Electrostatic solvation energy for two oppositely charged ions in a solvated protein system: salt bridges can stabilize proteins.
Born-type electrostatic continuum methods have been an indispensable ingredient in a variety of implicit-solvent methods that reduce computational effort by orders of magnitude compared to explicit-solvent MD simulations and thus enable treatment using larger systems and/or longer times. An analysis of the limitations and failures of the Born approaches serves as a guide for fundamental improvements without diminishing the importance of prior works. One of the major limitations of the Born theory is the lack of a liquidlike description of the response of solvent dipoles to the electrostatic field of the solute and the changes therein, a feature contained in the continuum Langevin-Debye (LD) model applied here to investigate how Coulombic interactions depend on the location of charges relative to the protein/water boundary. This physically more realistic LD model is applied to study the stability of salt bridges. When compared head to head using the same (independently measurable) physical parameters (radii, dielectric constants, etc.), the LD model is in good agreement with observations, whereas the Born model is grossly in error. Our calculations also suggest that a salt bridge on the protein's surface can be stabilizing when the charge separation is < or =4 A.
Gong
Haipeng
H
MOE Key Lab of Bioinformatics, Institute of Bioinformatics and System Biology, School of Life Science, Tsinghua University, Beijing, China. hgong@tsinghua.edu.cn
Freed
Karl F
KF
D000465:Algorithms; D003198:Computer Simulation; D007477:Ions / Q000737:chemistry*; D008956:Models, Chemical; D055550:Protein Stability; D011506:Proteins / Q000737:chemistry*; D012492:Salts / Q000737:chemistry*; D055672:Static Electricity; D014867:Water / Q000737:chemistry
D007477:Ions; D011506:Proteins; D012492:Salts; D014867:Water