Enzyme-Directed Assembly of Antiparallel Cellulose II Nanocrystals: Unraveling the Mechanism Beyond Spontaneous Crystallization

Humans have long utilized cellulose II, known as regenerated cellulose, for fibers like rayon and Cupra and films like cellophane. While cellulose I, found in nature, consists of parallel molecular chains, cellulose II is characterized by the stable arrangement of molecules in an antiparallel orientation. Enzymatic synthesis of cellulose <i>in vitro</i> also affords cellulose II with various morphologies, from monolayer lamellae crystals to gels, but its formation mechanism remains obscure. Here, we demonstrate that cellodextrin phosphorylase (CDP) catalyzes the synthesis and orchestrates the antiparallel self-assembly of cellulose II nanocrystals, exceeding the paradigm of spontaneous crystallization. High-resolution structural analysis reveals CDP's key role in dictating crystal size and alignment, bridging the gap between enzymatic catalysis and biodirected material architecture. Our research unveils a unique protein-templated assembly process for advanced cellulose materials, paving the way for enzyme-guided construction of next-generation functional nanostructures.