Aggregates pigments

We see from the dependence of the CD spectra in amide UV region on the TPP/PP molar ratio that the mainly nonregular conformation of free peptide is gradually converted into more regular (X-helical structure in complexes (Fig.l.a). Simultaneously, in the time resolved fluorescence experiment the nonexponential fluorescence decay observed for the free (aggregated) pigment is replaced by the two exponential decay kinetics with components of 24D ps and 2.4 ns. The contribution ot the... 

The second process to finish phthalocyanine, which is more important for P-copper phthalocyanine, involves grinding the dry or aqueous form in a ball mill or a kneader (64). Agents such as sodium chloride, which have to be removed by boiling with water after the grinding, are used. Solvents like aromatic hydrocarbons, xylene, nitrobenzene or chlorobenzene, alcohols, ketones, or esters can be used (1). In the absence of a solvent, the cmde P-phthalocyanine is converted to the a-form (57,65) and has to be treated with a solvent to regain the P-modification. The aggregate stmcture also has an impact on the dispersion behavior of a- and P-copper phthalocyanine pigments (66). 

Pigment aggregates are separated into individual particles by a variety of dispersion equipment (77,78), which transmit shear stress of sufficient magnitude to break up the aggregates. If tittle force is required, low viscosity dispersions can be made using equipment that provides low shear stresses. 

Specific carotenoid-protein complexes have been reported in plants and invertebrates (cyanobacteria, crustaceans, silkworms, etc.), while data on the existence of carotenoproteins in vertebrates are more limited. As alternatives for their water solubilization, carotenoids could use small cytosolic carrier vesicles." Carotenoids can also be present in very fine physical dispersions (or crystalline aggregates) in aqueous media of oranges, tomatoes, and carrots. Thus these physicochemical characteristics of carotenoids as well as those of other pigments are important issues for the understanding of their bioavailability. 

The phycobiliproteins are accessory photosynthetic pigments aggregated in cells as phycobilisomes that are attached to the thylakoid membrane of the chloroplast. The red phycobiliproteins (phycoerythrin) and the blue phycobiliprotein (phycocy-anin) are soluble in water and can serve as natural colorants in foods, cosmetics, and pharmaceuticals. Chemically, the phycobiliproteins are built from chro-mophores — bilins — that are open-chain tetrapyrroles covalently linked via thio-ether bonds to an apoprotein. ... 

In any discussion of the dispersion phase, the physical state of the aggregates, whether they are inorganic pigments or organic medicaments, must be considered. The following physical states may occur ... 

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