Rh. Schweitzer et Gw. Brudvig, SYNTHESIS AND CHARACTERIZATION OF AN INTERNAL EMISSION STANDARD AND APPLICATIONS TO FLUORESCENCE STUDIES OF PHOTOSYSTEM-II, Biospectroscopy, 2(3), 1996, pp. 167-171
Fluorescence measurements of photosynthetic organisms and isolated pro
teins at ambient and low temperature have played an important role in
understanding their function. When comparing fluorescence measurements
at cryogenic temperatures, the differences in the scattering properti
es of frozen samples make it difficult to compare the fluorescence int
ensity of these samples. An internal emission standard can be used to
scale the fluorescence intensity, compensating for these differences.
We report the synthesis, purification and characterization of a lumine
scent terbium chelate complex for use as an internal emission standard
for the study of photosystem II fluorescence at cryogenic temperature
s. The ligand consists of a diethylenetriaminepentaacetic acid derivat
ive where pyrimidine rings sensitize the terbium luminescence, overcom
ing the inherently low absorption of terbium. The chelated lanthanide
remains in solution in the aqueous phase and does not interfere with p
hotosystem II function. By scaling to the terbium emission, the fluore
scence intensity of different samples can be readily compared. This ch
elate complex could also be used as an internal emission standard for
studies of other proteins. (C) 1996 John Wiley & Sons, Inc.