TY - JOUR
T1 - EPR kinetic studies of the S-1 state in spinach thylakoids
AU - Razeghifard, M. Reza
AU - Kuzek, Damien
AU - Pace, Ron J.
PY - 2005/6/1
Y1 - 2005/6/1
N2 - The YZ• decay kinetics in a formal S -1 state, regarded as a reduced state of the oxygen evolving complex, was determined using time-resolved EPR spectroscopy. This S-1 state was generated by biochemical treatment of thylakoid membranes with hydrazine. The steady-state oxygen evolution of the sample was used to optimize the biochemical procedure for performing EPR experiments. A high yield of the S -1 state was generated as judged by the two-flash delay in the first maximum of oxygen evolution in Joliot flash-type experiments. We have shown that the YZ• re-reduction rate by the S-1 state is much slower than that of any other S-state transition in hydrazine-treated samples. This slow reduction rate in the S-1 to S0 transition, which is in the order of the S3 to S 0 transition rate, suggests that this transition is accompanied by some structural rearrangements. Possible explanations of this unique, slow reduction rate in the S-1 to S0 transition are considered, in light of earlier observations by others on hydrazine/hydroxylamine reduced PS II samples.
AB - The YZ• decay kinetics in a formal S -1 state, regarded as a reduced state of the oxygen evolving complex, was determined using time-resolved EPR spectroscopy. This S-1 state was generated by biochemical treatment of thylakoid membranes with hydrazine. The steady-state oxygen evolution of the sample was used to optimize the biochemical procedure for performing EPR experiments. A high yield of the S -1 state was generated as judged by the two-flash delay in the first maximum of oxygen evolution in Joliot flash-type experiments. We have shown that the YZ• re-reduction rate by the S-1 state is much slower than that of any other S-state transition in hydrazine-treated samples. This slow reduction rate in the S-1 to S0 transition, which is in the order of the S3 to S 0 transition rate, suggests that this transition is accompanied by some structural rearrangements. Possible explanations of this unique, slow reduction rate in the S-1 to S0 transition are considered, in light of earlier observations by others on hydrazine/hydroxylamine reduced PS II samples.
KW - Hydrazine
KW - Oxygen evolving complex
KW - Photosystem II
KW - Super-reduced state
KW - Tyrosine Z reduction kinetics
UR - http://www.scopus.com/inward/record.url?scp=20444422867&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2005.03.010
DO - 10.1016/j.bbabio.2005.03.010
M3 - Article
SN - 0005-2728
VL - 1708
SP - 35
EP - 41
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 1
ER -