The SRCD spectrum of the toxin at 25 °C displays a large negative peak at 207 nm (Fig. 4), which matches the previously-reported CD spectrum of Bj-xtrIT [9], plus an additional positive peak at 190 nm with a shoulder at 185 nm (not seen previously as that study had used conventional CD spectroscopy). The estimate of the secondary structural content from the SRCD data was 25% α-helix, 23% β-sheet and 52% other structures, very similar to the content determined from the crystal structure of Bj-xtrIT (PDB ID: 1BCG), calculated using the 2Struc server (26% α-helix, 20% β-sheet and 54% other)