Photosynthetic pigment Chlorophylls

Such a process can naturally be expected to play a certain part in the mechanism of directed energy transport in biological systems, in particular, in the transfer of absorbed energy from the antenna chlorophyll molecules to the reactive center in the photosynthetic system of plants. In Ref. [30], energy exchange between molecules of the photosynthetic pigments chlorophyll a and pheophytin a was studied experimentally with pigments introduced into the polar matrix. 

Figure 6.6 Two photosynthetic pigments chlorophyll (npper diagram), and the hR retinyhdene chro-mophore, which consists of a carotenoid, retinal, hnked to a Schiff-base, itself linked to a lysozyme residue of bR (29-31). Retinal is in its all-trans conformation in the intermediate diagram, and in its 13-cw conformation in the lower diagram. Conventional atom numbering of retinal is shown.

Photosynthetic pigments, chlorophylls, and carotenoids have a clear hydro-phobic character and are usually analyzed by C18-reversed-phase (RP) columns. A C30-RP appeared on the market. The C30-RP is particularly efficient in the separation of carotenoids because the interactions of the pigments and the stationary phase are maximized by the similar size. With this phase, many cis isomers of the same carotenoid are separated from each other (Emenhiser et al., 1995 Lacker et al., 1999 Sharpless et al., 1996). This C30-RP has been successfully applied to the determination of saponified carotenoids in orange juice (Rousseff et al., 1996). However, when a mixture is complex, coelutions may become rapidly limiting and less selective stationary phases, such as the C18-RP, are therefore preferably... 

The main focus of our work is photosynthetic pigments (chlorophylls, bacteriochlorophylls, and carotenoids). The important absorptions cover the spectral range from 300 to around 850 nm. Single HPLC runs last typically 30 min and use gradient elution, and 10-15 compounds are not uncommon. No dedicated machine was available at the time when the system was installed we therefore use a general purpose spectrometer with a semimicro flow cell (30 fil) and without beam focusing. Since the... 

The photosynthetic pigment chlorophyll mediates the primary act of photosynthesis in higher plants. However, chlorophyll can also catalyze electron transfer reactions at oil/water interfaces and on bilayer lipid membranes without illumination [2, 7, 38]. The reversible chemical reduction of chlorophyll by zinc was first studied by Timiriazeff [44], and the role of chlorophyll in oxidation-reduction reactions has been the subject of numerous later investigations [45],... 

Key words Photosynthetic pigments -chlorophyll a - Langmuir-Blodgett films... 

The isoprenoid hycrocarbons pristane and phytane (derived from the phytol side chain of chlorophyll), as well as porphyrins, have been detected in organic extracts of the Nonesuch Shale of 1.1 billion year age [23]. Their presence points to the existence of photosynthetic pigments in the Precambrian era, but it is also possible that these extractable substances could have been contributed to the rock at a later time. However, in this instance contamination appears to be less likely on account of the large abundance of organic material in this shale. 

Chlorophylls are also composed of four pyrroles, but these are arranged in a ring, called a porphyrin (Figure 22.25c). The chlorophylls are green photosynthetic pigments foimd in plants and some bacteria (Figure 22.25d). Another important class of... 

---