Artificial systems mimicking

Photophysical processes are commonly encountered and can participate in such important phenomena as energy harvesting (antenna effect), which is the basis for natural photosynthesis and artificial systems mimicking it [4-21] (see below). 

In order to realize an artificial system mimicking photoinduced water oxidation by PSII, three fundamental components (i.e. (i) a photosensitizer, (ii) a catalyst, and (iii) a sacrificial agent) are strictly required. 

Permeability and Associated Assays Orally administered drugs need to cross the intestinal epithelium cell layer to reach the systemic circulation. Therefore, membrane permeability is a major determining factor of intestinal absorption and oral bioavailability for drug molecules. Several in vitro systems mimicking the epithelium cell layer are routinely used in ADME profiling to assess membrane permeability of NCEs. The parallel artificial membrane permeability assay (PAMPA) uses a dual chamber sandwich plate separated by an artificial lipid membrane to simulate the epithelium layer (Figure 6.6A) [75]. Compounds are... 

Stemming from their multifarious roles in natural processes, [metallo] porphyrins have found numerous applications in artificial systems aimed at mimicking important biological functions. Many different metalloporphyrins have been designed in order to accomplish specific tasks and, in particular, novel approaches have been used to assemble several porphyrins into a cluster. This ability to concentrate metalloporphyrins into a supramolecular assembly is of special relevance in that it takes us one step closer to constructing practical devices. This chapter will attempt to review the progress made in the assembly of porphyrin derivatives into supramolecular systems and will describe the aptitude of such assemblies to photosensitize particular reactions. The work described here is primarily concerned with trying to reproduce, under controlled conditions, some of the important features of photosynthetic reaction center complexes. 

There is a possibility that the key processes in photosynthesis involving C, N and S metabolism could be mimicked using the electrons and protons from water splitting. Artificial systems using photochemical and/or photobiological processes might be possible in the future. 

In mimicking this type of function, noncyclic artificial carboxylic ionophores having two terminal groups of hydroxyl and carboxylic acid moieties were synthesized and the selective transport of alkali metal cations were examined by Yamazaki et al. 9 10). Noncyclic polyethers take on a pseudo-cyclic structure when coordinating cations and so it is possible to achieve the desired selectivity for specific cations by adjusting the length of the polyether chain 2). However, they were not able to observe any relationship between the selectivity and the structure of the host molecules in an active transport system using ionophores 1-3 10). (Table 1)... 

From a fundamental viewpoint, carbon dioxide reduction is a model reaction which can help us to understand better the mechanism of natural photosynthesis.11 Development of artificial photosynthetic systems, by mimicking functions of green plants, is one of... 

A biomembrane is an excellent example of supramolecular assemblies, in which various functional molecules are structurally organized for molecular recognition. In order to develop artificial supramolecular systems capable of mimicking biomembrane functions, it seems important to investigate molecular recognition by macrocyclic hosts embedded in synthetic bilayer membranes. 

Several approaches to artificial photosynthesis involve the mimicking of membranes to effect charge separation. An easy extension of the micellar effects described above to systems amenable to study as photosynthetic models can be encountered in the charge separation derived on synthetic vesicles or membranes (275). Sonic dispersal of long chain ammonium halides, phosphates, sulfonate, or carboxylates produces prolate ellipsoidal vesicles with long term stabilities which can entrain and trap molecules in their compartments. With donor-acceptor photosystems, four physical arrangements about the vesicle are important, Fig. 6. 

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