Photosynthesis pigment system

We can use the photosynthetic enhancement effect to study the pigments associated with each of the two photochemical systems involved in photosynthesis. The system containing the pigments absorbing beyond 690 nm was... 

Figure 4. The Z-scheme of green plant photosynthesis coupling of the two pigment systems, 1 and II. Peso and p7(Ki = chlorophyll pQ = plastoquiiionc Cyt = cytochrome pC = plastocyaniiie Fdb, Fds = ferredoxin.

Fig. 10. Fluorescence emission and excitation (or absorption) spectra in CSj of p-carotene (A) and fucoxanthin (B). See text for details. Figure source (A) Glllbro and Cogdell (1989) Carotenoid fluorescence. Chem Phys Lett. 158 313. (B) Katoh, Nagashima, and Mimuro (1991) Fluorescence properties of the allenic carotenoid fucoxanthin impiication for energy transfer in photosynthetic pigment systems. Photosynthesis Res 27 223.

Fig. 3. Scheme of photoelectron transport in photosynthesis. The path of photoelectron flow associated with noncyclic photophosphorylation through the two postulated light reactions mediated by Pigment Systems 1 and 2 is indicated by the heavy lines. Redox potentials of electron-carrying cofactors along this path is indicated by scale on the left. Further explanation in text. 

The reduced symmetry of the chromophore, which still contains 187t-electrons and is therefore an aromatic system, influences the electronic spectrum which shows a bathochromic shift and a higher molar extinction coefficient of the long-wavelength absorption bands compared to the porphyrin, so that the photophysical properties of the chlorins resulting from this structural alteration render them naturally suitable as pigments for photosynthesis and also make them of interest in medical applications, e.g. photodynamic tumor therapy (PDT).2... 

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