Disaccharides are known to protect biological materials against the denaturing effects of drying and freezing. In the present study, we investigate the effect of trehalose on the internal dynamics of a protein with a very sensitive optical spectroscopic method that is able to report conformational transitions separated by barriers as low as about10-6 eV. To focus on such fine steps in protein dynamics, the experiment is performed at cryogenic temperatures. The conformational „motions" in the protein are monitored by the statistical spectral shift of an electronic transition in a marker molecule embedded in the structure. Upon waiting and remeasuring the spectral line, a broadening is observed, because the statistically occurring conformational transformations modify the original electronic transition energy of the population. The phenomenon is called „spectral diffusion". The marker molecules are selected from a population by narrow linewidth laser excition, and the spectral line is detected as a spectral hole in the inhomogeneously broadened absorption origin band. The feature of broadening in time characterizes the internal dynamics of the protein through its perturbing effect on the p electron system of the marker. In our sample, the marker is the prosthetic group of a hemoprotein, Horse Radish Peroxidase, thus the observed dynamics is characteristic for the biological functioning of an enzyme. The spectral diffusion phenomenon is interpreted as a process of anomalous diffusion. The dynamics was studied under three conditions: in 50%glycerol /buffer (V/V), in 40%trehalose /50%glycerol/buffer and in 60%trehalose /25%glycerol/buffer at 4.2 K. We will show that while the architecture of the energy landscape remains the same as in glycerol, the conformational transitions leading to spectral diffusion are faster in 40% trehalose. Further addition of trehalose did not change the kinetics of the process. These results are in agreement with the models that trehalose maintains the internal coordinated water molecules in the structure and thus facilitates the motions of internal dynamics.