David W Randall

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The redox-active tyrosines, Y(Z) and Y(D), of Photosystem II are oxidized by P680+ to the neutral tyrosyl radical. This oxidation thus involves the transfer of the phenolic proton as well as an electron. It has recently been proposed that tyrosine Y(Z) might replace the lost proton by abstraction of a hydrogen atom or a proton from a water molecule bound to(More)
Electron spin echo electron-nuclear double resonance (ESE-ENDOR) experiments performed on a broad radical electron paramagnetic resonance (EPR) signal observed in photosystem II particles depleted of Ca2+ indicate that this signal arises from the redox-active tyrosine YZ. The tyrosine EPR signal width is increased relative to that observed in a(More)
The environment of the photosystem II YZ. radical, trapped in the "split-signal" form, is examined in acetate-treated PSII membranes using pulsed EPR methods. The split-signal line shape is simulated with dipolar and exchange couplings to the Mn cluster of 1260 and -28 MHz, respectively. The 1260-MHz dipolar coupling corresponds to a Mn-YZ. distance of 3.5(More)
centers are summarized and their relation to intra- and inter-protein electron transfer (ET) kinetics are described. Specific contributions of the electronic structures of these two broad classes of Cu ET proteins to H AB, λ, and Δ E° are discussed. Also, the role of the protein structure in determining key geometric features which define the electronic(More)
Detailed electronic and geometric structural descriptions of the blue copper sites in wild-type (WT) stellacyanin and its Q99M and Q99L axial mutants have been obtained using a combination of XAS, resonance Raman, MCD, EPR, and DFT calculations. The results show that the origin of the short Cu-S(Cys) bond in blue copper proteins is the weakened axial(More)
Interparental relationship conflict has consistently been linked to child adjustment problems, with children's perceptions of such conflict particularly predictive of their outcomes. Despite mounting evidence that preschool children can provide reliable and valid accounts of family functioning, little research has examined preschool children's perceptions(More)
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