Secondary structure and aggregation behavior of proteins, as determined in situ in Typha latifolia pollen, were studied by means of Fourier transform infrared microspectroscopy. The amide-I band, arising from the peptide backbone, was recorded over a temperature range from -50 to 120°C at different hydration levels of the pollen. Dehydration increased the denaturation temperature of the proteins and decreased the extent of protein structural rearrangements due to heating. Below 0.16 g H2O/g dry weight (DW), the temperature at which the proteins began to denature increased rapidly. In fully hydrated pollen, denaturation commenced above 60°C, whereas in very dry pollen (0.01 g H2O/g DW) it did at approximately 116°C. Temperature-induced aggregation of proteins was accompanied by the appearance of an infrared band in the region between 1625 and 1630 cm-1 and a weak band around 1692 cm-1. These bands are characteristic of intermolecular extended β-sheet structures. The α-helical band position (band around 1657 cm-1) did not shift substantially over a temperature range from -40 to 120°C at all the water contents tested, indicating that α-helical structures are particularly heat stable. We show here that the proteins in dry desiccation-tolerant pollen are particularly heat stable.
Wolkers, W. F., & Hoekstra, F. A. (1997). Heat stability of proteins in desiccation tolerant cattail pollen (Typha latifolia): A Fourier transform infrared spectroscopic study. Comparative Biochemistry and Physiology, 3, 349-355. https://doi.org/10.1016/S0300-9629(96)00274-5