SDS–PAGE analysis of crystals of WNV NS2B–NS3. Lane 1, molecular-weight markers; lane 2, freshly prepared WNV NS2B–NS3; lanes 3 and 4, crystals of nontreated protein; lanes 5 and 6, crystals of trypsin-digested protein; lanes 7 and 8, crystals of 18 h digested protein; lanes 9 and 10, crystals of 90 h digested protein.