Oxygen evolution correlation

Influence of catalase activity and electrical conductivity. Parallel to the determination of the oxygen activity. Beck and co-workers 38> investigated the activity for the decomposition of hydrogen peroxide by various chelates. In each case, 1 mg of freshly precipitated pigment was added to 1% hydrogen peroxide solution and the velocity of oxygen evolution was determined volumetri-cally. The results summarized in Table 5 show no correlation between electro-catalytic activity and catalase activity. 

Correlation of the activation energy or overpotential at a given current and for a particular rds on different substrates with relative measures of the heat of chemisorption of intermediates have been successfully made for hydrogen evolution [138], oxygen evolution [139], and oxygen reduction [76], etc. 

In a study of a series of iron-based spinels, Iwakura et al. [313] did not observe a correlation of chlorine evolution overvoltage with the magnetic properties of the oxide. In contrast, a dependence of overpotential on magnetic properties was observed for oxygen evolution. 

Chloride has been recognized as a cofactor required for efficient transfer of electrons from water to P-682, but not for its reduction when artificial electron donors are used [180,181], The exact mechanism of Cl action in O2 evolution still remains unclear. Direct interactions between Mn and Cl ions have been hypothesized by GoPdfel d et al. [182]. Indications in this sense come from the effects of Cl in relation to the inhibition of O2 evolution by NH2OH [181] and by exogenous Mn [183]. Moreover, by utilizing C1 -NMR, a correlation between oxygen evolution... 

The correlation between the rates of the two reactions (corrosion and oxygen evolution) can reveal the effect of Ag in a more clear-cut manner, eliminating the influence of the oxygen over-voltage decrease. Such a relationship is given in Fig. 2.46. 

Another selective inhibitor of the oxygen evolving complex is NH2OH. Treating PS II particles with NH OH (Fig 3) effectively inhibited the oxygen evolution and the water to DCIP reaction. The treatment also resulted in an almost complete (97 %) loss of Mn. The release of Mn correlated well to the inhibition of oxygen evolution and water to DCIP reaction. In contrast, the pseudo catalase activity was only inhibited to some 60 % and was not at all correlated to the release of Mn. Thus, the pseudo catalase activity is not dependent, on either bound or free, Mn. 

The concentration of PSII centres was determined by flash light induced oxygen evolution (7) and correlated with the amount of AP. A Chi to PSII ratio of 120 Chi a/PSII was determined. The molar ratio of PSII to AP was 1 5 Hemi-ellipsoidal phycobilisomes may contain 20-24 moles of AP. Thus the molar ratio of PSII to AP is 4 20 and consequently a tetrameric PSII particle package binds one hemi-ellipsoidal phycobilisome. It is supposed that the aggregation of PSII to dimers and tetra-mers is induced by the phycobilisome structures of the cores. Depending on the type of phycobilisome, different aggregation patterns are realized. 

At low oxygen concentrations has been shown to be correlated with steady state electron flow calculated from gas exchange measurements (1). Here we investigate the validity of this relation during photosynthetic induction in dark adapted spinach leaves. Photosynthetic electron flow was estimated from measurements of the rate of oxygen evolution with the photoacoustic technique (2,3,4). Our results indicate that equation [1] holds during induction, but that Op is very small compared to OpQ, i.e. electron flow is almost completely suppressed in "energized open PS2 reaction centers. 

---