Abstract
The molecular mobility of lyophilized formulations containing various polymer excipients was determined by solid state pulsed ^1H-NMR and high resolution ^<13>C-NMR, and discussed in relation to protein stability in the formulations. The critical mobility temperature, T_<mc> of these formulations, at which a Lorentzian relaxation process due to liquid-like polymer protons appeared, varied among the polymer excipients, and increased with decreasing water content and increasing polymer molecular weight. The correlation time, τc, of carbonyl carbon of bovine serum γ-globulin in formulations containing dextran decreased substantially at temperatures above T_<mc> in a similar way as the τc of dextran methin carbon. This suggests that the molecular mobility of protein is enhanced at temperatures above T_<mc> by the increased mobility of dextran molecules. Protein aggregation during the storage of these formulations increased substantially at temperatures above T_<mc>, indicating that storage stability of lyophilized protein formulations is closelv related to their molecular mobility.
