Figure 3.

Stability of NA enzyme activity after incubation at 37°C in different buffers. Samples of wild-type and mutant Y155H virus were incubated at 37°C in (a) PBS, (b) TBS, (c) MES and (d) MM. Enzyme activity was determined in the MUNANA assay after 30, 60 and 90 min and the remaining activity was expressed as a percentage of that of the control sample assayed at 0 min. Values are based on the means of triplicate samples. The Y155H NA was much more unstable in all buffers and with CHAPS detergent compared with the wild-type. CaCl₂ stabilized the activity in all buffers.