Fig. 5. Schematic diagram of the polymorphism of α-syn fibrils induced by heparin.

a Charge interactions of heparin with lysine residues that are buried inside the polymorphs 2a/2b fold block α-syn folds into polymorphs 2a/2b. Instead, α-syn forms a distinctive fold in complex with heparin. b Heparin disrupts the charge interactions between the protofilaments, which results in polymorphs either containing a single protofilament, or forming an interface mediated by heparin.