... binding of aDCMU molecule in the QBpocket; the remaining PSIIcenters are unaffected. However, a saturating concen-tration of DCMU would inhibit completely the activity of PSII by preventing ... FEBS 4773 of QA– in PSII centers that are affected by the nonsatu-rating concentration of inhibitor [7,8]. The Em of QAisraised in the presence of DCMU in the QBpocket,making it energetically ... N,N,N¢,N¢-tetramethyl-p-phenylenediamine [23,24].The use of a nonsaturating concentration of DCMU,an inhibitor known to close the PSII reaction center by binding in the QBpocket and blocking electron transferfrom...