Selecting active threshold significantly influence the prediction precision of essential proteins. Apparently, the reliability of the dynamic PPI network evidently increases with increasing active threshold. As shown in Table 1, the average GO similarity of the dynamic PPI network increases with increasing active threshold. However, higher active threshold means fewer proteins and fewer essential proteins contained in the dynamic PPI network (Fig.1). The amount of proteins and essential proteins in the dynamic PPI network slowly decreases when the active threshold increases from 0 to 0.8 but rapidly decreases when the active threshold increases from 0.8 to 0.99. This result indicates that 0.8 is a demarcationpoint. Moreover, the dynamic PPI network still contains more than 93% of essential proteins inthestaticPPI networkwhenthe active threshold is 0.8. Therefore,the active threshold is setto 0.8 for the construction of a relatively reliable dynamic PPI network with enough proteins. This relatively high threshold is in accordance with what has been pointed out by Wang et al. (2013) that for each protein, the time points with its highest expression value and with expression value near to the highest one should be regarded as its active time points