FIG. 7.
Comparison of 22L, Chandler, and 87V PrPSc by infrared spectroscopy. Second-derivative Fourier transform IR spectra are shown for PK-treated PrPSc samples isolated from the brains of mice affected by either 22L, Chandler, or 87V scrapie. Spectral differences, especially in the β-sheet region of the spectrum, provide evidence that PrPSc proteins associated with these murine-adapted scrapie strains have distinct conformations. For comparison, a highly α-helical protein, hemoglobin, gives strong absorbance (represented by a negative deflection) at ∼1,657 cm−1, with only minor absorbance in the β-sheet region. Similar results were obtained from at least two independent preparations of each strain of PrPSc.