Carbon coated copper em grids

The purity and integrity of the VLPs were confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and negative-stain electron microscopy (EM), respectively. For the SDS-PAGE analysis, the samples were incubated with 1× Laemmli sample buffer (Bio-Rad, Hercules, CA, USA) with 2% β-mercaptoethanol and boiled for 5 min at 100 °C. The denatured VLPs were applied to a 10% polyacrylamide gel and ran at 80 V. The gel was washed three times with distilled water (diH₂O) and stained with GelCode blue protein stain (Invitrogen) for 30 min. The gel was de-stained with diH₂O prior to imaging using a GelDoc XR+ system (Bio-Rad). For negative stain EM, carbon-coated copper EM grids (Ted Pella, Redding, CA, USA) were incubated with 5 µl of 1:10 diluted sample for 1–5 min, washed with diH₂O, and stained with 2% uranyl acetate for 6 s. The grids were imaged on a Tecnai G2 Spirit TEM (FEI Co, Hillsboro, OR, USA) microscope operated at an accelerating voltage of 120 kV and micrographs were collected on a Gatan 2K × 2K CCD camera.

The purity and integrity of the VLPs were confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and negative-stain electron microscopy (EM), respectively. For the SDS-PAGE analysis, the samples were incubated with 1× Laemmle Sample Buffer (Bio-Rad, Hercules, CA, USA) with 10% β-mercaptoethanol and boiled for 10 min at 100 °C. The denatured proteins were applied to a 12% polyacrylamide gel and ran at 120 V. The gel was washed three times with distilled water (diH₂O) and stained with GelCode Blue Protein Safe stain (Invitrogen, Carlsbad, CA, USA) for 30 min. The gel was de-stained with diH₂O prior to imaging using a GelDoc EX system (Bio-Rad). For negative stain EM, carbon-coated copper EM grids (Ted Pella, Redding, CA, USA) were incubated with 5 µL of sample for 1–5 min, washed with diH₂O, and stained with Nano-W (Nanoprobes, Inc., Yaphank, NY, USA) for 30 s. The grids were imaged on a Tecnai G2 Spirit TEM (FEI Co., Hillsboro, OR, USA) microscope operated at an accelerating voltage of 120 kV and micrographs were collected on a Gatan 2 K × 2 K CCD camera (Gatan, Inc., Pleasanton, CA, USA).