PT  - JOURNAL ARTICLE
AU  - Townsend, Michael W.
AU  - Patrick P. Deluca, Marlys E.
TI  - Use of Lyoprotectants in the Freeze-Drying of a Model Protein, Ribonuclease A
DP  - 1988 Nov 01
TA  - PDA Journal of Pharmaceutical Science and Technology
PG  - 190--199
VI  - 42
IP  - 6
4099  - http://journal.pda.org/content/42/6/190.short
4100  - http://journal.pda.org/content/42/6/190.full
SO  - PDA J Pharm Sci Technol1988 Nov 01; 42
AB  - Purified ribonuclease A (RNase), when freeze-dried in 0.1 M sodium phosphate buffer at pH 3.0, 6.4, and 10.0 was found to lose specific activity as a function of time when stored in the solid state at 45°C. The specific activity loss was a result of the formation of covalently bonded aggregates of RNase. The covalent linkages in the aggregates were not due to disulfide bond interchange. Sucrose, Ficoll 70, and polyvinylpyrrolidone offered lyoprotection by preserving the enzymatic activity of the freeze-dried RNase. (Lyoprotection was defined as the stabilization and prevention of the degradation of a macromolecule both during freeze-drying and afterwards, during storage.) Ficoll 70, a polymer containing sucrose residues, demonstrated the widest range of pH stability and conveyed equivalent lyoprotection at the three pH values tested (3.0,6.4, and 10.0). Sucrose was found to be an effective lyoprotectant only at neutral and alkaline pH, and polyvinylpyrrolidone (PVP) was most effective as a lyoprotectant in an acidic environment. Freeze-dried cakes containing RNase and one of the three lyoprotectants were found to be amorphous and not crystalline solids. Lyoprotectant to RNase mass ratios of at least 6:1 were required to achieve maximum preservation of RNase enzymatic activity for both polymers and sucrose at their respective optimal pH conditions.