: 27696239 DOI: 10.1007/s10822-016-9956-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 08/25/2016] [Indexed: 01/02/2023]
Abstract
As part of the SAMPL5 blinded experiment, we computed the absolute binding free energies of 22 host-guest complexes employing a novel approach based on the BEDAM single-decoupling alchemical free energy protocol with parallel replica exchange conformational sampling and the AGBNP2 implicit solvation model specifically customized to treat the effect of water displacement as modeled by the Hydration Site Analysis method with explicit solvation. Initial predictions were affected by the lack of treatment of ionic charge screening, which is very significant for these highly charged hosts, and resulted in poor relative ranking of negatively versus positively charged guests. Binding free energies obtained with Debye-Hückel treatment of salt effects were in good agreement with experimental measurements. Water displacement effects contributed favorably and very significantly to the observed binding affinities; without it, the modeling predictions would have grossly underestimated binding. The work validates the implicit/explicit solvation approach employed here and it shows that comprehensive physical models can be effective at predicting binding affinities of molecular complexes requiring accurate treatment of conformational dynamics and hydration.
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Affiliation(s)
- Rajat Kumar Pal
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York, 11210, USA
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Kamran Haider
- Department of Chemistry, Lehman College, The City University of New York, 250 Bedford Park Blvd. West, Bronx, New York, NY, 10468, USA
| | - Divya Kaur
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - William Flynn
- Center for Biophysics and Computational Biology, Institute of Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA, USA
- Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, 08854, USA
| | - Junchao Xia
- Center for Biophysics and Computational Biology, Institute of Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA, USA
| | - Ronald M Levy
- Center for Biophysics and Computational Biology, Institute of Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA, USA
| | - Tetiana Taran
- Borough of Manhattan Community College, Department of Science, The City University of New York, 199 Chambers Street, New York, NY, 10007, USA
| | - Lauren Wickstrom
- Borough of Manhattan Community College, Department of Science, The City University of New York, 199 Chambers Street, New York, NY, 10007, USA
| | - Tom Kurtzman
- Department of Chemistry, Lehman College, The City University of New York, 250 Bedford Park Blvd. West, Bronx, New York, NY, 10468, USA
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York, 11210, USA.
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
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13
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Abstract
The principles underlying water reorganization around simple nonpolar solutes are well understood and provide the framework for the classical hydrophobic effect, whereby water molecules structure themselves around solutes so that they maintain favorable energetic contacts with both the solute and the other water molecules. However, for certain solute surface topographies, water molecules, due to their geometry and size, are unable to simultaneously maintain favorable energetic contacts with both the surface and neighboring water molecules. In this study, we analyze the solvation of ligand-binding sites for six structurally diverse proteins using hydration site analysis and measures of local water structure, in order to identify surfaces at which water molecules are unable to structure themselves in a way that maintains favorable enthalpy relative to bulk water. These surfaces are characterized by a high degree of enclosure, weak solute-water interactions, and surface constraints that induce unfavorable pair interactions between neighboring water molecules. Additionally, we find that the solvation of charged side chains in an active site generally results in favorable enthalpy but can also lead to pair interactions between neighboring water molecules that are significantly unfavorable relative to bulk water. We find that frustrated local structure can occur not only in apolar and weakly polar pockets, where overall enthalpy tends to be unfavorable, but also in charged pockets, where overall water enthalpy tends to be favorable. The characterization of local water structure in these terms may prove useful for evaluating the displacement of water from diverse protein active-site environments.
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Affiliation(s)
- Kamran Haider
- Department of Chemistry, Lehman College, The City University of New York , 250 Bedford Park Boulevard West, Bronx, New York 10468, United States
| | - Lauren Wickstrom
- Borough of Manhattan Community College, Department of Science, The City University of New York , 199 Chambers Street, New York, New York 10007, United States
| | - Steven Ramsey
- Department of Chemistry, Lehman College, The City University of New York , 250 Bedford Park Boulevard West, Bronx, New York 10468, United States.,Ph.D. Program in Biochemistry, The Graduate Center of The City University of New York , 365 Fifth Avenue, New York, New York 10016, United States
| | - Michael K Gilson
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego , 9500 Gilman Drive, La Jolla, California 92093-0736, United States
| | - Tom Kurtzman
- Department of Chemistry, Lehman College, The City University of New York , 250 Bedford Park Boulevard West, Bronx, New York 10468, United States.,Ph.D. Program in Biochemistry, The Graduate Center of The City University of New York , 365 Fifth Avenue, New York, New York 10016, United States.,Ph.D. Program in Chemistry, The Graduate Center of The City University of New York , 365 Fifth Avenue, New York, New York 10016, United States
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14
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Okur A, Wickstrom L, Layten M, Geney R, Song K, Hornak V, Simmerling C. Improved Efficiency of Replica Exchange Simulations through Use of a Hybrid Explicit/Implicit Solvation Model. J Chem Theory Comput 2015; 2:420-33. [PMID: 26626529 DOI: 10.1021/ct050196z] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The use of parallel tempering or replica exchange molecular dynamics (REMD) simulations has facilitated the exploration of free energy landscapes for complex molecular systems, but application to large systems is hampered by the scaling of the number of required replicas with increasing system size. Use of continuum solvent models reduces system size and replica requirements, but these have been shown to provide poor results in many cases, including overstabilization of ion pairs and secondary structure bias. Hybrid explicit/continuum solvent models can overcome some of these problems through an explicit representation of water molecules in the first solvation shells, but these methods typically require restraints on the solvent molecules and show artifacts in water properties due to the solvation interface. We propose an REMD variant in which the simulations are performed with a fully explicit solvent, but the calculation of exchange probability is carried out using a hybrid model, with the solvation shells calculated on the fly during the fully solvated simulation. The resulting reduction in the perceived system size in the REMD exchange calculation provides a dramatic decrease in the computational cost of REMD, while maintaining a very good agreement with results obtained from the standard explicit solvent REMD. We applied several standard and hybrid REMD methods with different solvent models to alanine polymers of 1, 3, and 10 residues, obtaining ensembles that were essentially independent of the initial conformation, even with explicit solvation. Use of only a continuum model without a shell of explicit water provided poor results for Ala3 and Ala10, with a significant bias in favor of the α-helix. Likewise, using only the solvation shells and no continuum model resulted in ensembles that differed significantly from the standard explicit solvent data. Ensembles obtained from hybrid REMD are in very close agreement with explicit solvent data, predominantly populating polyproline II conformations. Inclusion of a second shell of explicit solvent was found to be unnecessary for these peptides.
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Affiliation(s)
- Asim Okur
- Department of Chemistry, Graduate Program in Biochemistry and Structural Biology, Graduate Program in Molecular and Cellular Biology, and Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794, and Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973
| | - Lauren Wickstrom
- Department of Chemistry, Graduate Program in Biochemistry and Structural Biology, Graduate Program in Molecular and Cellular Biology, and Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794, and Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973
| | - Melinda Layten
- Department of Chemistry, Graduate Program in Biochemistry and Structural Biology, Graduate Program in Molecular and Cellular Biology, and Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794, and Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973
| | - Raphäel Geney
- Department of Chemistry, Graduate Program in Biochemistry and Structural Biology, Graduate Program in Molecular and Cellular Biology, and Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794, and Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973
| | - Kun Song
- Department of Chemistry, Graduate Program in Biochemistry and Structural Biology, Graduate Program in Molecular and Cellular Biology, and Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794, and Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973
| | - Viktor Hornak
- Department of Chemistry, Graduate Program in Biochemistry and Structural Biology, Graduate Program in Molecular and Cellular Biology, and Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794, and Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973
| | - Carlos Simmerling
- Department of Chemistry, Graduate Program in Biochemistry and Structural Biology, Graduate Program in Molecular and Cellular Biology, and Center for Structural Biology, Stony Brook University, Stony Brook, New York 11794, and Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973
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15
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Wickstrom L, Deng N, He P, Mentes A, Nguyen C, Gilson MK, Kurtzman T, Gallicchio E, Levy RM. Parameterization of an effective potential for protein-ligand binding from host-guest affinity data. J Mol Recognit 2015; 29:10-21. [PMID: 26256816 DOI: 10.1002/jmr.2489] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 06/06/2015] [Accepted: 06/07/2015] [Indexed: 12/13/2022]
Abstract
Force field accuracy is still one of the "stalemates" in biomolecular modeling. Model systems with high quality experimental data are valuable instruments for the validation and improvement of effective potentials. With respect to protein-ligand binding, organic host-guest complexes have long served as models for both experimental and computational studies because of the abundance of binding affinity data available for such systems. Binding affinity data collected for cyclodextrin (CD) inclusion complexes, a popular model for molecular recognition, is potentially a more reliable resource for tuning energy parameters than hydration free energy measurements. Convergence of binding free energy calculations on CD host-guest systems can also be obtained rapidly, thus offering the opportunity to assess the robustness of these parameters. In this work, we demonstrate how implicit solvent parameters can be developed using binding affinity experimental data and the binding energy distribution analysis method (BEDAM) and validated using the Grid Inhomogeneous Solvation Theory analysis. These new solvation parameters were used to study protein-ligand binding in two drug targets against the HIV-1 virus and improved the agreement between the calculated and the experimental binding affinities. This work illustrates how benchmark sets of high quality experimental binding affinity data and physics-based binding free energy models can be used to evaluate and optimize force fields for protein-ligand systems. Copyright © 2015 John Wiley & Sons, Ltd.
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Affiliation(s)
- Lauren Wickstrom
- Borough of Manhattan Community College, Department of Science, The City University of New York, New York, NY, 10007, USA
| | - Nanjie Deng
- Center for Biophysics and Computational Biology/ICMS, Department of Chemistry, Temple University, Philadelphia, PA, 19122, USA
| | - Peng He
- Center for Biophysics and Computational Biology/ICMS, Department of Chemistry, Temple University, Philadelphia, PA, 19122, USA
| | - Ahmet Mentes
- Center for Biophysics and Computational Biology/ICMS, Department of Chemistry, Temple University, Philadelphia, PA, 19122, USA
| | - Crystal Nguyen
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, 92093-0736, USA
| | - Michael K Gilson
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, 92093-0736, USA
| | - Tom Kurtzman
- Department of Chemistry, Lehman College, The City University of New York, Bronx, NY, 10468, USA
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, NY, 11210, USA
| | - Ronald M Levy
- Center for Biophysics and Computational Biology/ICMS, Department of Chemistry, Temple University, Philadelphia, PA, 19122, USA
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16
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Maier JA, Martinez C, Kasavajhala K, Wickstrom L, Hauser KE, Simmerling C. ff14SB: Improving the Accuracy of Protein Side Chain and Backbone Parameters from ff99SB. J Chem Theory Comput 2015; 11:3696-713. [PMID: 26574453 DOI: 10.1021/acs.jctc.5b00255] [Citation(s) in RCA: 6187] [Impact Index Per Article: 687.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular mechanics is powerful for its speed in atomistic simulations, but an accurate force field is required. The Amber ff99SB force field improved protein secondary structure balance and dynamics from earlier force fields like ff99, but weaknesses in side chain rotamer and backbone secondary structure preferences have been identified. Here, we performed a complete refit of all amino acid side chain dihedral parameters, which had been carried over from ff94. The training set of conformations included multidimensional dihedral scans designed to improve transferability of the parameters. Improvement in all amino acids was obtained as compared to ff99SB. Parameters were also generated for alternate protonation states of ionizable side chains. Average errors in relative energies of pairs of conformations were under 1.0 kcal/mol as compared to QM, reduced 35% from ff99SB. We also took the opportunity to make empirical adjustments to the protein backbone dihedral parameters as compared to ff99SB. Multiple small adjustments of φ and ψ parameters were tested against NMR scalar coupling data and secondary structure content for short peptides. The best results were obtained from a physically motivated adjustment to the φ rotational profile that compensates for lack of ff99SB QM training data in the β-ppII transition region. Together, these backbone and side chain modifications (hereafter called ff14SB) not only better reproduced their benchmarks, but also improved secondary structure content in small peptides and reproduction of NMR χ1 scalar coupling measurements for proteins in solution. We also discuss the Amber ff12SB parameter set, a preliminary version of ff14SB that includes most of its improvements.
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Affiliation(s)
- James A Maier
- Graduate Program in Biochemistry and Structural Biology, ‡Department of Chemistry, and §Laufer Center for Physical and Quantitative Biology, Stony Brook University , Stony Brook, New York 11794, United States
| | - Carmenza Martinez
- Graduate Program in Biochemistry and Structural Biology, ‡Department of Chemistry, and §Laufer Center for Physical and Quantitative Biology, Stony Brook University , Stony Brook, New York 11794, United States
| | - Koushik Kasavajhala
- Graduate Program in Biochemistry and Structural Biology, ‡Department of Chemistry, and §Laufer Center for Physical and Quantitative Biology, Stony Brook University , Stony Brook, New York 11794, United States
| | - Lauren Wickstrom
- Graduate Program in Biochemistry and Structural Biology, ‡Department of Chemistry, and §Laufer Center for Physical and Quantitative Biology, Stony Brook University , Stony Brook, New York 11794, United States
| | - Kevin E Hauser
- Graduate Program in Biochemistry and Structural Biology, ‡Department of Chemistry, and §Laufer Center for Physical and Quantitative Biology, Stony Brook University , Stony Brook, New York 11794, United States
| | - Carlos Simmerling
- Graduate Program in Biochemistry and Structural Biology, ‡Department of Chemistry, and §Laufer Center for Physical and Quantitative Biology, Stony Brook University , Stony Brook, New York 11794, United States
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17
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Deng N, Forli S, He P, Perryman A, Wickstrom L, Vijayan RSK, Tiefenbrunn T, Stout D, Gallicchio E, Olson AJ, Levy RM. Distinguishing binders from false positives by free energy calculations: fragment screening against the flap site of HIV protease. J Phys Chem B 2014; 119:976-88. [PMID: 25189630 PMCID: PMC4306491 DOI: 10.1021/jp506376z] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
![]()
Molecular docking is a powerful tool
used in drug discovery and
structural biology for predicting the structures of ligand–receptor
complexes. However, the accuracy of docking calculations can be limited
by factors such as the neglect of protein reorganization in the scoring
function; as a result, ligand screening can produce a high rate of
false positive hits. Although absolute binding free energy methods
still have difficulty in accurately rank-ordering binders, we believe
that they can be fruitfully employed to distinguish binders from nonbinders
and reduce the false positive rate. Here we study a set of ligands
that dock favorably to a newly discovered, potentially allosteric
site on the flap of HIV-1 protease. Fragment binding to this site
stabilizes a closed form of protease, which could be exploited for
the design of allosteric inhibitors. Twenty-three top-ranked protein–ligand
complexes from AutoDock were subject to the free energy screening
using two methods, the recently developed binding energy analysis
method (BEDAM) and the standard double decoupling method (DDM). Free
energy calculations correctly identified most of the false positives
(≥83%) and recovered all the confirmed binders. The results
show a gap averaging ≥3.7 kcal/mol, separating the binders
and the false positives. We present a formula that decomposes the
binding free energy into contributions from the receptor conformational
macrostates, which provides insights into the roles of different binding
modes. Our binding free energy component analysis further suggests
that improving the treatment for the desolvation penalty associated
with the unfulfilled polar groups could reduce the rate of false positive
hits in docking. The current study demonstrates that the combination
of docking with free energy methods can be very useful for more accurate
ligand screening against valuable drug targets.
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Affiliation(s)
- Nanjie Deng
- Center for Biophysics & Computational Biology/ICMS, ‡Department of Chemistry, Temple University , Philadelphia, Pennsylvania19122, United States
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18
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Wickstrom L, He P, Gallicchio E, Levy RM. Large scale affinity calculations of cyclodextrin host-guest complexes: Understanding the role of reorganization in the molecular recognition process. J Chem Theory Comput 2013; 9:3136-3150. [PMID: 25147485 DOI: 10.1021/ct400003r] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Host-guest inclusion complexes are useful models for understanding the structural and energetic aspects of molecular recognition. Due to their small size relative to much larger protein-ligand complexes, converged results can be obtained rapidly for these systems thus offering the opportunity to more reliably study fundamental aspects of the thermodynamics of binding. In this work, we have performed a large scale binding affinity survey of 57 β-cyclodextrin (CD) host guest systems using the binding energy distribution analysis method (BEDAM) with implicit solvation (OPLS-AA/AGBNP2). Converged estimates of the standard binding free energies are obtained for these systems by employing techniques such as parallel Hamitionian replica exchange molecular dynamics, conformational reservoirs and multistate free energy estimators. Good agreement with experimental measurements is obtained in terms of both numerical accuracy and affinity rankings. Overall, average effective binding energies reproduce affinity rank ordering better than the calculated binding affinities, even though calculated binding free energies, which account for effects such as conformational strain and entropy loss upon binding, provide lower root mean square errors when compared to measurements. Interestingly, we find that binding free energies are superior rank order predictors for a large subset containing the most flexible guests. The results indicate that, while challenging, accurate modeling of reorganization effects can lead to ligand design models of superior predictive power for rank ordering relative to models based only on ligand-receptor interaction energies.
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Affiliation(s)
- Lauren Wickstrom
- BioMaPS Institute for Quantitative Biology and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854 ; Department of Chemistry, Lehman College, The City University of New York, Bronx, NY 10468
| | - Peng He
- BioMaPS Institute for Quantitative Biology and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854
| | - Emilio Gallicchio
- BioMaPS Institute for Quantitative Biology and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854
| | - Ronald M Levy
- BioMaPS Institute for Quantitative Biology and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854
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19
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Wickstrom L, Gallicchio E, Levy RM. The linear interaction energy method for the prediction of protein stability changes upon mutation. Proteins 2011; 80:111-25. [PMID: 22038697 DOI: 10.1002/prot.23168] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 07/28/2011] [Accepted: 08/06/2011] [Indexed: 12/25/2022]
Abstract
The coupling of protein energetics and sequence changes is a critical aspect of computational protein design, as well as for the understanding of protein evolution, human disease, and drug resistance. To study the molecular basis for this coupling, computational tools must be sufficiently accurate and computationally inexpensive enough to handle large amounts of sequence data. We have developed a computational approach based on the linear interaction energy (LIE) approximation to predict the changes in the free-energy of the native state induced by a single mutation. This approach was applied to a set of 822 mutations in 10 proteins which resulted in an average unsigned error of 0.82 kcal/mol and a correlation coefficient of 0.72 between the calculated and experimental ΔΔG values. The method is able to accurately identify destabilizing hot spot mutations; however, it has difficulty in distinguishing between stabilizing and destabilizing mutations because of the distribution of stability changes for the set of mutations used to parameterize the model. In addition, the model also performs quite well in initial tests on a small set of double mutations. On the basis of these promising results, we can begin to examine the relationship between protein stability and fitness, correlated mutations, and drug resistance.
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Affiliation(s)
- Lauren Wickstrom
- Department of Chemistry and Chemical Biology, BioMaPS Institute for Quantitative Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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20
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Shang Y, Nguyen H, Wickstrom L, Okur A, Simmerling C. Improving the description of salt bridge strength and geometry in a Generalized Born model. J Mol Graph Model 2010; 29:676-84. [PMID: 21168352 DOI: 10.1016/j.jmgm.2010.11.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Accepted: 11/22/2010] [Indexed: 10/18/2022]
Abstract
The Generalized Born (GB) solvent model is widely used in molecular dynamics simulations because it can be less computationally expensive and it samples conformational changes more efficiently than explicit solvent simulations. Meanwhile, great efforts have been made in the past to improve its precision and accuracy. Previous studies have shown that reducing intrinsic GB radii of some hydrogen atoms would improve AMBER GB-HCT solvent model's accuracy on salt bridges. Here we present our finding that similar correction also shows dramatic improvement for the AMBER GB-OBC solvent model. Potential of mean force and cluster analysis for small peptide replica exchange molecular dynamics simulations suggested that new radii GB simulation with ff99SB/GB-OBC corrected salt bridge strength and achieved significantly higher geometry similarity with TIP3P simulation. Improved performance in 60 ns HIV-1 protease GB simulation further validated this approach for large systems.
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Affiliation(s)
- Yi Shang
- Graduate Program in Molecular and Cellular Biology, Stony Brook University, Stony Brook, NY 11794, USA.
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Wickstrom L, Okur A, Simmerling C. Evaluating the performance of the ff99SB force field based on NMR scalar coupling data. Biophys J 2009; 97:853-6. [PMID: 19651043 DOI: 10.1016/j.bpj.2009.04.063] [Citation(s) in RCA: 184] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 03/30/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022] Open
Abstract
Force-field validation is essential for the identification of weaknesses in current models and the development of more accurate models of biomolecules. NMR coupling and relaxation methods have been used to effectively diagnose the strengths and weaknesses of many existing force fields. Studies using the ff99SB force field have shown excellent agreement between experimental and calculated order parameters and residual dipolar calculations. However, recent studies have suggested that ff99SB demonstrates poor agreement with J-coupling constants for short polyalanines. We performed extensive replica-exchange molecular-dynamics simulations on Ala(3) and Ala(5) in TIP3P and TIP4P-Ew solvent models. Our results suggest that the performance of ff99SB is among the best of currently available models. In addition, scalar coupling constants derived from simulations in the TIP4P-Ew model show a slight improvement over those obtained using the TIP3P model. Despite the overall excellent agreement, the data suggest areas for possible improvement.
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Affiliation(s)
- Lauren Wickstrom
- Biochemistry and Structural Biology Program, State University of New York, Stony Brook, New York, USA
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Okur A, Wickstrom L, Simmerling C. Evaluation of Salt Bridge Structure and Energetics in Peptides Using Explicit, Implicit, and Hybrid Solvation Models. J Chem Theory Comput 2008; 4:488-98. [DOI: 10.1021/ct7002308] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Asim Okur
- Department of Chemistry and Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794
| | - Lauren Wickstrom
- Department of Chemistry and Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794
| | - Carlos Simmerling
- Department of Chemistry and Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794
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Wickstrom L, Bi Y, Hornak V, Raleigh DP, Simmerling CL. Reconciling the solution and X-ray structures of the villin headpiece helical subdomain: molecular dynamics simulations and double mutant cycles reveal a stabilizing cation-pi interaction. Biochemistry 2007; 46:3624-34. [PMID: 17338549 PMCID: PMC4822197 DOI: 10.1021/bi061785+] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 36-residue helical subdomain of the villin headpiece, HP36, is one of the smallest cooperatively folded proteins, folding on the microsecond time scale. The domain is an extraordinarily popular model system for both experimental and computational studies of protein folding. The structure of HP36 has been determined using X-ray crystallography and NMR spectroscopy, with the resulting structures exhibiting differences in helix packing, van der Waals contacts, and hydrogen bonding. It is important to determine the solution structure of HP36 with as much accuracy as possible since this structure is widely used as a reference for simulations and experiments. We complement the existing data by using all-atom molecular dynamics simulations with explicit solvent to evaluate which of the experimental models is the better representation of HP36 in solution. After simulation for 50 ns initiated with the NMR structure, we observed that the protein spontaneously adopts structures with a backbone conformation, core packing, and C-capping motif on the third helix that are more consistent with the crystal structure. We also examined hydrogen bonding and side chain packing interactions between D44 and R55 and between F47 and R55, respectively, which were observed in the crystal structure but not in the NMR-based solution structure. Simulations showed large fluctuations in the distance between D44 and R55, while the distance between F47 and R55 remained stable, suggesting the formation of a cation-pi interaction between those residues. Experimental double mutant cycles confirmed that the F47-R55 pair has a larger energetic coupling than the D44-R55 interaction. Overall, these combined experimental and computational studies show that the X-ray crystal structure is the better reference structure for HP36 in solution at neutral pH. Our analysis also shows how detailed molecular dynamics simulations combined with experimental validation can help bridge the gap between NMR and crystallographic methods.
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Affiliation(s)
- Lauren Wickstrom
- Biochemistry and Structural Biology Program, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
| | - Yuan Bi
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
| | | | - Daniel P. Raleigh
- Biochemistry and Structural Biology Program, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
- Graduate Program in Biophysics, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
- To whom correspondence should be addressed: , (631-632-1336 (phone), 631-632-1555 (fax)) and , (631)-632-9547 (phone), (631)-632-7960(fax)
| | - Carlos L. Simmerling
- Biochemistry and Structural Biology Program, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
- Center for Structural Biology, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
- To whom correspondence should be addressed: , (631-632-1336 (phone), 631-632-1555 (fax)) and , (631)-632-9547 (phone), (631)-632-7960(fax)
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Roe DR, Okur A, Wickstrom L, Hornak V, Simmerling C. Secondary structure bias in generalized Born solvent models: comparison of conformational ensembles and free energy of solvent polarization from explicit and implicit solvation. J Phys Chem B 2007; 111:1846-57. [PMID: 17256983 PMCID: PMC4810457 DOI: 10.1021/jp066831u] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of the use of three generalized Born (GB) implicit solvent models on the thermodynamics of a simple polyalanine peptide are studied via comparing several hundred nanoseconds of well-converged replica exchange molecular dynamics (REMD) simulations using explicit TIP3P solvent to REMD simulations with the GB solvent models. It is found that when compared to REMD simulations using TIP3P the GB REMD simulations contain significant differences in secondary structure populations, most notably an overabundance of alpha-helical secondary structure. This discrepancy is explored via comparison of the differences in the electrostatic component of the free energy of solvation (DeltaDeltaG(pol)) between TIP3P (via thermodynamic Integration calculations), the GB models, and an implicit solvent model based on the Poisson equation (PE). The electrostatic components of the solvation free energies are calculated using each solvent model for four representative conformations of Ala10. Since the PE model is found to have the best performance with respect to reproducing TIP3P DeltaDeltaG(pol) values, effective Born radii from the GB models are compared to effective Born radii calculated with PE (so-called perfect radii), and significant and numerous deviations in GB radii from perfect radii are found in all GB models. The effect of these deviations on the solvation free energy is discussed, and it is shown that even when perfect radii are used the agreement of GB with TIP3P DeltaDeltaG(pol) values does not improve. This suggests a limit to the optimization of the effective Born radius calculation and that future efforts to improve the accuracy of GB models must extend beyond such optimizations.
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Affiliation(s)
- Daniel R. Roe
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794-3400
| | - Asim Okur
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794-3400
| | - Lauren Wickstrom
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, NY, 11794-3400
| | - Viktor Hornak
- Center for Structural Biology, Stony Brook University, Stony Brook, NY, 11794-3400
| | - Carlos Simmerling
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794-3400
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, NY, 11794-3400
- Center for Structural Biology, Stony Brook University, Stony Brook, NY, 11794-3400
- Computational Science Center, Brookhaven National Laboratory, Upton NY 11973
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Wickstrom L, Okur A, Song K, Hornak V, Raleigh DP, Simmerling CL. The unfolded state of the villin headpiece helical subdomain: computational studies of the role of locally stabilized structure. J Mol Biol 2006; 360:1094-107. [PMID: 16797585 PMCID: PMC4805113 DOI: 10.1016/j.jmb.2006.04.070] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Revised: 04/27/2006] [Accepted: 04/28/2006] [Indexed: 11/19/2022]
Abstract
The 36 residue villin headpiece helical subdomain (HP36) is one of the fastest cooperatively folding proteins, folding on the microsecond timescale. HP36's simple three helix topology, fast folding and small size have made it an attractive model system for computational and experimental studies of protein folding. Recent experimental studies have explored the denatured state of HP36 using fragment analysis coupled with relatively low-resolution spectroscopic techniques. These studies have shown that there is apparently only a small tendency to form locally stabilized secondary structure. Here, we complement the experimental studies by using replica exchange molecular dynamics with explicit solvent to investigate the structural features of these peptide models of unfolded HP36. To ensure convergence, two sets of simulations for each fragment were performed with different initial structures, and simulations were continued until these generated very similar final ensembles. These simulations reveal low populations of native-like structure and early folding events that cannot be resolved by experiment. For each fragment, calculated J-coupling constants and helical propensities are in good agreement with experimental trends. HP-1, corresponding to residues 41 to 53 and including the first alpha-helix, contains the highest helical population. HP-3, corresponding to residues 62 through 75 and including the third alpha-helix, contains a small population of helical turn residing at the N terminus while HP-2, corresponding to residues 52 through 61 and including the second alpha-helix, formed little to no structure in isolation. Overall, HP-1 was the only fragment to adopt a native-like conformation, but the low population suggests that formation of significant structure only occurs after formation of specific tertiary interactions.
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Affiliation(s)
- Lauren Wickstrom
- Biochemistry and Structural Biology Program, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - Asim Okur
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
| | - Kun Song
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
| | - Viktor Hornak
- Center for Structural Biology, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
| | - Daniel P. Raleigh
- Biochemistry and Structural Biology Program, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
- Graduate Program in Biophysics, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - Carlos L. Simmerling
- Biochemistry and Structural Biology Program, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
- Center for Structural Biology, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
- Computational Science Center, Brookhaven National Laboratory, Upton NY 11973, USA
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Abstract
A series of 414 chronic pain patients referred to Are Hospital, Are, Sweden, for evaluation and rehabilitation were administered a structured diagnostic interview to detect alcohol and drug misuse and dependence according to DSM-III-R criteria. A total of 97 (23.4%) met criteria for active alcohol, analgesic, or sedative misuse or dependency; an additional 39 (9.4%) met criteria for a remission diagnosis. Current dependency was most common for analgesics (12.6%) followed by alcohol (9.7%) and sedatives (7.0%).
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Affiliation(s)
- N G Hoffmann
- CATOR/New Standards, Inc., St. Paul, Minnesota, USA
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