Fig. 5.

PSI photoactivity is retained after incorporation into microspheres, and microspheres retain photoactivity after lyophilization. Chelated microspheres containing PSI at a ratio of 500:1. A. Pump-probe spectroscopy was performed to assess PSI electron transfer capability after encapsulation in CaCO₃ microspheres. B. Observed PSI reduction rates (K_obs) are plotted against the concentration of the donor during titration. C. PSI microsphere photoactivity was assessed before and after lyophilization to test long-term stability and compared with WT (free) PSI. Excipients sucrose and trehalose at 5% w/v were also included to assess their effects on lyophilization stability.