Table 1.

Labeling Efficiency of Influenza Virus with R18 or Texas Red

R18 Labeling Solution	R18 Mean Dyes per Virion	Texas Red Labeling Solution	Texas Red Mean Dyes per Virion
10 μg/mL	1900	15 μg/mL	940
20 μg/mL	5100	25 μg/mL	5500
30 μg/mL	6800	35 μg/mL	8000
40 μg/mL	7100	–	–

At low dye concentrations, there is a supralinear increase in labeling with dye concentration; this becomes linear in the 20–35 μg/mL region for both dyes and begins to saturate at 40 μg/mL for R18.