The obtained tetrapyrrole
solutions were centrifuged (10 min, 16100 xg) and the supernatant was used for HPLC analysis.
In view of the transcendental role played by tetrapyrrole
macrocycles in nature and because of the properties inherent in their synthetic analogues, during the last decade an increased interest has aroused for the synthesis of new materials based on the use of these compounds [4, 33-49].
Our results revealed that tetrapyrrole
and tetraphenyl rings in [TPPS.sub.4] maintain a co-planar structure to fulfill the p-[pi] electron conjugation over the rings, and such configuration may further stabilize the entire molecule.
The aromaticity of the linear tetrapyrrole
bilirubin structure confers broad absorptivity in the ultraviolet and visible spectra, but this product of heme metabolism also is a highly reactive chemical species, a property that may contribute to its toxicity in biological systems.
Specific topics include conducting polymer nanocomposite membranes, the role of tetrapyrrole
pigment-oriented thin films in the detection of volatile organic compounds, electronic noses and tongues, and applications of sensors in food and environmental analysis.
NO has been reported to inhibit methionine synthase activity in vitro [6-8], it might be expected to bind to the cobalt in cobalamin because (i) NO binds tightly to the iron in heme; (ii) ferrous heme and cbl (III) are isoelectronic; and (iii) in both heme and cobalamin, the metal ion is coordinated to four in-plane nitrogen atoms of a tetrapyrrole
ring and has two out-of-plane ligands .
NO has been reported to inhibit methionine synthase activity in vitro (37-39), and it might be expected to bind to the cobalt in cobalamin because, first, NO binds tightly to the iron in heme (40); second, ferrous heme and cbl(III) are isoelectronic; and third, in both heme and cobalamin, the metal ion is coordinated to four in-plane nitrogen atoms of a tetrapyrrole
ring and has two out-of-plane ligands (41).
This protein contains a tetrapyrrole
phycocyanobilin, which is responsible for antioxidant properties of Pc .
Other topics include leaf senescence, the biology of arabinogalactan proteins, light regulation of stomatal movement, tetrapyrrole
biosynthesis in higher plants, ATP-binding cassette transporters, and tracheary element differentiation.
One of the major metabolites of spirulina is the fluorescent, deep blue coloured protein namely c-phycocyanin (c-pc) which consists of an open chain tetrapyrrole
chromophore-phycocyanobillin, and a covalently linked apoprotein (Grossman et al., 1993).
PBGD, which is the third enzyme in heme biosynthesis, catalyzes the polymerization of porphobilinogen (PBG), yielding a linear tetrapyrrole
, preuroporphyrinogen (hydroxymethylbilane).
Vitamin [B.sub.12] is usually used as a generic term representing various cobalt-containing tetrapyrrole
rings with attached nucleotide side chains that are chemically classified as cobalamins or corrinoids.