
%0 Journal Article
%A YAMASHITA, Takashi 
%T Reversible heat-inactivation and photo-reactivation of oxygen evolving center (OEC) of 
spinach chloroplasts
%J Science Access
%D 2001/01/01
%V 3
%N 1
%P -
%K 
%R https://doi.org/10.1071/SA0403337
%U https://www.publish.csiro.au/paper/SA0403337 
%X OEC of chloroplasts is very sensitive to irreversible heat-inactivation when heated at 50oC for 5 min. However, this study introduced a new method for the reversible heat-inactivation and the recovery of OEC activity by photo-reactivation. For the reversible heat-inactivation chloroplasts must be heated in the presence of reduced DCPIP (0.05-0.1 mM) by small amount (0.5 ml) in a tiny test tube in very short time (30 sec) by shaking very vigorously in a water bath at 50oC in the dark. By this heating the chloroplast OEC activity decreased to 15% but the 70% activity could be recovered by applying the photo-reactivation, that is the incubation of chloroplasts with Mn2+, Ca2+ and a reductant for 20 min under illumination of 300 lux white light at 20oC, the same conditions used for the reactivation of Tris-inactivated chloroplasts. The evidence of inactivation and reactivation in OEC or PSII reaction center was demonstrated by the observation of depression and restoration of actinic light-induced chlorophyll fluorescence rise. By photo-reactivation a part of low-potential form Cyt-b559 of heat-inactivated chloroplasts was brought back to the high-potential form 
