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Effect of the Surface Charge Distribution on the Fluid Phase Behavior of Charged Colloids and Proteins



Marco A. Blanco Medina, Vincent K. Shen


A generic but simple model is presented to evaluate the eft ect of the heterogeneous surface charge distribution of proteins and zwitterionic nanoparticles on their rich thermodynamic phase behavior. By considering surface charges as continuous "patches", the rich set of surface patterns that is embedded in proteins and charged patchy particles can readily be described. This model is used to study the fluid phase separation of charged particles where the screening length is of the same order of magnitude than the molecular/particle size. In particular, two type of charged particles are studied: dipolar fluids and protein-like fluids. The former represents the simplest case of zwitterionic particles, whose charge distribution can be described by the dipole moment. The latter system corresponds to molecules/particles with complex surface charge arrangements such as those in biomolecules. The results for both systems suggest a relation between the critical region, the strength of the interparticle interactions, and the dispersion of charged patches, where the critical temperature is strongly correlated to the magnitude of the dipole moment. Additionally, competition between attractive and repulsive charge-charge interactions seems to be related to the formation of transient clusters along the dilute phase in dipolar fluids, as well as to the broadening of the binodal curve in protein-like fluids. Finally, a variety of self-assembled architectures are detected for dipolar fluids upon small changes in the charge distribution, providing the groundwork for studying the self-assembly of charged patchy particles.
Journal of Chemical Physics


protein phase separation, patchy particles, self-assembly, charge distribution, charged colloids


Blanco, M. and Shen, V. (2016), Effect of the Surface Charge Distribution on the Fluid Phase Behavior of Charged Colloids and Proteins, Journal of Chemical Physics, [online], (Accessed July 17, 2024)


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Created October 21, 2016, Updated November 10, 2018