The beads were then washed thrice with 200 μL AV binding buffer as described above. The bead-captured membrane vesicles were then analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), ELISA, antibody array, and mass spectrometry. The beads were boiled in 28 μL of a standard denaturing/reducing SDS-PAGE loading buffer and resolved on 4-12% SDS–polyacrylamide gels. To assay for membrane proteins such as CD9, the beads were incubated with 1:500 dilution of mouse antihuman CD9

antibody (Santa Cruz Biotechnology, Santa Cruz, CA) with rotation for 30 minutes. The beads were then immobilized and supernatant was removed, washed thrice with 200 μL wash buffer, and then incubated with 1: 5000 HRP conjugated donkey antimouse IgG antibody (Santa Cruz Biotechnology) for CFTR activator 30 minutes with rotation at room temperature. After washing, the beads were incubated with 100 μL Amplex Red Substrate (Life Technologies) for 30 minutes and fluorescent intensity was measured at 530/590 ƞm (excitation/emission). To assay for luminal this website proteins, the bound vesicles are lysed with 100 μL of cell lysis buffer

(Biovision). The lysed vesicles were then biotinylated by adding 10 μL 1:4000 diluted 10 mM Sulfo-NHS Biotin (Thermo Scientific, #21217). To assay for CD9, soluble fms-like tyrosine kinase-1, brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP), placenta growth factor (PlGF), magnetic bead conjugated antibody specific for the protein of interest was then added. The antibody-bound protein was then immobilized by magnet and washed thrice as described above.

The target protein was assayed using Amplex Ultra Red Substrate as described earlier. For antibody array, CTB- and AV- vesicles were isolated from each of 6 PE patients and 6 healthy controls by incubating 30 μL of plasma with 1.5 ƞg biotinylated CTB or AV, respectively. The isolated vesicles were lysed as described previously and analyzed for proteins using RayBio Custom Quantibody Array (cat. QAH-CUST) according to manufacturer’s instructions (RayBiotech, Norcross, GA). For mass spectrometry, 300 μL of pooled plasma from either 6 PE patients or 6 healthy controls was incubated with 15 ng CTB either or AV to isolate CTB- and AV- vesicles. The 60 μL of the washed beads prepared as described above were then added to the plasma-CTB or plasma-AV reaction mix and incubated with rotation for 30 minutes. The beads were immobilized with a magnet and the supernatant was removed. The beads were then washed thrice with 200 μL AV binding buffer as described above. The isolated vesicles were lysed and resolved on a protein gel. Each gel lane was sliced separately into 8 pieces. The gel pieces were destained; proteins in the gel were reduced by 10 M dithiothreitol at 56°C for 1 hour and alkylated by 55 mM iodoacetamide for 45 minutes in the dark at room temperature. Tryptic digestion was performed by using porcine trypsin (Sequencing Grade Modified, Promega, WI) overnight.