Detergent-stripped immature HIV-1 virus-like particle purification. (A) Coomassie blue staining of SDS-PAGE of immature VLP before detergent treatment. (B) Coomassie blue staining of SDS-PAGE of immature particles after detergent treatment. Pr55 Gag and bovine serum albumin (BSA) are indicated by the arrows. Volumes of particle sample and nanograms of BSA standards are given at the top.