Dimer structures

The 778 present lithium organic structures in the CSD contain 3228 Li—C contacts. This means that every lithium atom either forms a multiple contact to the related carbanion or that most of the structures dimerize around the metal or both. On average, every lithium shows four Li—C contacts and certainly it is not just coincidence that this number is identical to the favorite coordination number of lithium in a molecular environment. 

It is worth to mention that this definition is not always consistent with the nature of the macromolecular assembly when applying to nucleic acids. For example, from all different types of quadruplex nucleic acids only quadruplex monomers are covered by lUPAC definition of tertiary structure being a single chain of DNA or RNA. However, also the quadruplexes with higher molecularity of the formed structures (dimers, tetramers) belong to this important tertiary structure family. 

The discovery, by the combined use of crystallography and CPMAS NMR, of the dynamic properties of 3,5-dimethylpyrazole (an H-bonded trimer, cf. 122) in the solid state opened a new field of research (85JA5290,92JA9657). Other cyclic structures, dimers like (121) and tetramers like (123) were discovered (94JHC695). 15N CPMAS (with labeled derivatives) proved to be superior to 13C CPMAS. 

One property of hydrophobic interactions is that they tend not to be specific. In other words (and as evident in natural coiled-coil structures), the basic coiled coil pattern HPPHPPP is compatible with a number of helix-bundle quaternary structures. Dimeric, trimeric, tetrameric, penta-meric, and dodecameric coiled coils are all known as are homomeric and heteromeric complexes and topologies with parallel, antiparallel, or mixed arrangements of helices (Burkhard et at, 2001 Gruber and Lupas,... 

Anionic organic complexes of Mo have been immobilized on LDHs. For example, a Mo(VI)02 complex containing 2-mercapto-2,2-diphenyl-ethanoate ligands (14) was supported on ZnAl LDH and used for the catalytic air oxidation of thiols (269-271). Although the homogeneous dioxoMo complex has some catalytic activity, it is rapidly deactivated as a result of the formation of dimers. By intercalation of the complex in an LDH structure, dimerization could be avoided, resulting in improved longevity. 

Table 56 Structures Dimeric Cobalt(III)-Superoxo Complexes...

The value of Atjts reflects the amplitude of the structural dimerization. 

Figure 4 (a) Fermi surface (schematic) and band structure for (TMTSF)2X (after Ref. 32) and for p(ET)2X (after Ref. 32b) (b) schematic illustration of the structural dimerization giving rise to an half-filled upper band in (TMTSF)2X compounds. 

A one-dimensional band with band filling defined by p (0.5 for the TM2 salts forgetting about the structural dimerization) and a molecular volume V would lead to... 

Comparison of Crystal and Solution Structures - Dimerization and Ligand Binding 230... 

The quantitative formation of a single structural dimer indicates that the photoreaction is strictly controlled by the crystal lattice although the final photoproduct is amorphous. 

Tyrosine kinase receptors These receptors exist in a monomer-dimer equilibrium. The dimer, which is sta-bihzed upon ligand binding, is the signaling structure. Dimer formation stimulates catalytic activity and results in intermolecular autophosphorylation within the dimer and triggers signahng cascades that lead to the phosphorylation of cytoplasmic substrates (insulin receptor as example. Figure 3.1). The increase in phosphorylation of tyrosine residues of intracellular proteins either increases or decreases their activity, particularly that of protein kinases or protein phosphatases that often play a crucial role in the regulation of cellular function. 

Some pyrones of the general Kawa structure dimerize on irradiation, even under day light. Although the double bond in the side chain at C6 is. 

The presence of extracellular-type SOD, though of different structure (dimers of 18 kDa), has been reported in plants [12]. 

Indirect reaction Reactions of tannins and anthocyanins with ethanal, formed from ethanol by oxidation of the medium. The ethyl crossbond acts as a bonding agent between the two groups of molecules. The pigments formed are mauve in color, with very variable structures (dimers, trimers, etc.). 

The structure of the kinesin monomer is classified into the three subdomains—head, neck-linker, and tail (see Figure I.IA). The head domain (residue 1-323) contains a nucleotide-binding pocket, a catalytic site, which controls the conformational state of the neck-linker (residue 324-338) made of 15 amino acids. The neck-helix domain (residues from 339 to the C-terminus), extended from the neck-linker, forms an alpha-helical structure dimeric kinesins are made via coiled-coil interactions between the neck-helices from two monomers (see Figure I.IA). 

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