Crystal structure of insulin (PDB ID: 9INS) [68] with 90° rotation.

Dark colored (blue) element corresponds to chain-A and light colored (green) to chain-B of insulin in the central structures. The three disulfide bond of insulin have been shown by solid arrows. The dotted arrows indicate the N- and C-terminal segments of chain-B. The dotted spheres on the left hand side of the figure show the central hydrophobic core of insulin. The surface potential of insulin molecule (blue - positive; red – negative) obtained after processing by PDB2PQR [69] and APBS [70] has been shown on the right hand side of the figure. The proposed model of insulin fibrillation is depicted at the bottom of the figure (see text for details).