Spacer 18 phosphoramidite

All reagents used for the synthesis of the FNA tether were purchased from Glen Research (Sterling, VA): spacer 18 phosphoramidite (18-O Dimethoxytritylhexaethyleneglycol, 1-[(2-cyanoethyl)-(N,N-diisopropyl)]-phosphoramidite, 10–1918, Glen Research), DBCO-dT-CE phosphoramidite (5′-Dimethoxytrityl-5-[(6-oxo-6-(dibenzo[b,f]azacyclooct-4-yn-1-yl)-capramido-N-hex-6-yl)-3-acrylimido]-2′-deoxy-Uridine, 3′-[(2-cyanoethyl)-(N,N-diisopropyl)]-phosphoramidite, 10-1539-xx, Glen Research), Thiol-Modifier C6 S-S, (1-O-Dimethoxytrityl-hexyl-disulfide,1′-[(2-cyanoethyl)-(N,N-diisopropyl)]-phosphoramidite, 10-1936-xx, Glen Research), biotin CPG (3′-Protected Biotin Serinol CPG; #20-2993; GlenResearch). The azide-labeled Aβ(14–23) peptide [K(N3)HQKLVFFVAED] was synthesized and purified by Peptide 2.0 company (VA, USA). Tris (2-carboxyethyl) phosphine (TCEP) hydrochloride was from Hampton Research (Aliso Viejo, CA). Heterobifunctional MAL-PEG₃₄₀₀-SVA was from Laysan Bio (Arab, AL). N-(g-Maleimidobutyryloxysuccinimide ester) GMBS was from Pierce Biotechnology (Grand Island, NY). Streptavidin-thiol was from Protein Mods (Madison, WI) and 1-(3-aminopropyl) silatrane (APS) was synthesized as previously described [15 (link)]. All other reagents or solvents were purchased from Sigma–Aldrich.