  The 200 K protein dynamical transition is observed for the first time in the
teraherz dielectric response. The complex dielectric permittivity $\epsilon$ =
$\epsilon$' + i$\epsilon$" is determined in the 0.2 - 2.0 THz and 80-294 K
ranges. $\epsilon$" has a linear temperature dependence up to 200 K then
sharply increases. The low temperature linear dependence in $\epsilon$"
indicates anharmonicity for temperatures 80 K < T < 180 K, challenging the
assumed harmonicity below 200K. The temperature dependence is consistent with
beta relaxation response and shows the protein motions involved in the
dynamical transition extend to subpicosecond time scales.
