Thermal stability and effect of cations on PgD5 activity. (A) Temperature stability of PgD5. After heat treatment, the remaining antifungal activity of PgD5 was scored against the control without heat treatment (25°C). (B) Effect of the presence of monovalent and divalent cations on PgD5 activity. The antifungal activity of PgD5 (at the dose of 2 μg/mL) was scored against V. dahliae by incubating the peptide in the presence of various concentrations of monovalent and divalent cations. The control was treated in the absence of cations in the medium.