Figure S1. Blue shift and increase in the intensity of fluorescence were observed when N-phenyl-1-naphthylamine (1-NPN) was bound to AlinOBP13. 1-NPN was dissolved in methanol and added to 50 mM Tris buffer (pH 7.4) at 5 μM, and the protein AlinOBP13 was also at 5 μM. When excited at 337 nm, 1-NPN in the Tris buffer produces a fluorescence peak with its maximum 450 nm, but in the presence of AlinOBP13, the emission wavelength is shifted to 405 nm accompanied by a sixfold increase in the intensity.


Figure S2. Binding curves and Scatchard plots (insert) of the fluorescence probe N-phenyl-1-naphthylamine (1-NPN) to AlinOBP13. The dissociation constant of the AlinOBP13/1-NPN complex was 8.99 ± 0.90 μM.


Figure S3. Binding curves and Scatchard plots for N-phenyl-1-naphthylamine (1-NPN) to the recombinant AlinOBP13 at three pH values (5.0, 7.4 and 10.0).


Figure S4. Effect of sodium ion concentrations (0, 30, and 60 mM) on the binding affinities of AlinOBP13 to β-caryophyllene and trans-β-farnesene at pH 7.4.


Figure S5. Comparison of binding abilities (1/Ki) of two other insect OBPs with their ligands at pH 7.4 and 10.0. Binding activity of AlinOBP11 to nerolidol and binding activity of HarmPBP1 to Z11–16:ALD.


Figure S6. Predicted three-dimensional mode of AlinOBP13. Helices, N-terminal (N), and C-terminal (C) were labelled, and disulphide bridges were labelled yellow. Some hydrophobic and hydrophilic residues predicted as putative binding sites were displayed with green sticks.


Table S1. Primers used in quantitative reverse transcriptase PCR and recombinant AlinOBP13 prokaryotic expression.

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