Cluster backbone

For an estimation of the concentration-dependence of the elastic modulus G it is necessary to consider the elastic modulus GA of the CCA-clusters more closely. By referring to the analytical results, Eqs. (56)—(59) of Kantor and Web-man [91],one obtains the elastic modulus of the elastically effective CCA-cluster backbone as the bending-twisting modulus of tender, curved rods [60,63,64] ... 

Fig. 1.2. Portion of a random bond percolating cluster backbone, connecting the points A and B. Here, the thick black lines represent the singly connected bonds or red bonds which, if cut, will disconnect the connection between A and B. The bonds in the blob portions are indicated by dotted lines. The dangling bonds are indicated by thin black lines (cf. StauflPer and Aharony 1992).

Fig. 7. Comparison of the cluster binding fold of the water-soluble Rieske fragment from bovine heart 6ci complex (ISF, left PDB file IRIE) with the structure of ru-bredoxin (middle PDB file 7RXN) and with the zinc-ribbon motif (right PDB file ITFl). The metal binding loops are shown as ball-and-stick models of the backbone atoms.

Fig. 2. Protein backbone representations of (a) the 2[4Fe-4S] ferredoxin from Peptococcus aerogenes, (b) the proposed structure of the FA/FB-binding protein of PSl based on the 4 A crystsd structure (25), and (c) the [3Fe-4S][4Fe-4S] ferredoxin from Sulfolo-bus acidocaldarius. Ligands to clusters Fa and Fb, important residues as well as the loop extension (see text) EU e highlighted in darker gray.

Both the 3i4- and 2.5i2-helical backbones have been found suitable for the design of antimicrobial /9-peptides. In order to cluster polar residues on one face of the helix, amphiphilic 3i4-helical /9-peptides have been constructed from hydro-phobic-cationic-hydrophobic or hydrophobic-hydrophobic-cationic residue triads... 

Density functional theory (D FT) modeling calculations show that a dinuclear gold(I) amidinate complex is less stable than the tetranuclear gold(I) amidinate cluster, [Au4(HNC(H)NH)4]. However, replacing C by Si in the backbone reduces ring strain and makes the energies similar. Figures 1.21 and 1.22 [39]. 

As long as the spacer molecules are not covalently bound to the cluster surface and the spacer molecules have no delocalized rc-electron system along their backbone between their termini, this relation is valid. The respective activation energy drops as soon as covalently linking species, equipped with delocalized n electrons... 

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