Jd. Brewster et al., STORAGE AND IMMOBILIZATION OF PHOTOSYSTEM-II REACTION CENTERS USED INAN ASSAY FOR HERBICIDES, Analytical chemistry, 67(7), 1995, pp. 1296-1299
Significant improvements in a previously described method for detectio
n of herbicides at nanogram per milliliter concentrations are describe
d. The activity of photosystem II reaction centers from spinach thylak
oids was extended from hours to over 6 months by rapid freezing and st
orage at -70 degrees C in appropriate cryoprotection media. Freeze-dri
ed reaction centers were also stable for at least 3 months at 4 degree
s C. Reaction centers immobilized in calcium alginate gels retained ac
tivity for 1 week at 4 degrees C, and immobilization permitted optical
and chemical interference by milli samples to be eliminated.