Degree of labeling (DoL) for the 3 modified PSI used in this study. The values were determined by UV/vis spectroscopy in buffer D and are stated as dyes per PSI trimer (n.a. – not applicable).

Construct	DoL (ATTO 590)	DoL (ATTO 532)
PSI-ATTO590	11	n.a.
PSI-ATTO532	n.a.	12
PSI-ATTO-mix	8	11