Packing (stacking) arrangement of the M1 molecules (in ribbon diagrams). Monomers A and B are colored grey and orange, respectively.

<p><b>A.</b> A dimer of 1AA7 stacked on top of another dimer to form a pseudo-tetramer. A similar arrangement is observed in 3MD2. <b>B.</b> A pseudo-tetramer appears to form similarly in 4PUS, however, the two stacked dimers do not interact with each other. <b>C.</b> Arrangement of monomers in 1EA3 to form a pseudo-tetramer.