FTIR study on thermal denaturation and aggregation of recombinant hamster prion protein SHaPrP90-232

We have investigated the temperature induced denaturation and aggregation of the recombinant fragment SHaPrP90-232 of the hamster prion protein by Fourier transform infrared (FTIR) spectroscopy in H2O and D2O buffers. Difference spectra of this denaturation/aggregation reaction revealed a decrease of α-helical and turn structures and an increase of intermolecularly formed antiparallel β-sheet structure. Compared to previously examined critical oligomers in H2O buffer, the temperature induced aggregates of SHaPrP90-232 exhibited a less rigid but still strong hydrogen bonding pattern as indicated by the β-sheet specific difference band at 1624 cm−1. The denaturation/aggregation temperature of SHaPrP90-232 was consistently determined using the β-sheet specific difference band observed in the H2O or in the D2O experiments. Further, the spectra obtained for the critical oligomers produced in appropriate buffer systems at 25 °C and at 37 °C revealed no significant differences in secondary structure.