Impact of Charge Variation on the Encapsulation of Nanoparticles by Virus Coat Proteins

TL;DR

This paper models how charge variations affect nanoparticle encapsulation by virus coat proteins, explaining experimental results through electrostatic interactions and a mass action law.

Contribution

It introduces a simple electrostatic model combined with a mass action law to quantitatively explain nanoparticle encapsulation behavior.

Findings

Model agrees with experimental data

Charge distribution influences encapsulation efficiency

Encapsulation is a gradual function of surface charge density

Abstract

Electrostatic interaction is the driving force for the encapsulation by virus coat proteins of nanoparticles such as quantum dots, gold particles and magnetic beads for, e.g., imaging and therapeutic purposes. In recent experimental work, Daniel et al. [ACS Nano 4 (2010), 3853-3860] found the encapsulation efficiency to sensitively depend on the interplay between the surface charge density of negatively charged gold nanoparticles and the number of positive charges on the RNA binding domains of the proteins. Surprisingly, these experiments reveal that despite the highly cooperative nature of the co-assembly at low pH, the efficiency of encapsulation is a gradual function of their surface charge density. We present a simple all-or-nothing mass action law combined with an electrostatic interaction model to explain the experiments. We find quantitative agreement with experimental observations, supporting the existence of a natural statistical charge distribution between nanoparticles.