In solution digests of purified virions. For analysis of purified CYDV-RPV virions in solution, disulfide bonds were reduced with 5 mM dithiothreitol (DTT) for 30 min, followed by alkylation with 10 mM iodoacetamide (IAA) for 30 min, in the dark. Reduction and alkylation were performed at 25uC. CYDV-RPV virions were then digested with trypsin (1:200 ratio, Promega) at 35uC for 16 h. The peptide mixture was desalted using a C18 sep-pak (Waters) and stored at 280uC for 1 week prior to MS analysis.