Experimental evidence for a chiral symmetry-breaking mechanism in aspartic acid: Lattice and sub-lattice matching

A mother crystal formed from a transient molecular structure of (d+l) aspartic acid in solution is reported. Hexagonal structures with a lattice constant of 1.04 nm were crystallized from a solution in which three aspartic acid species coexist: right- and left-handed enantiomorphs, denoted d-aspartic and l-aspartic, respectively, and transitory (d+l) aspartic acid specie. Atomic force microscopy images of the crystalline deposits reveal domains of the transitory (d+l) aspartic acid crystal forming the substrate deposit on silicon wafers, and on top of this hexagonal lattice only l-aspartic acid is observed to conform and crystallize. A preferential crystallization mechanism is then observed for (d+l) aspartic acid crystals that seed only l-aspartic deposits by the geometrical matching of their multiple hexagonal lattice structures with periodicities of 1.04 nm and 0.52 nm, respectively.