Table 2.

Biophysical properties of the β-barrel proteins used in this study.⁶⁷

Proteina	pI/Charge state	GRAVYc	Aliphatic indexd	Negative residues	Positive residues	Total number of residuese
WT-OmpG	4.4/acidic	−0.798	55.87	55	22	281
FhuA ΔC/Δ5Lb	5.7/acidic	−0.550	60.42	57	48	505
FhuA ΔC/Δ5L_25N	9.3/basic	−0.563	58.31	34	43	473
FhuA ΔC/Δ7L_30N	9.6/basic	−0.574	57.42	27	42	426

^aAll proteins have a 6His⁺ tag at the C terminus.

^bThis engineered FhuA includes a 33-residue signal peptide at the N terminus.

^cThe GRAVY hydrophobicity parameter was calculated by adding individual hydropathy indexes⁶⁸ of each residue and dividing by the total number of residues. Increasing positive GRAVY number shows a more hydrophobic protein.

^dThe aliphatic index is given by the relative volume of aliphatic chain-containing residues.⁶⁹

^eThe total number of residues includes those amino acids from the Gly/Ser-rich containing polypeptide loop and 6×His⁺ tag.