Is the Protein Dynamical Transition Useful?*

Terahertz Time Domain spectroscopy (THz TDS) has been used to characterize the protein dynamical transition [1, 2] .Typically the THz measurements are performed using solutions, however there is some question as to whether the freezing of the solution effects protein structure or dynamics. To address these questions we performed terahertz dynamical transition measurements in the 100-270 K range and between 0.15 – 2.00 THz on buffered solutions, dry glycerol solutions and minimally hydrated glyercol solutions. Buffer solution measurements using chicken egg white lysozyme and myoglobin protein with concentrations between 2 – 30 mM follow Beer’s law concentration dependence below 15 mM from which terahertz molar absorptivity of the hydrated protein can be extracted. For dry glycerol-protein solutions, the dynamical transition is absent, although it is present for 0.5 g water/g protein indicating that freezing of bulk water does not effect the measurements.
1. He, Y.F., et al., Phys. Rev. Lett., 2008. DOI: 10.1103/PhysRevLett.101.178103.
2. Markelz, A.G., et al., Chem. Phys. Lett., 2007. DOI: 10.1016/j.cplett.2007.05,080.