Eleven cases (a–k) of connectivity in conserved protein complexes from two different PPI networks, when parameters l and r are set to 2 and 3 in the course of extending a pair of homologous proteins. The nodes with different color come from different PPI networks. The full lines connecting two different color nodes represent their known homologous mappings. The dot lines represent artificial homologous mappings by a unbalanced Bi-random walk algorithm. The full lines connecting the same color nodes represent their interactions.