Chemical structure chlorophylls

The chemical structure of dinoflagellate luciferin was found to be a tetrapyrrole, possibly derived from chlorophyll (Nakamura et al., 1989). The luciferase of G. polyedra was cloned (Bae and Hastings, 1994). Recently, the crystal structure of the third domain of the luciferase was determined (Schultz et al., 2005). 

Fig. 8.8 The chemical structures of dinoflagellate luciferin (5), the product of luminescence reaction catalyzed by luciferase (6), air-oxidation product formed at — 20°C (7), and the blue oxidation product (8). Note structural resemblance between these compounds and chlorophylls.

Besides the great pigment classes such as carotenoids, flavonoids, anthocyanins and chlorophylls a wide variety of other pigments have been separated, quantitated and identified by different liquid chromatograpchic techniques. The chemical structures of these pigments show high diversity. Unfortunately, in the majority of cases the biological activity of these... 

Vanadium and nickel are present in parts-per-million quantities in most crude oils, usually in large, oil-soluble organometallic compounds termed porphyrins. The chemical structure of porphyrins is closely akin to the coloring matter in blood and to chlorophyll in plants. 

Figure 5.3 The chemical structure of a chlorophyll and its absorption spectrum...

Because of their basic role in nature, chlorophylls have been the subject of many investigations. For a better understanding of photosynthesis it is necessary that chlorophylls and their derivatives be determined qualitatively and quantitatively. Investigations into their chemical structure, genesis, transformations, and functions in plants supply valuable information for plant physiological studies (92). 

Figure 9.37 Chemical structures of chlorophylls-a and b which contain a propionic acid esterified to a C20 phytol chlorophylls-cj and C2 have an acrylic acid that replaces the propionic acid. Also included are the pheopigments, the four dominant tetrapyrrole derivatives of chloropigments (pheopigments) found in marine and fresh-water/estuarine systems (chlorophyllide, pheophorbide, pheophytin, pyropheophorbide.) More specifically, chlorophyllase-mediated de-esterification reactions (loss of the phytol) of chlorophyll yield chlorophyllides. Pheophytins can be formed when the Mg is lost from the chlorophyll center. Pheophorbides are formed from removal of the Mg from chlorophyllide or removal of the phytol chain from pheophytin, and pyrolyzed pheopigments, such as pyropheophorbide and pyropheophytin, are formed by removal of the methylcarboxylate group (-COOCH3) on the isocylic ring from the C-13 propionic acid group.

Terpenoids, which are also known as isoprenoids, constitute the most abundant and structurally diverse group of plant secondary metabolites, consisting of more than 40,000 different chemical structures. The isoprenoid biosynthetic pathway generates both primary and secondary metabolites that are of great importance to plant growth and survival. Among the primary metabolites produced by this pathway are phytohormones, such as gibberellic acid (GA), abscisic acid (ABA), and cytokinins the carotenoids, such as chlorophylls and plastoquinones involved in photosynthesis the ubiquinones required for respiration and the sterols that influence membrane stmcture (see also Steroid and Triterpene Biosynthesis) (Fig. 1). Monoterpenoids (CIO), sesquiterpenoids (Cl5), diterpenoids (C20), and... 

Thin-layer chromatography (TLC) is mainly applied in micropreparative taxoids separation [2-4]. Silica gel 6OF254 preparative plates are usually applied for this purpose. The problem of taxoids separation involves not only their similar chemical structure (e.g., paclitaxel versus cephalomannine) but also, due to different coextracted compounds usually encountered in crude yew extracts (polar compounds such as phenolics and nonpolar ones such as chlorophylls and biflavones), the separation is very difficult. The common band of paclitaxel and cephalomannine was satisfactorily resolved from an extraneous fraction in isocratic elution with ethyl acetate as a polar modifier [4] and n-heptane-dichloromethane as the solvent mixture and it was of suitable purity for high-performance liquid chromatography (HPLC) quantitative determination. 

All forms of chlorophyll have a similar chemical structure. They have a complex system of rings made of carbon and nitrogen known as a chlorin ring. The five forms of... 

The chemical structure of chlorophyll is very similar to that of hemoglobin, the molecule that transports oxygen in the red blood cells of mammals. The major difference between the two is that hemoglobin contains an atom or iron at the center of a large ring compound, while chlorophyll has an atom of magnesium in the same location. 

Leon Marchlewski (1869-1946), organic chemist, professor of chemistry at Jagiellonian University in Cracow, president (rector) of the University from 1926 to 1928, member of the Polish Academy of Skills and the Warsaw Scientific Society. Discovered similarities in the chemical structure of chlorophyll and haemoglobin in 1912. Author of numerous publications, including the academic textbook Chemia Organiczna (Organic Chemistry). 

Chlorophyll a adsorbed at the oil/water interface catalyzes the electron transport between donors and acceptors of electrons located in the two phases [2,7]. The chemical structure of chlorophyll accounts for its high catalytic activity at the oil/water interface. The asymmetric amphiphilic chlorophyll molecule consists of a hydrophilic head formed by four pyrrole rings located around magnesium and a long tail - the hydrophobic chain of phytol. The hydrophilic head faces the water, while the hydrophobic tail attaches chlorophyll to the non-aqueous phase. 

The basic skeleton of isoprenoids may be modified by the introduction of a wide variety of chemical groups, by isomerization, shift of double bonds, methyl groups, etc. Hence a bewildering number of chemical structures arises. In addition compounds derived from other biogenic pathways may contain isoprene residues. For instance the K vitamins (D 8.1), ubiquinones (D 8.3), chlorophylls (D 10.1), plastoquinones, and tocopherylquinones (D 22.4) have isoprenoid side chains with up to ten isoprene units. Polyketides (D 3.3), alkaloids (D 8.4.2), and coumarins (D 22.2.2) may be substituted by dimethylallyl groups. The terpene residues are attached to nucleophilic sites, such as active methylene groups and phenolic oxygen atoms. 

The structural formula in Fig. 4 indicates the present concept of the chemical structure of chlorophyll-a (the numbering system is that of Hans Fischer). Chlorophyll-b differs from chlorophyll-a with respect to the group at position 3. The methyl group in chlorophyll-a is replaced by an aldehyde group (—CHO) in chlorophyll-b. 

Studies on the chemical structure of chlorophyll showed that it was closely related to heme, a pigment found in mammalian tissue. Subsequent work has indicated that a common biosynthetic pathway exists for the synthesis of porphobilinogen, a precursor to these two pigments. The steps leading to the formation of porphobilinogen were worked out by Shemin and co-workers 0) in a series of brilliant tracer experiments. 

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