The Role of Terahertz Dynamics in Solid-state Protein Formulations

Utilizing four different model substances, the effect of size on the dynamics of one-component lyophilized (freeze-dried) products was studied with terahertz time-domain spectroscopy and differential scanning calorimetry. While sucrose exhibited the well-known behavior of increasing absorption with temperature observed in small organic molecular systems, the polypeptide bacitracin and the two globular proteins lysozyme and human serum albumin (HSA) showed a more complex temperature dependence. Further analysis was performed on the extrapolated vibrational density of states and the boson peak that showed that localized onset of motions influences the spectrum widely without necessarily leading to an alteration of the rate of absorption change at a single frequency far below room temperature.