New method to quantify hydrophobicity of non-enveloped virions in aqueous media by capillary zone electrophoresis.

The hydrophobicity of virions is a major physicochemical parameter regulating their dissemination in humans and the environment. But knowledge about potential factors modulating virion hydrophobicity is limited due to the lack of suitable quantifying methods. It has been recently shown that sodium dodecyl-sulfate (SDS) labels capsid hydrophobic domains in capillary zone electrophoresis of non-enveloped virions, altering their electrophoretic mobility (μ) in proportion to their hydrophobicity. This was exploited here to quantify the hydrophobicity of GA, Qβ and MS2 phages as a function of pH. By subtracting the native from the SDS-modified μ of phages, measured in the absence and presence of SDS, respectively, we defined a "hydrophobic index" increasing with virion hydrophobicity. Using this approach, we found that the virion hydrophobicity changes at a virion-specific pivotal pH. This procedure may be applied under various physicochemical conditions and to diverse non-enveloped virus families of significance to human health and the environment.