Pigments from model systems

Until a recent x-ray diffraction study (17) provided direct evidence of the arrangement of the pigment species in the reaction center of the photosynthetic bacterium Rhodopseudomonas Viridis, a considerable amount of all evidence pertaining to the internal molecular architecture of plant or bacterial reaction centers was inferred from the results of in vitro spectroscopic experiments and from work on model systems (5, 18, 19). Aside from their use as indirect probes of the structure and function of plant and bacterial reaction centers, model studies have also provided insights into the development of potential biomimetic solar energy conversion systems. In this regard, the work of Netzel and co-workers (20-22) is particularly noteworthy, and in addition, is quite relevant to the material discussed at this conference. 

In coating technology, surfaces are coated to protect them from corrosion. This is usually done by a layer containing polymer, pigment, etc.. As a model system, thin polystyrene films on silicon oxide have been studied [150,151]. Does polystyrene form a stable layer or would you expect it to dewet the surfaces assuming that van der Waals forces dominate ... 

A. V. Clark and S. R. Tannenbaum, Isolation and characterization of pigments from protein-carbonyl systems. Models for two insulin-glucose pigments, J. Agric. Food Chem., 1974, 22, 1089-1093. 

Moller, J.K.S., Jensen, J.S., and Skibsted LH. (2003). Microbial formation of nitrite-cured pigment, nitrosylmyoglobin, from metmyoglobin in model systems and smoked fermented sausages by Lactobacillus fermentum strains and a commercial starter culture. Eur. Food Res. Tech. 216, 6,463 69. 

The probable involvement of xanthylium salts in red wine color change is supported by the fact that their absorption maxima match well with the increase in yellow color around 420 nm observed during ageing of red wine. Thus, Liao et al. (22) demonstrated in model systems that reactions between anthocyanins and flavan-3-ols give rise to orange-yellow (440 nm) pigmented products. Based on the earlier observations of Jurd Somers (24) and Hrazdina Borzell (48 such products have been postulated to be xanthylium salts proceeding from direct anthocyanin-flavanol adducts. 

Isomerically pure biliverdin can be prepared from pure bilirubin IXa by oxidation with chloranil acidic reagents cause some isomerization with formation of the III and XllI isomers. A variety of synthetic and spectroscopic studies have been carried out by the Vienna group on model systems" related to the reduced bile pigments, in connection with studies of the conformation and... 

The close relationship of Bulgaria and Daldinia with Hypoxylon in the Xylariaceae is illustrated by the occurrence in some Hypoxylon species of perylenequinones and their relatives (Table 22). The structure of hypoxylone (269), the main pigment of the dark purple carpophores of Hypoxylon sclerophaeum collected in French Guyana, followed from analysis of the and C-n.m.r. spectra and comparison with model systems 107). The naphthyl-naphthoquinone structure of hypoxylone suggests oxidative coupling between naphthalene-1,8-diol (258) and naphthalene-1,4,5-triol. 

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