In my lecture notes, it states
...there is a significant thermodynamic problem due to the respective redox potentials of the half reactions:
H2O<--> 1/2 O2 + 2H+ +2e- pE=+0.82V
NADP+ +2H+ +2e- <--> NADPH +H+ pE=-0.32V
Could someone please explain what the 'pE' is? I thought it would be just ordinary redox potential, however the redox potential for water is apparently +1.23V not 0.82V. I cannot find anywhere a source stating the figures given above or what they mean (I have also consulted Biochemisty, Stryer et al)
Could it have something to do with this being the potential in the conditions present in a typical chloroplast as opposed to standard conditions?