Physiochemical Constraints in Influenza A Hemagglutinin

Influenza A viruses are negative-strand RNA viruses. The gene of hemagglutinin (HA) protein in the virus genome is the major molecule that determines the range of hosts. Mutation of HA gene may bring infection cross species. In this paper, we studied physicochemical constraints during the variations of HA gene. Fuzzy measure and Choquet integral were used to estimate the combining effect of different physicochemical properties for single residue in HA protein that related to infective events. With this method, an HA sequence was quantified residue by residue and produced a series of values. Finally, the Hurst exponent was adopted to infer the constraints in the series. We found that the physicochemical constraints in HA sequences mainly falling into two classes of interdependence strength during gene variation, that was distinct from the diversity of clusters in the phylogenetic analysis.