Apparent discrepancies with membrane

Photophysical studies allow the measurement of rate constants for transmembrane electron transfer. The distributed kinetics observed in describing the decay of photovoltage across a BLM is consistent with a highly inhomogeneous disposition of donors and relays within the membrane [111, 112]. A typical value for the rate constant for electron transfer across a BLM (about 10 sec-1) would predict a spatial separation of about 10 A, whereas the thickness of the bilayer is usually about 40-50 A. This apparent discrepancy can be resolved if transmembrane electron transfer occurs by several sequential steps involving deeply buried redox sites, thus decreasing the operational tunnelling distance [113]. 

Oxidation of very-long-chain fatty acids is predominantly if not exclusively peroxisomal, although C26 0-CoA can be oxidized by the mitochondrial P-oxidation system provided the mitochondrial membrane is disrupted. The most likely explanation for this apparent discrepancy is that carnitine palmitoyltransferase I (CPTI) is not reactive with C26 0-CoA so that C26 0 simply can not enter the mitochondrial ace. 

These apparent discrepancies (from no degradation to measurable and significant performance loss with each cycle) in the various literature results can perhaps be attributed to differences in the experimental protocol and in the details of the cell assembly. In particnlar, one expects that differences in membrane electrode assembly (MEA) fabrication technique can have considerable impact on the location of where water collects in the cold state, and on the relative strength of adhesion between adjacent layers. 

The reaction center is built up from four polypeptide chains, three of which are called L, M, and H because they were thought to have light, medium, and heavy molecular masses as deduced from their electrophoretic mobility on SDS-PAGE. Subsequent amino acid sequence determinations showed, however, that the H chain is in fact the smallest with 258 amino acids, followed by the L chain with 273 amino acids. The M chain is the largest polypeptide with 323 amino acids. This discrepancy between apparent relative masses and real molecular weights illustrates the uncertainty in deducing molecular masses of membrane-bound proteins from their mobility in electrophoretic gels. 

Although as a class the chelates are definitely bacteriostatic, the relative contributions of uptake and dissociation for both inert and labile species need to be more clearly defined before a full picture is obtained. The results suggest that kinetic reactivity may be more important than thermodynamic stability [30]. In the case of copper(II) complexes with 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthrolines, more recent studies showed that the major mode of action on P. denitrificans in vitro was in fact inhibition of respiratory electron transport in the cytoplasmic membrane, no correlation with inhibition of macromolecular synthesis being apparent [31]. These results are relevant in view of the discrepancy in the reported antitumour activity of these species (see Section 6.2). 

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