Trimer conformation

For methanol clusters [36], it was found that the dimer is linear, while clusters of 3 and 4 molecules exist as monocyclic ring structures. There also is evidence that there are two cyclic ring trimer conformers in the molecular beam. 

Alzheimer s Disease. Figure 1 A(3 monomers can self-associate to form dimers, trimers and higher oligomers. Globular structures of synthetic A(342 are known as A(3-derived diffusible ligands (ADDLs) (3-12-mers of A(3). These structures are similar to the smallest protofibrils and represent the earliest macromolecular assembly of synthetic A(3. The characteristic amyloid fiber exhibits a high beta-sheet content and is derived in vitro by a nucleation-dependent self-association and an associated conformational transition from random to beta-sheet conformation of the A(3 molecule. Intermediate protofibrils in turn self-associate to form mature fibers. 

Westwood, J.T. Wu, C. (1993). Activation of Drosophila heat shock factor Conformational change associated with monomer to trimer transition. Mol. Cell. Biol. 13, 3481-3486. 

Fig. 2.25 Conformational preferences and eight-membered turn motif of jS -peptides with 1 -aminomethylcyclopropanecarboxylic acid residues. X-ray crystal structures of dimer no, trimer m and tetramer 112 together with a model constructed using...

Binding of the receptor induces a rapid conformational change (switch) in the G-protein trimer. This is transmitted to the nucleotide binding site, about 3 nm away, and results in a dissociation of bound GDP. 

Dialkyl zinc compounds form phosphine complexes of formula RZnP(SiMe3)2 on addition of one equivalent of bis(trimethylsilyl)phosphine. Solution and solid-state studies showed that the complexes are dimeric or trimeric in solution or the solid state. Bis(trimethylsilyl)phosphido-methylzinc crystallizes as a trimeric molecule with a Zn3P3 core in the twist-boat conformation. Bis(trimethylsilyl)phosphido- -butylzinc, shows a similar central Zn3P3 fragment. The sterically more demanding trimethylsilylmethyl substituent forms a dimeric species of bis(trimethylsilyl) phosphido-trimethylsilylmethylzinc. Solution studies of bis(trimethylsilyl)phosphido- .vo-propyl-zinc demonstrate a temperature-dependent equilibrium of the dimeric and trimeric species and the crystalline state contains a 1 1 mixture of these two oligomers. A monomeric bis(trimethyl-silyl)phosphido-tris(trimethylsilyl)methylzinc has also been synthesized.313... 

The above-mentioned [Hg(P—Z-Bu2)2]2 has been obtained in a phosphide-transfer reaction between HgMe2 and Ga(P-z-Bu2)3. If CdMe2 and Ga(P—/-Bu2)3 are reacted, the product is the trimeric [MeCd(P-/-Bu2)2]3 with a six-membered Cd3P3 ring in twist-boat conformation and exocyclic Cd—Me bonds thus, Cd achieves near-planar, three-coordinate geometry. The Cd—P bond lengths in the ring are all similar (rav(Cd—P) 258.5 pm) in solution these Cd—P bonds... 

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