Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 5: Computational Physics

CPP 5.3: Talk

Monday, March 8, 2004, 10:30–10:45, H 39

Statistical Properties of Off-Lattice Heteropolymers — •Michael Bachmann, Wolfhard Janke, and Handan Arkin — Institut für Theoretische Physik, Universität Leipzig, Augustusplatz 10/11, 04109 Leipzig, Germany

We apply a multicanonical algorithm to variants of the AB model [1,2] being an off-lattice model for heteropolymers. Heteropolymers are considered as chains of hydrophobic (A) and hydrophilic (B) monomers only. Into the energy function enter the bending energy and a Lennard-Jones-like potential between nonbonded monomers, where short-range repulsion and long-range attraction compete. Contacts between hydrophobic monomers are favoured, thereby assuming that the global energy minimum state of proteins is characterized by a compact hydrophobic core screened from the solvent by a shell of hydrophilic residues. We calculate thermodynamic quantities for known sequences by means of a modified AB model [2] and identify the temperatures, where conformational pseudo transitions are expected. Since the multicanonical algorithm allows for an accurate sampling of the low-temperature region, we also obtain good estimates for the global energy minimum. Therefore we apply our algorithm to sequences where minimum energies are quoted [3] and compare with lowest-energy states found by minimizing procedures.

[1] F. H. Stillinger, T. Head-Gordon, and C. L. Hirshfeld, Phys. Rev. E 48, 1469 (1993).

[2] A. Irbäck, C. Peterson, F. Potthast, and O. Sommelius, J. Chem. Phys. 107, 273 (1997).

[3] H.-P. Hsu, V. Mehra, and P. Grassberger, e-print: cond-mat/0302545.