Pigment-lipid interaction

On the basis of X-ray diffraction studies, the ultrastructure of chloroplast membrane has been analyzed by Kreutz - s, and the subject reviewed by him. Using the freeze-etching technique, Muehlethaler has suggested a picture for the thylakoid membrane based upon the bimolecular leaflet model. The salient feature in all these proposed models lies in their oriented bilayer lipid core, onto which other important cellular constituents, such as proteins and pigments, may interact through either ionic or van der Waals attraction, or both. Muehlethaler s interpretation is of special interest, in view of the experiments using the pigmented... 

Photosystem I is a membrane pigment-protein complex in green plants, algae as well as cyanobacteria, and undergoes redox reactions by using the electrons transferred from photosystem II (PS II) [1], These membrane proteins are considered to be especially interesting in the study of monomolecular assemblies, because their structure contains hydrophilic area that can interact with the subphase as well as hydrophobic domains that can interact either with each other or with detergent and lipids [2], Moreover, studies with such proteins directly at the air-water interface are expected to be a valuable approach for their two-dimensional crystallization. 

A number of lipids are pigments in plants. The most important group is probably carotenoids. The role of carotenoids in plant-insect interactions has been reviewed (81,82). 

Lipid oxidation products react with proteins and other amino compounds to form brown substances, similar to melanoidins. The formation of such brown substances was reviewed already at the first Maillard Symposium.150 The pigments formed are partly soluble in chloroform-methanol and partly insoluble, whereas true melanoidins are largely water-soluble. As most brown pigments of fish muscle are soluble in benzene-methanol and only to a lesser extent in water, the implication is that here oxidised lipid-protein interactions are more important than Maillard browning due to ribose-amino acid interactions. 

Browning due to interaction of oxidised lipids and proteins occurs in vivo, the brown pigment deposited in tissues being termed lipofuscin or ceroid. The appearance of brown discoloration in the adipose tissues of, inter alia, pig, mink, and chicken, has been called the yellow fat disease . Ceroid accumulates slowly and has therefore been described as the age pigment . 

The present paper reviews some of the undesirable effects resulting from the interaction of flavor constituents, lipids and pigments with proteins. Our laboratory as well as others have contributed to this knowledge. 

Research needs include studies about the relationship between antioxidant capacity and carotenoid, chlorophylls and anthocyanins stractures as well as that of their derivatives found in fresh and processed fmits and vegetables. Also the stability and biodisponibility of pigments depending on their nature and interaction with the lipidic enviromnent must be elucidated. 

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