Fig. 1 | Nature Communications

Fig. 1

From: Electro-osmotic capture and ionic discrimination of peptide and protein biomarkers with FraC nanopores

Fig. 1

Capture of endothelin 1 and chymotrypsin with two FraC variants at two different pH conditions. a Cross sections of wild-type FraC (WtFraC, PDB: 4TSY) and D10R-K159E-FraC (ReFraC). b, c Representative traces induced by 1 µM endothelin 1 (b) and 200 nM chymotrypsin (c) to WtFraC (left) and ReFraC (right). Chymotrypsin (PDB: 5CHA) and human endothelin 1 (PDB: 1EDN) are shown as surface representations. Endothelin 1 and chymotrypsin enter WtFraC under negative applied potentials, while they enter ReFraC under positive applied potentials. Chymotrypsin blockades to WtFraC were also observed under −50 mV at pH 7.5 and 4.5; however, the applied potential was increased to −100 mV to obtain a sufficient number of blockades. At pH 7.5, blockades to ReFraC by chymotrypsin under positive applied bias required higher potential than to WtFraC under negative applied bias. The buffer at pH 7.5 included 1 M KCl, 15 mM Tris base, and the buffer at pH 4.5 contained 1 M KCl, 0.1 M citric acid, 180 mM Tris base. Endothelin 1 and chymotrypsin were added into cis compartment. All traces were recorded using 50 kHz sampling rate and a 10 kHz low-pass Bessel filter. The coloring represents the electrostatic potential of the molecular surface as calculated by APBS75 (pH 7.5 in 1 M KCl) with red and blue corresponding to negative and positive potentials (range from −4 to +4 k B T/e c ), respectively. Structures were rendered using PyMOL

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