Graphical Processing Unit accelerated Poisson equation solver and its application for calculation of single ion potential in ion-channels
Poisson and Poisson-Boltzmann equations (PE and PBE) are widely used in molecular modeling to estimate the electrostatic contribution to the free energy of a system. In such applications, PE often needs to be solved multiple times for a large number of system configurations. This can rapidly become a highly demanding computational task. To accelerate such calculations we implemented a graphical processing unit (GPU) PE solver described in this work. The GPU solver performance is compared to that of our central processing unit (CPU) implementation of the solver. During the performance analysis the following three characteristics were studied: (1) precision associated with the modeled system discretization on the grid, (2) numeric precision associated with the floating point representation of real numbers (this is done via comparison of calculations with single precision (SP) and double precision (DP)), and (3) execution time. Two types of example calculations were carried out to evaluate the solver performance: (1) solvation energy of a single ion and a small protein (lysozyme), and (2) a single ion potential in a large ion-channel (α-hemolysin). In addition, influence of various boundary condition (BC) choices was analyzed, to determine the most appropriate BC for the systems that include a membrane, typically represented by a slab with the dielectric constant of low value. The implemented GPU PE solver is overall about 7 times faster than the CPU-based version (including all four cores). Therefore, a single computer equipped with multiple GPUs can offer a computational power comparable to that of a small cluster. Our calculations showed that DP versions of CPU and GPU solvers provide nearly identical results. SP versions of the solvers have very similar behavior: in the grid scale range of 1-4 grids/Å the difference between SP and DP versions is less than the difference stemming from the system discretization. We found that for the membrane protein, the use of a focusing technique with periodic boundary conditions in rough grid provides significantly better results than using a focusing technique with the electric potential set to zero at the boundaries.
-  J. Antosiewicz, J. A. McCammon, and M. K. Gilson, “Prediction of pH-dependent properties of proteins.,” Journal ofMolecular Biology, vol. 238, no. 3, pp. 415–436, 1994.
-  D. Bashford and M. Karplus, “pKa’s of ionizable groups in proteins: atomic detail from a continuum electrostaticmodel.,” Biochemistry, vol. 29, no. 44, pp. 10219–10225, 1990.
-  S. Bhakdi and J. Tranum-Jensen, “Alpha-toxin of Staphylococcus aureus.,” Microbiological reviews, vol. 55, no. 4,pp. 733–751, 1991.
-  P. M. De Biase, C. J. F. Solano, S. Markosyan, L. Czapla, and S. Y. Noskov, “BROMOC-D: BrownianDynamics/Monte-Carlo Program Suite to Study Ion and DNA Permeation in Nanopores.,” Journal of ChemicalTheory and Computation, vol. 8, no. 7, pp. 2540–2551, 2012.
-  N. Carrascal and D. F. Green, “Energetic decomposition with the generalized-born and Poisson-Boltzmann solventmodels: lessons from association of G-protein components.,” The Journal of Physical Chemistry B, vol. 114, no. 15,pp. 5096–5116, 2010.[WoS]
-  I.-L. Chern, J.-G. Liu, and W.-C. Wang, “Accurate evaluation of electrostatics for macromolecules in solution,” Methodsand Applications of Analysis, vol. 10, no. 2, pp. 309–328, 2003.
-  R. D. Coalson and M. G. Kurnikova, “Poisson-Nernst-Planck theory approach to the calculation of current throughbiological ion channels.,” IEEE Transactions on NanoBioscience, vol. 4, no. 1, pp. 81–93, 2005.
-  M. L. Connolly, “Molecular Surfaces 5. Solvent Accessible Surfaces,” Network Science Corporation. [Online]. Available:http://www.netsci.org/Science/Compchem/feature14e.html.
-  B. Eisenberg, “From Structure to Function in Open Ionic Channels,” The Journal of membrane biology, vol. 171, no.1, pp. 1–24, 2010.
-  M. K. Gilson and B. H. Honig, “Energetics of charge-charge interactions in proteins.,” Proteins, vol. 3, no. 1, pp.32–52, Jan. 1988.[WoS]
-  D. F. Green and B. Tidor, “Evaluation of electrostatic interactions.,” Current protocols in bioinformatics editoralboard Andreas D Baxevanis et al, vol. Chapter 8, p. Unit 8.3, 2003.
-  J. G. Kirkwood, “Theory of solutions of molecules containing widely separated charges with special application tozwitterions,” Journal of Chemical Physics, vol. 2, no. 7, pp. 351–361, 1934.[Crossref]
-  I. Klapper, R. Hagstrom, R. Fine, K. Sharp, and B. Honig, “Focusing of electric fields in the active site of Cu-Znsuperoxide dismutase: effects of ionic strength and amino-acid modification.,” Proteins, vol. 1, no. 1, pp. 47–59,1986.
-  V. Krishnamurthy and S.-H. C. S.-H. Chung, “Brownian dynamics simulation for modeling ion permeation acrossbionanotubes.,” IEEE Transactions on NanoBioscience, vol. 4, no. 1, pp. 102–111, 2005.[Crossref]
-  B. Kuhn and P. A. Kollman, “Binding of a Diverse Set of Ligands to Avidin and Streptavidin: An AccurateQuantitative Prediction of Their Relative Affinities by a Combination of Molecular Mechanics and Continuum SolventModels,” Journal of Medicinal Chemistry, vol. 43, no. 20, pp. 3786–3791, Oct. 2000.
-  B. Lu, M. J. Holst, J. A. McCammon, and Y. C. Zhou, “Poisson-Nernst-Planck equations for simulating biomoleculardiffusion-reaction processes I: Finite element solutions,” Journal of Computational Physics, vol. 229, no. 19, pp.6979–6994, 2010.
-  A. Nicholls and B. Honig, “A rapid finite difference algorithm, utilizing successive over-relaxation to solve thePoisson-Boltzmann equation,” Journal of Computational Chemistry, vol. 12, no. 4, pp. 435–445, 1991.[Crossref]
-  NVIDIA, NVIDIA CUDA C Programming Guide, PG-02829-001_v5.0, no. 350. NVIDIA Corporation, 2012.
-  G. Prévost, L. Mourey, D. A. Colin, and G. Menestrina, “Staphylococcal pore-forming toxins.,” Current Topics inMicrobiology and Immunology, vol. 257, pp. 53–83, 2001.
-  M. Ramanadham, L. C. Sieker, and L. H. Jensen, “Refinement of triclinic lysozyme: II. The method of stereochemicallyrestrained least squares.,” Acta Crystallographica Section B Structural Science, vol. 46, no. 1, pp. 63–69, 1990.
-  W. Rocchia, S. Sridharan, A. Nicholls, E. Alexov, A. Chiabrera, and B. Honig, “Rapid grid-based construction of themolecular surface and the use of induced surface charge to calculate reaction field energies: applications to themolecular systems and geometric objects.,” Journal of Computational Chemistry, vol. 23, no. 1, pp. 128–137, 2002.[Crossref]
-  B. Roux, “Theoretical and computational models of ion channels.,” Current Opinion in Structural Biology, vol. 12,no. 2, pp. 182–189, 2002.[Crossref]
-  N. A. Simakov and M. G. Kurnikova, “Soft wall ion channel in continuum representation with application to modelingion currents in α-hemolysin.,” The journal of physical chemistry. B, vol. 114, no. 46, pp. 15180–90, Dec. 2010.
-  D. Sitkoff, K. A. Sharp, and B. Honig, “Accurate Calculation of Hydration Free Energies Using Macroscopic SolventModels,” Journal of Physical Chemistry, vol. 98, no. 7, pp. 1978–1988, 1994.
-  L. Song, M. R. Hobaugh, C. Shustak, S. Cheley, H. Bayley, and J. E. Gouaux, “Structure of staphylococcal alphahemolysin,a heptameric transmembrane pore.,” Science, vol. 274, no. 5294, pp. 1859–1866, 1996.
-  Y. Song, J. Mao, and M. R. Gunner, “MCCE2: Improving protein pKa calculations with extensive side chain rotamersampling,” Journal of Computational Chemistry, vol. 30, no. 14, pp. 2231–2247, 2009.[WoS]
-  J. Srinivasan, T. E. Cheatham, P. Cieplak, P. A. Kollman, and D. A. Case, “Continuum Solvent Studies of the Stabilityof Continuum Solvent Studies of the Stability of DNA , RNA , and Phosphoramidate-DNA Helices,” Structure, vol.120, no. 37, pp. 9401–9409, 1998.
-  D. J. Vocadlo, G. J. Davies, R. Laine, and S. G. Withers, “Catalysis by hen egg-white lysozyme proceeds via acovalent intermediate,” Nature, vol. 412, no. 6849, pp. 835–838, 2001.
-  Y. C. Zhou, M. Feig, and G. W. Wei, “Highly accurate biomolecular electrostatics in continuum dielectric environments.,”Journal of Computational Chemistry, vol. 29, no. 1, pp. 87–97, 2008.[WoS]