FIG. 4.

Fusion of R18-labelled ISAV with liposomes. Liposomes were diluted to a lipid concentration of 0.3 mM in the three different buffers mentioned in “Preparation of liposomes.” The solution (90 μl) was added to a cuvette containing 10 μl (1.4 mg of viral protein/ml) of R18-labelled ISAV. The increase in rhodamine fluorescence was measured with a Perkin-Elmer LS50B luminescence spectrometer (excitation [Ex], 560 nm; emission [Em], 590 nm). Each sample was assayed three times, and the average intensity values were plotted against time.