Clusters experimentally isolated

The ferredoxins isolated from D. gigas have been quite extensively studied by different experimental approaches and spectroscopic techniques and will be used here as a reference system. Ferredoxin I D. gigas Fdl) and ferredoxin II (D. gigas Fdll) (60-62) are composed of the same polypeptide chain (58 amino acids, 6 cysteines) (63). D. gigas Fdl is a dimer and contains a single [4Fe-4S], whereas the same monomeric unit of the tetrameric D. gigas Fdll contains a single [3Fe-4S] ° cluster. 

Although this estimate of the interaction energy between defects is simplistic, it demonstrates that a fair number of defects may cluster together rather than remain as isolated point defects, provided, of course, that they can diffuse through the crystal. It is difficult, experimentally, to determine the absolute numbers of point defects present in a crystal, and doubly so to determine the percentage that might be associated rather than separate. It is in both of these areas that theoretical calculations are able to bear fruit. 

In the light of several allotropic modifications known for phosphorus, the relatively high single bond energies and the tendency of phosphorus to catenate it remains mysterious, and that apart from P4 and As4 only very scarce information on isolated E cluster molecules is available from hard experimental data. In contrast, a vast amount of solid theoretical work has been performed [11],... 

Notes on cluster phases in triel alloys. Li and Corbett (2004) have shortly reviewed the systematic and extensive experimental and theoretical work carried out by Corbett and co-workers (see for instance Corbett 1996). Considering alkali metal-triel alloys, they underlined, particularly for Ga, In and Tl, the richness of their chemistry (see also 5.3.4.4). Gallium forms many anionic network structures (and only a few phases containing isolated cluster units), indium gives several examples of both network and discrete cluster structures, thallium forms especially discrete clusters (Tl , T157A Tl , Tl , Tl(f, Tl ). 

Atomic and molecular clusters have been studied for more than fifty years, but the last two decades have seen an increasing interest in new experimental methods for cluster production and analysis. The development and improvement of cluster sources lie at the focal point of the technological advances achieved in the study of gas phase clusters. For what concern the molecules of biological interest, the production and analysis of these molecules both isolated or complexed is made... 

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