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Biophysics Research

Areas of interest:
  • Silk-Inspired Di-Block Copolymers
  • Crystallization of Beta Sheets in Silk Fibroin Films
  • Liquid Crystalline Phase Structure in Collagen-Model Peptides

The Cebe research group has active collaborations with the Biomedical Engineering Department (with Profs. David Kaplan and Irene Georgekoudi), and the Tufts Medical School Department of Biochemistry. These collaborations involved sharing of research projects, laboratory space, facilities and equipment, intellectual exchange through jointly held group meetings, and co-publication of research results. Through our collaborative efforts we have been successful in bringing several large instruments to Tufts, including a Brookhaven laser light scattering system, two Bruker AXS X-ray diffractometers, Woollam variable angle spectroscopic ellipsometer, and a Langmuir-Blodgett trough. We also have been awarded an NSF equipment grant for a suite of thermal analysis instrumentation including: TA Instruments differential scanning calorimeter, thermogravimetric analyzer, shear rheometer, and dynamic mechanical analyzer.

We are presently working in two areas of biophysics research: structure and dynamics of silk proteins, and spider silk inspired di-block copolymers. In the first project, the kinetics of silk beta sheet formation is studied using temperature-modulated differential scanning calorimetry, FTIR, and wide angle X-ray diffraction. Real-time X-ray studies of the crystallization process of silk fibroin have been performed at the Brookhaven National Synchrotron Light Source. The thermal and X-ray methods allow the time development of beta sheets to be assessed. The crystallization of beta sheets results in a change in the glass transition temperature and the heat capacity increment at the glass transition of the silk fibroin. FTIR analysis is used to quantify the fraction of beta-sheets, random coil, or beta-turn structures present in the sample of silk fibroin before and after crystallization.

Wenwen Huang at FTIR
Former graduate student, Dr. Wenwen Huang, uses the Fourier transform infrared spectrometer to investigate phase behavior of silk-inspired di-block copolymers.
Xiao with poster
Former graduate student, Dr. Xiao Hu, is now a professor at Rowan University. He poses in front of his poster, presented at the Fall 2006 meeting of the Materials Research Society.
FTIR silk
The infrared absorbance vs. frequency is snown during crystallization of B. mori silk fibroin, at 200º C for 60 min. Amide I region indicates the increase of beta sheets, and decrease of random coils and turns, during crystallization. Amide II region shows no changes.
Xiao with poster
Undergraduate physics major, Isabel Yannatos, uses the polarizing optical microscope to study orientation of collagen films and fibers.

The second project goal is to generate a new family of silk-based block copolymers to understand and then control morphological and structural features generated via self-assembly. We anticipate that the use of silk designs as inspiration will provide important materials, while in the longer term these proteins will also serve as a model system upon which to design and implement new synthetic polymer strategies. We use precise control over polymer chemistry, polymer block design and self-assembly, to provide a new generation of functional materials. Our model system consists of protein sequences found in native spider dragline silk and we use genetic variants of these sequences to provide the copolymer building blocks and components in order to assess relationships between block sequence and morphological and structural features.

This program is funded by the National Science Foundation through the Biotechnology Program of the Division of Chemical, Bioengineering, Environmental, and Transport Systems, CBET-0828028, and MRI Program under DMR-0520655 for thermal analysis instrumentation; formerly through the Polymers Program of the Division of Materials Research, grant DMR-0402849 and NASA grant NAG8-1921 and a Tufts University Faculty Research Award.