Investigation of In Situ Thermal Denaturation of Proteins in Dunning AT-1 Rat Prostate Cancer Cells Using FTIR and DSC

In this study, the in situ protein denaturation in Dunning AT-1 rat prostate cells was studied using FTIR and DSC. The denaturation information from FTIR showed a shift from α helix (amide-I band at 1655cm⁻¹) to β sheet (amide I band at 1620 cm⁻¹). The relative beta sheet area change between 20 °C and 70 °C was used to dynamically scale the thermal denaturation process during heating at 2 °C/min. DSC scans (at scanning rates of 2°C/min and 5°C/min) of the heat flow due to protein denaturation were recorded from 20 °C to 70 °C. The range over which protein denaturation occurs (from 45 °C to 70 °C) was consistent in both studies. By calorimetric experiments with DSC, the enthalpy change during protein denaturation was found to be 27.3±4.0J/g J/g and 25.9±0.5J/g, respectively. In addition, the activation energy and frequency factor were measured by kinetic experiments with both DSC and FTIR. A first order irreversible Arrhenius model was fit to the kinetic data using a flexible tolerance method. The activation energy (E) and frequency factor (A) between 20–70 °C was found to be 107.8kJ/mole and 3.4·10¹⁴ l/s for the FTIR study and 120.9kJ/mole and 3.6·10¹⁶ l/s for DSC analysis at a scanning rate of 2°C/min, respectively. At a scanning rate of 5°C/min, the DSC results gave an activation energy of 144.5kJ/mole and a frequency factor of 4.1·10²⁰ l/s.