Abstract
The reversible photochemistry of the α-subunit of phycoerythrocyanin (α-PEC) has been measured by low temperature absorption and circular dichroism in the range of 125K to 295 K. Below 185 K, the photochemistry is nearly silent; above 205 K, the photochemistry increases gradually without an indication of intermediates, and between 185 to 205K spectral changes in absorption and circular dichroism indicate an intermediate and/or changes in the interaction(s) between the chromophore and its environment.