Self-assembly of precursors in single-crystal growth of biopolymers.

Self-assembly of precursors in dilute solution single-crystal growth of poly[(R)-3-hydroxyvalerate] (PHV) and the fungal polysaccharide mycodextran were studied by transmission electron microscopy, especially at the early stages of crystallization. Precursors for PHV, such as small primary nuclei and tiny square tiles, consolidate to a large square crystal composed of orthogonally arranged tiles. By contrast, the precursors of mycodextran were lath-shaped, which suggests that the crystal growth is mainly in the longitudinal direction. Needlelike precursors were observed either free or as protrusions at the lath ends. In general, single-crystal shape and morphology are dependent on the type of precursor and on the manner of crystallization.