title: Thermal and Structural Properties of Silk Biomaterials Plasticized by Glycerol.
abstract: The molecular interactions of silk materials plasticized using glycerol were studied, as these materials provide options for biodegradable and flexible protein-based systems. Plasticizer interactions with silk were analyzed by thermal, spectroscopic, and solid-state NMR analyses. Spectroscopic analysis implied that glycerol was hydrogen bonded to the peptide matrix, but may be displaced with polar solvents. Solid-state NMR indicated that glycerol induced β-sheet formation in the dried silk materials, but not to the extent of methanol treatment. Fast scanning calorimetry suggested that β-sheet crystal formation in silk-glycerol films appeared to be less organized than in the methanol treated silk films. We propose that glycerol may be simultaneously inducing and interfering with β-sheet formation in silk materials, causing some improper folding that results in less-organized silk II structures even after the glycerol is removed. This difference, along with trace residual glycerol, allows glycerol extracted silk materials to retain more flexibility than methanol processed versions.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Brown
authors.affiliation: School of Molecular Sciences and the Magnetic Resonance Research Center, Arizona State University , Tempe, Arizona 85287-1604, United States.
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Davidowski
authors.affiliation: School of Molecular Sciences and the Magnetic Resonance Research Center, Arizona State University , Tempe, Arizona 85287-1604, United States.
authors.forename: Dian
authors.initials: D
authors.lastname: Xu
authors.forename: Peggy
authors.initials: P
authors.lastname: Cebe
authors.affiliation: Department of Chemistry and Biochemistry, San Diego State University , 5500 Campanile Drive, San Diego, California 92182-1030, United States.
authors.forename: David
authors.initials: D
authors.lastname: Onofrei
authors.affiliation: Department of Chemistry and Biochemistry, San Diego State University , 5500 Campanile Drive, San Diego, California 92182-1030, United States.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Holland
authors.forename: David L
authors.initials: DL
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D012831:Bombyx / Q000378:metabolism*; D005349:Fibroins / Q000737:chemistry*; D005990:Glycerol / Q000737:chemistry*; D010968:Plasticizers / Q000737:chemistry*; D047011:Silk / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D010968:Plasticizers; D047011:Silk; D014867:Water; D005349:Fibroins; D005990:Glycerol