Carotenoids in biological membranes
Chemical structure of carotenoids:
The simplest carotenoid (C40H56, lycopene) is built of eight isoprenoid units forming a long central chain of conjugated double bonds. Others carotenoids are derivatives of this acyclic structure by hydrogenation, dehydrogenation, cyclization, oxidation. Carotenoids are divided into two groups. The first one (carotenes) constitutes those containing only carbon and hydrogen atom. The other group constitutes oxygenated derivatives of carotenes, and is known as xanthophylls.
Occurrence in nature:
Carotenoids are pigments that are widely spread in nature. They are present in all photosynthetic organisms (plants, algae, bacteria), in most non-photosynthetic bacteria, some yeasts and molds and in some animals tissue such as retina
Function of carotenoids in living organisms:
Carotenoids play numerous functions in living organisms. They act as accessory pigments in photosynthesis, are antioxidants, protect against damage caused by light and oxygen. They are responsible for coloration of plant leaves, fruits and flowers, as well as for colors of some birds, insects, fish, and crustaceans.
Localization and action of carotenoids in lipid membrane:
The majority of carotenoids, which can be found in living organisms, are located in biological membranes. Most of them are functionally connected with membranes proteins. Rests occur directly in lipid part of membrane. Such localization let carotenoids influence structural and dynamical properties of membrane, and following that, their biological function. Carotenoids interact with lipids hydrocarbon chains by van der Waals interactions. This influence trans-gauche isomeryzation of alkyl chains, but also lateral and rotational diffusion of all lipids molecules. There is hypothesis saying that carotenoids, as well as cholesterol decrease fluidity of biological membranes. Experimental data confirm such hypothesis.
Goal of investigation
Determinate the effect of β-carotene on a phosphatidylcholine bilayer built of PCs with one saturated and one mono-unsaturated acyl chain (1-palmitoylo-2-oleyl-phosphatidylcholone POPC).
Determinate the effect of macular carotenoids (zeaxanthin, meso-zeazantin, lutein ) on retinal membrane.