Membrane, artificial excitability

Carotenoids are highly lipophilic an active area of research concerns how carotenoids interact with and affect membrane systems (see Chapters 2 and 10). Also, the lipid solubility of these compounds has important implications for carotenoid intestinal absorption (see Chapter 17) models such as the Caco-2 cell model are being used to conduct detailed studies of carotenoid absorption/ competition for absorption (Chapter 18). The lipid solubility of these carotenoids also leads to the aggregation of carotenoids (see Chapter 3). Carotenoids aggregate both in natural and artificial systems, with implications for carotenoid excited states (see Chapter 8). This has implications for a new indication for carotenoids, namely, serving as potential materials for harnessing solar energy. 

Perhaps most exciting is that we are now living in a time when enough knowledge has accumulated so that there are initial attempts to fabricate versions of living cells in the laboratory. Entire genomes have been transferred from one bacterial species to another, and it is now possible to reconstitute a system of membranes, DNA, RNA and ribosomes that can synthesize a specific protein in an artificial cell. 

Explosive research activity is going on in micellar photochemistry. This is related to the development of artificial photosynthetic systems, and the anisotropic nature of globular micelles and bilayer membranes is used for conservation of excitation energy. The subject has been recently reviewed (Kalyanasundaram, 1978). 

Of course, nowadays it is still impossible to utilize in the artificial membrane systems the primary electron excitation with the same efficiency as in natural ones. One of the reasons for this is the lack of sufficient knowledge about the fate of the electron excitation in these systems. The quantitative data about the dissipation of the electron excitation in such systems are quite scares. In the present section we shall discuss these data. 

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