The Trapping of Tymovirus Particles on Electron Microscope Grids by Adsorption and Serological Binding

Abstract

Many purified tymovirus particles are trapped on buffer-treated grids due to non-specific adsorption. Pre-treatment of grids with serum or addition of crude plant sap to virus preparations greatly inhibited non-specific adsorption. Specific serological binding on grids coated with homologous antiserum produced particle counts comparable to those achieved by non-specific adsorption on buffer-treated grids in the absence of plant sap. Specific serological binding was not influenced by crude sap of Nicotiana clevelandii. For both adsorption and serological binding there was a linear relationship between the log virus concentration and log particle counts at virus concentrations below approx. 10 µg/ml; at higher concentrations the grids were saturated. In the presence of excess virus, antisera at dilutions of less than 10^-3 yielded lower particle counts than more dilute antisera. Heterologous reactions were detected only with viruses for which very close serological relationships had been found in the agar gel double-diffusion test. Heterologously bound virus was apparently not replaced by subsequently applied homologous virus. However, adsorbed bottom component virus particles could be replaced by top component particles of the same virus and vice versa.