title: Role of charge regulation and size polydispersity in nanoparticle encapsulation by viral coat proteins.
abstract: Nanoparticles can be encapsulated by virus coat proteins if their surfaces are functionalized to acquire a sufficiently large negative charge. A minimal surface charge is required to overcome (i) repulsive interactions between the positively charged RNA-binding domains on the proteins and (ii) the loss of mixing and translational entropy of RNA and capsid coat proteins. Here, we present a model describing the encapsulation of spherical particles bearing weakly acidic surface groups and investigate how charge regulation and size polydispersity impact upon the encapsulation efficiency of gold nanoparticles by model coat proteins. We show that the surface charge density of these particles cannot be assumed fixed, but that it adjusts itself to minimize electrostatic repulsion between the charges on them and maximize the attractive interaction with the RNA binding domains on the proteins. Charge regulation in combination with the natural variation of particle radii has a large effect on the encapsulation efficiency: it makes it much more gradual despite its inherently cooperative nature. Our calculations rationalize recent experimental observations on the coassembly of gold nanoparticles by brome mosaic virus coat proteins.
authors.affiliation: Faculteit Technische Natuurkunde, Technische Universiteit Eindhoven , Postbus 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Remy
authors.initials: R
authors.lastname: Kusters
authors.forename: Hsiang-Ku
authors.initials: HK
authors.lastname: Lin
authors.forename: Roya
authors.initials: R
authors.lastname: Zandi
authors.forename: Irina
authors.initials: I
authors.lastname: Tsvetkova
authors.forename: Bogdan
authors.initials: B
authors.lastname: Dragnea
authors.forename: Paul
authors.initials: P
authors.lastname: van der Schoot
mesh_terms: D017795:Bromovirus / Q000378:metabolism; D036022:Capsid Proteins / Q000737:chemistry* / Q000378:metabolism; D019277:Entropy; D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D008962:Models, Theoretical; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D055672:Static Electricity
chemical_list: D036022:Capsid Proteins; C430231:coat protein, Brome mosaic virus; D012313:RNA; D006046:Gold