title: Carbonization of a stable β-sheet-rich silk protein into a pseudographitic pyroprotein.
abstract: Silk proteins are of great interest to the scientific community owing to their unique mechanical properties and interesting biological functionality. In addition, the silk proteins are not burned out following heating, rather they are transformed into a carbonaceous solid, pyroprotein; several studies have identified potential carbon precursors for state-of-the-art technologies. However, no mechanism for the carbonization of proteins has yet been reported. Here we examine the structural and chemical changes of silk proteins systematically at temperatures above the onset of thermal degradation. We find that the β-sheet structure is transformed into an sp(2)-hybridized carbon hexagonal structure by simple heating to 350 °C. The pseudographitic crystalline layers grew to form highly ordered graphitic structures following further heating to 2,800 °C. Our results provide a mechanism for the thermal transition of the protein and demonstrate a potential strategy for designing pyroproteins using a clean system with a catalyst-free aqueous wet process for in vivo applications.
authors.affiliation: Department of Polymer Science and Engineering, Inha University, Incheon 402-751, Korea.
authors.forename: Se Youn
authors.initials: SY
authors.lastname: Cho
authors.affiliation: Department of Polymer Science and Engineering, Inha University, Incheon 402-751, Korea.
authors.forename: Young Soo
authors.initials: YS
authors.lastname: Yun
authors.affiliation: 1] Carbon Convergence Materials Research Center, Korea Institute of Science and Technology, San 101 Enha-ri, Bongdong-eup, Wanju-gun 565-905, Korea [2] Department of Nano Material Engineering, Korea University of Science and Technology, 217 Gajeong-ro, Yusung-gu, Daejeon 305-350, Korea.
authors.forename: Sungho
authors.initials: S
authors.lastname: Lee
authors.affiliation: 1] Carbon Convergence Materials Research Center, Korea Institute of Science and Technology, San 101 Enha-ri, Bongdong-eup, Wanju-gun 565-905, Korea [2] Department of Nano Material Engineering, Korea University of Science and Technology, 217 Gajeong-ro, Yusung-gu, Daejeon 305-350, Korea.
authors.forename: Dawon
authors.initials: D
authors.lastname: Jang
authors.affiliation: Department of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea.
authors.forename: Kyu-Young
authors.initials: KY
authors.lastname: Park
authors.affiliation: Department of Physics, Incheon National University, Incheon 406-772, Korea.
authors.forename: Jae Kyung
authors.initials: JK
authors.lastname: Kim
authors.affiliation: Department of Physics, Incheon National University, Incheon 406-772, Korea.
authors.forename: Byung Hoon
authors.initials: BH
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea.
authors.forename: Kisuk
authors.initials: K
authors.lastname: Kang
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, Massachusetts 02155, US.
authors.forename: David L
authors.initials: DL
authors.lastname: Kaplan
authors.affiliation: Department of Polymer Science and Engineering, Inha University, Incheon 402-751, Korea.
authors.forename: Hyoung-Joon
authors.initials: HJ
authors.lastname: Jin
mesh_terms: D000818:Animals; D012831:Bombyx; D002152:Calorimetry, Differential Scanning; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D003460:Crystallization; D005349:Fibroins / Q000737:chemistry*; D006358:Hot Temperature; D008855:Microscopy, Electron, Scanning; D017433:Protein Structure, Secondary; D047011:Silk / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D047011:Silk; D002244:Carbon; D005349:Fibroins