pH and temperature dependence of tyrosine Z decay kinetics in Tris-treated PSII particles [prepared from spinach [Spinacia oleracea]] studies by time-resolved EPR
1997
Shigemori, K. (Kwansei Gakuin Univ., Nishinomiya, Hyogo (Japan)) | Mino, H. | Kawamori, A.
The decay kinetics of tyrosine Z (Yz) in Tris-treated Photosystem II particles were measured by time-resolved EPR at different pH values (pH 5.5 to 7.5) between 230 and 297 K. Yz induced by laser flashes decayed in a biphasic way; t(1/2) values were about 100 ms in the fast phase and about 1 s in the slow one, respectively, at room temperature. The fast phase was attributed to a recombination of charges on Yz and Qa. The activation energies for the reaction of Yz with Qa between 245 and 297 K have been estimated to be more than 38 kJ mol(-1) at pH (6.5) and less than 32 kJ mol(-1) at pH (6.5), respectively. The activation energy gap between high pH (6.5) and low pH (6.0) ranges was found to be deltaE
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