title: Switchable wettability on cooperative dual-responsive poly-L-lysine surface.
abstract: A cooperative dual-responsive polypeptide surface switching between superhydrophilic and superhydrophobic states is presented. This macroscopic phenomenon of surface originates from the combination of the cooperative unfolding/aggregation of the poly-L-lysine (PLL) immobilized on the substrate with micro/nanocomposite structure in response to pH and temperature. At pH lower than the pK(a) of PLL (approximately 11.0), PLL mainly adopts a random coil conformation, which corresponds to the superhydrophilic state on the rough surface substrate. Raising the pH to higher than the pK(a) allows the appearance of alpha-helix conformation, which also corresponds to the hydrophilic state. However, heating up the surface at pH higher than the pK(a) destabilizes the alpha-helix conformation and induces the formation of aggregated beta-sheet structures, which represents the superhydrophobic state. Lowering the pH and temperature simultaneously switches a reversible conversion from superhydrophobic to superhydrophilic states. In the switching process, the hydrophobicity and hydrophilicity can be "memorized" due to the cooperative pH and temperature stimuli-induced unfolding/aggregation behaviors of PLL. This provides a new exciting prospect for understanding surface properties of polypeptides and the design of smart material surfaces with potential applications in nanodevices, bioseparation, and biosensors.
authors.affiliation: Key Laboratory of Surface and Interface Chemistry of Jilin Province, College of Chemistry, Jilin University, Changchun 130012, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Guo
authors.forename: Fan
authors.initials: F
authors.lastname: Xia
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Wensheng
authors.initials: W
authors.lastname: Yang
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang
mesh_terms: D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D008962:Models, Theoretical; D011107:Polylysine / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013499:Surface Properties; D013696:Temperature; D017155:Wettability
chemical_list: D011107:Polylysine