Qualitatively, F3, which in addition to histidine also contains trehalose, instead of sucrose, and arginine and polysorbate, behaves similarly to F1 and F2 at terahertz frequencies (Figure ). In solution, excipients, such as arginine, have been shown to inhibit aggregation via interaction with the protein surface . Trehalose is also commonly used to stabilise proteins during lyophilisation and is thought to hinder aggregation via hydrogen bonding between sugar and protein . As evident from the THz-TDS data for F3, the changes in gradient are more defined and the values of T g, = 217 K and T g,↵ = 318 K are lower compared to F1 and F2. This could be due to the stabilising effects of the excipients, as discussed above.