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We examined liquid crystalline phases of the cytoskeletal polyelectrolyte filamentous (F-) actin in the presence of multivalent counterions. As a function of increasing ion concentration, the F-actin rods in either an isotropic or a nematic phase will transform into a new and unexpected lamellar phase of cross-linked rafts (Lₗₑ phase), before condensing into a bundled phase of parallel, close-packed rods. This behavior is generic for alkali earth divalent ions Mg^2+, Ca^2+, Sr^2+, and Ba^2+, and the structural transitions are achieved without any architecture-specific actin-binding linker proteins.
Wong et al. (Wed,) studied this question.