The RNA core weakly influences the interactions of the bacteriophage MS2 at key environmental interfaces

Abstract

The effect of the RNA core on interfacial interactions of the bacteriophage MS2 was investigated. After removal of the RNA core, empty intact capsids were characterized and compared to untreated MS2. Electron density of untreated MS2 and RNA-free MS2 were characterized by transmission electron microscopy (TEM) and synchrotron-based small angle spectroscopy (SAXS). Suspensions of both particles exhibited similar electrophoretic mobility across a range of pH values. Similar effects were observed at pH 5.9 across a range of NaCl or CaCl₂ concentrations. We compared key interfacial interactions (particle–particle and particle/air–water interface) between suspensions of each type of particle using time resolved dynamic light scattering (TR-DLS) to observe and quantify aggregation kinetics and axisymmetric drop shape analysis to measure adsorption at the air–water interface. Both suspensions showed insignificant aggregation over 4 h in 600 mM NaCl solutions. In the presence of Ca²⁺ ions, aggregation of both types of particles was consistent with earlier aggregation studies and was characterized by both reaction-limited and diffusion-limited regimes occurring at similar [Ca²⁺]. However, the removal of the RNA from MS2 had no apparent effect on the aggregation kinetics of particles. Despite some differences in the kinetics of adsorption to the air–water interface, the changes in surface tension which result from particle adsorption showed no difference between the untreated MS2 and RNA-free MS2. The interactions and structure of particles at the air–water interface were further probed using interfacial dilational rheology. The surface elasticity (E_s) and surface viscosity (η_s) at the interface were low for both the untreated virus and the RNA-free capsid. This observation suggests that the factors that impact the adsorption kinetics are not important for an equilibrated interface.