Numerical study of a binary Yukawa model in regimes characteristic of globular proteins in solutions

Journal Article · Tue Mar 01 00:00:00 EST 2005 · Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics

DOI:https://doi.org/10.1103/PhysRevE.71.031108· OSTI ID:20641374

Giacometti, Achille; Gazzillo, Domenico; Pastore, Giorgio; Das, Tushar Kanti ^[1]

---

1. Istituto Nazionale per la Fisica della Materia and Dipartimento di Chimica Fisica, Universita di Venezia, S. Marta DD 2137, I-30123 Venice (Italy)

The main goal of this paper is to assess the limits of validity, in the regime of low concentration and strong Coulomb coupling (high molecular charges), of a simple perturbative approximation to the radial distribution functions (RDF's), based upon a low-density expansion of the potential of mean force and proposed to describe protein-protein interactions in a recent small-angle-scattering (SAS) experimental study. A highly simplified Yukawa (screened Coulomb) model of monomers and dimers of a charged globular protein ({beta}-lactoglobulin) in solution is considered. We test the accuracy of the RDF approximation, as a necessary complementary part of the previous experimental investigation, by comparison with the fluid structure predicted by approximate integral equations and exact Monte Carlo (MC) simulations. In the MC calculations, an Ewald construction for Yukawa potentials has been used to take into account the long-range part of the interactions in the weakly screened cases. Our results confirm that the perturbative first-order approximation is valid for this system even at strong Coulomb coupling, provided that the screening is not too weak (i.e., for Debye length smaller than monomer radius). A comparison of the MC results with integral equation calculations shows that both the hypernetted-chain (HNC) and Percus-Yevick closures have a satisfactory behavior under these regimes, with the HNC being superior throughout. The relevance of our findings for interpreting SAS results is also discussed.

• OSTI ID: 20641374
• Journal Information: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 71, Issue 3; Other Information: DOI: 10.1103/PhysRevE.71.031108; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-651X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCURACY
COMPARATIVE EVALUATIONS
DEBYE LENGTH
DIMERS
DISTRIBUTION FUNCTIONS
INTEGRAL EQUATIONS
MONOMERS
MONTE CARLO METHOD
NUMERICAL ANALYSIS
PERTURBATION THEORY
PROTEINS
SIMULATION
SMALL ANGLE SCATTERING
SOLUTIONS
SPATIAL DISTRIBUTION
YUKAWA POTENTIAL