The 3-dimensional arrangement of factor VIII domains in relationship to a phospholipid membrane. The factor VIII molecule on the left has been rotated ∼60° back from its membrane-binding angle. Amino acid clusters that participate in membrane binding, demonstrated by mutagenesis experiments, are orange. The location of the neoclassical antibody G99 is depicted as magenta, identifying a thrombin and factor Xa interactive site. The epitope for the classical inhibitory antibody 3E6 is yellow. Professional illustration by Alice Y. Chen.