Molecular rods

Molecular rods including heterocyclic fragments, in particular pyridine and porphyrine residues 99CRV1863. 

Covalent attachment of adamantane molecules is a key strategy to string them together and construct molecular rods. The McMurry coupling reaction was employed to obtain polyadamantane molecular rods (see Fig. 35) [170]. As another example, synthesis of tetrameric 1,3-adamantane and its butyl derivative has been reported [171] (see Fig. 36). 

Figure 35 Polyadamantane molecular rods. Taken from Ref. [170] with permission.

Adamantane can be used to construct peptidic scaffolding and synthesis of artificial proteins. It has been introduced into different types of synthetic peptidic macrocycles, which are useful tools in peptide chemistry and stereochemistry studies and have many other applications as well. Introduction of amino acid-functionalized adamantane to the DNA nanostmctures might lead to construction of DNA-adamantane-amino acid nanostmctures with desirable stiffness and integrity. Diamondoids can be employed to constmct molecular rods, cages, and containers and also for utilization in different methods of self-assembly. In fact, through the development of self-assembly approaches and utilization of diamondoids in these processes, it would be possible to design and constmct novel nanostmctures for effective and specific carriers for each dmg. 

Fig. 5. [3]Pseudorotaxane dendrimers from complexation of the dendrophanes and molecular rod with rigid oligo(phenylacetylene) spacers and terminal steroid units... 

Fig. 7. [4] Pseudorotaxane dendrimers from dendrons with a macroq cle at the focal point and a triply branched molecular rod...

Yam VW-W, Wong KM-C (2005) Luminescent Molecular Rods - Transition-Metal Alkynyl Complexes. 257 1-32... 

Heteroaryl groups are present in the 4-pyridyl-ethynyl compounds81,99,100 and their extended variants with C=C-C6H4-C=C-pyr-4 ligands.81,99 These compounds can be quaternized with Mel or coordinated to a metal complex at their terminal pyridyl functions to give species addressed as molecular rods or molecular wires.81,99 Similar reactions were carried out with 3-phenanthrolinyl-ethynyl complexes,62 and special examples are also known with R based on calixarenes.51... 

Lortscher E, Elbing M, Tschudy M, von Hanisch C, Weber HB, Mayor M, Riel H (1997) Charge transport through molecular rods with reduced 7i-conjugation. ChemPhysChem 9 2252-2258... 

In summary, the formation of silk fibers involves superstructures such as, possibly, micelles and/or molecular rods (Akai, 1998 Jin and Kaplan, 2003 Knight and Vollrath, 2002) that are dependent on the packing and conformation of the individual protein units. The relationship, however, between the shapes of these superstructures and the various forms of protein conformation remains elusive (Valluzzi and Jin, 2004). Seeking to clarify this issue we will examine, in Section II.B, the role of shape and extended network formation modulating solubility, stability, and assembly. 

The basic extensins. These are hydroxyproline-, lysine- and tyrosine-rich glycoproteins consisting of rigid molecular rods about 80 nm long (14,15), bearing short mono- to tetrasaccharide side-chains (2,14). When newly secreted they bind ionically to the acidic polysaccharides of the cell wall and can be extracted with cold salt solutions later they become much more resistant to salt-extraction and are said to be covalently bound, probably via dimerization of their tyrosine residues to form isodityrosine (15). 

Random-coil sequences left in a predominantly helical chain can be a cause of flexibility of the molecular rod unless they are too short, and will lead to deviations of the shape-dependent properties of the molecule from those expected for rigid rod. Too short a random-coil sequence may not act as a flexible joint partly because of hindered rotations of the single bonds contained... 

Miller and Flory (43) calculated of a-helices by taking bond-angle fluctuations into account. This approach gives the molecular rod a flexibility similar to that of wormlike chains but retains the a-helical conformation of the chain. Thus, in a sense, it may be regarded as a refinement of the treatment of Moha et al. The calculated results gave a nonlinear chain-length dependence of experimental results shown in Fig. 21. 

A few transmembrane molecular rods having different lengths and terminal shapes and moving freely by lateral diffusion may bind to a given receptor-transmitter on one side (left) of the membrane in a configuration in the membrane plane and in a displacement perpendicular to the membrane that will depend on the disposition and depth of the binding sites on the transmitter. This will impose on the... 

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