Thermal Behavior of Silk Protein

P. Cebe1, D. Thomas1, J. Merfeld1, B. P. Parlow2, D. L. Kaplan2, R. Alamo3, A. Wurm4, E. Zhuravlev4, and C. Schick4

1Physics and Astronomy Dept., Tufts University, Medford, MA 02155 USA
2Biomedical Engineering Dept., Tufts University, Medford, MA 02155 USA
3Chemical and Biomedical Engineering Dept., Florida State University-FAMU, Tallahassee, FL 32310 USA
4 Institute for Physics and Competence Center Calorimetry of Interdisciplinary Faculty, University of Rostock, Rostock, Germany

Silk is a naturally occurring biopolymer which has been used in textiles for over 5000 years. Silk stands as an exemplar of the class of fibrous proteins. The properties of silk protein are related to its semicrystalline nature, imparted by the secondary structures, such as the non-crystalline helices and random coils, and the crystalline beta pleated sheets. Using techniques of condensed matter polymer physics, we investigate the structure and thermal behavior of silk fibroin [1-3]. We have prepared fibroin by extracting it from the native cocoons and use this as a starting material for our investigations into the structure and properties of silk. In this presentation, I will describe our studies to quantify the amounts of the different secondary structures using X-ray diffraction, infrared spectroscopy, and high precision, high accuracy heat capacity measurements [1]. Silk degrades before melting when heated at slow rates. We used fast scanning chip-based calorimetry to heat silk at 2000 K/s, thereby minimizing thermal degradation and demonstrating the melting behavior of beta pleated sheet crystals [2, 3].

[1] X. Hu, D. Kaplan, and P. Cebe, Macromolecules, 39, 6161 (2006). (link)
[2] P. Cebe, X. Hu, D. Kaplan, E. Zhuravlev, A. Wurm, D. Arbeiter, C. Schick. Scientific Reports, 3, 1130 (2013). (link)
[3] P. Cebe, B. P. Partlow, D. L. Kaplan, A. Wurm, E. Zhuravlev, C. Schick. Thermochimica Acta, 615, 8 (2015). (link)

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