Solid state fluorescence of lyophilized proteins.
Fluorescence spectroscopy has been used to measure changes in the tertiary structure of proteins in the solution state. The sensitivity of fluorescence to the protein tryptophan environment has made it a useful tool for studying protein conformation and stability. Using fluorescence spectroscopy to probe structural alterations in lyophilized proteins has been limited due to technical challenges and overwhelming background light scattering. We have investigated the possibility of analyzing lyophilized proteins using the Cary-Eclipse spectrofluorometer by monitoring the fluorescence of the protein therapeutic after subjecting the lyophilized cake to heat-induced accelerated degradation. We have been able to obtain reproducible fluorescence spectra, detecting possible structural changes under these conditions. Fluorescence and circular dichroism spectroscopic analyses of the reconstituted proteins indicated that changes in fluorescence intensities observed in the solid state could be correlated to that in solution and to possible tertiary structural changes. Size exclusion chromatography analysis of protein Y subject to accelerated degradation showed a correlation between decreasing fluorescence intensity and increasing protein Y tetramer in solution, consistent with long-term stability. This suggests that solid state, intrinsic protein fluorescence measurements using the Cary-Eclipse holder may be feasible for long-term stability studies and formulation development.
Ramachander
Ranjini
R
Product and Process Development, One Amgen Center Drive, Thousand Oaks, CA 91320, USA. ranjinir@amgen.com
Jiang
Yijia
Y
Li
Cynthia
C
Eris
Tamer
T
Young
Meagan
M
Dimitrova
Mariana
M
Narhi
Linda
L
D002850:Chromatography, Gel; D002942:Circular Dichroism; D005453:Fluorescence; D005612:Freeze Drying; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*
D011506:Proteins