Adeola O. Sadik1, Christoph Walkner2, Shengli Ma3, Laurence Nafie3, and Teresa Freedman3. (1) University of Pittsburgh, Pittsburgh, PA, (2) University of Technology Graz, Graz, Austria, (3) Syracuse University, Syracuse, NY
Amyloid fibrils formed from insulin and lysozyme were found to produce large vibrational circular dichroism (VCD) spectra. The fibrils were synthesized using a combination of high heat, low pH, and high ionic strength. Insulin fibrils were formed after an incubation period of two hours at pH 2 and 60 °C. Lysozyme fibrils were formed after an incubation period of twelve days at pH 2 and 57 °C. Using VCD, both static spectra and dynamic changes in spectra were observed. The dynamic time-course showed VCD and IR spectra changing from that of the native insulin to the pre-fibril and the mature fibril with a 50-fold increase in VCD intensity. Continuous characterization also showed a regression of the pre-fibril back into the native form upon cooling and further fibril formation upon heating. Fibril formation was also verified with Congo red binding assays. The goal of the work was to identify VCD features in the amide I (C=O stretch) and amide II (NH deformation) regions that characterize the process of fibril formation from the native protein structure.
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