Some cephalopods (squids, octopuses, and cuttlefishes) produce dynamic structural colors, for camouflage or communication. The key to this remarkable capability is one group of specialized cells called iridocytes, which contain aligned membrane-enclosed platelets of high-reflective reflectins and work as intracellular Bragg reflectors. These reflectins have unusual amino acid compositions and sequential properties, which endows them with functional characteristics: an extremely high reflective index among natural proteins and the ability to answer various environmental stimuli. Based on their unique material composition and responsive self-organization properties, the material community has developed an impressive array of reflectin- or iridocyte-inspired optical systems with distinct tunable reflectance according to a series of internal and external factors. More recently, scientists have made creative attempts to engineer mammalian cells to explore the function potentials of reflectin proteins as well as their working mechanism in the cellular environment. Progress in wide scientific areas (biophysics, genomics, gene editing, etc.) brings in new opportunities to better understand reflectins and new approaches to fully utilize them. The work introduced the composition features, biochemical properties, the latest developments, future considerations of reflectins, and their inspiration applications to give newcomers a comprehensive understanding and mutually exchanged knowledge from different communities (e.g., biology and material).

Proteins, as gifts from nature, provide structure, sequence, and function templates for designing biomaterials. Here, we reported an engineered toolkit derived from a natural block copolymer, RfA1. RfA1 is composed of positively charged polyelectrolyte linker regions interspersed with highly conserved polyampholyte motifs. These linkers and motifs are constructional fragments and ready-to-use building blocks for synthetic design and construction. One functional and editable feature of RfA1 derivatives is their preferential distribution to cytoplasm or nucleoplasm, in a fragment-replication-determined manner. Based on this property, a prices spatiotemporal Tet-on demo was established, which effectively transports cargo peptides into nuclei at selective time points. Moreover, the functional homogeneities of either motifs or linkers were also verified, making them standardized building blocks for synthetic biology. In summary, this study provides a modularized, orthotropic and well-characterized toolkit for precise and spatiotemporal regulation of protein nucleocytoplasmic localization.

Based on the pre-screened functional derivative peptide Bal cp20k-P3 (P3), this study systematically clarifies its environmental responsive mechanisms and biomedical functions via multi-scale characterization analysis.