Biomolecular Self-Assembling Materials Scientific and Technological Frontiers (1996) / Chapter Skim
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Pages 8-17
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From page 8... ...
· Lyotropic liquid crystals~3 exhibit a key characteristic of biomolecular self-assembly in that a local molecular feature the amphiphilic nature of the constituent molecules generates self-organized structures that may consist of units of mesoscopic size, which are very large compared to molecular dimensions. For example, lamellar Iyotropic phases are composed of stacks of fluid lipid membranes separated by a solvent.
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From page 9... ...
These polymeric micelles have many of the rheological properties of polymers with covalently bonded backbones, but their lengths are determined by equilibrium thermodynamics rather than being fixed. An interesting example of a self-assembling structure is the tubule, a hollow phospholipid bilayer cylinder morphologically similar to a soda straw (Figure 41.
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From page 10... ...
Two of the tools of molecular biology, namely recombinant DNA and genetic engineering techniques, now make it possible to construct monodisperse, highly specific polymers. For example, both polyesters and polyamides (i.e., protein polymers)
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From page 11... ...
The resulting recombinant DNA is then introduced into the host cell population, cells are grown in large numbers, and protein production is induced. To date, this approach has been used successfully to produce a variety of natural proteins, as well as dozens of wholly artificial protein-like polymers.~9 It is now relatively routine to use bacterial hosts to produce multigram quantities of polymers with degrees of polymerization up to 1000 and molecular weights up to 100,000.
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From page 12... ...
Moreover, dragline silk exhibits the unusual behavior that the strain required to cause failure actually increases with increasing deformation. This property is particularly advantageous because webs need excellent energy-absorbing capability to capture flying prey.
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From page 13... ...
The consensus crystalline repeat in two silk proteins has recently been identif~ed.22 Cloning and expression of the gene for spider dragline silk to facilitate production of large quantities of synthetic silk are now under investigation.23 Another important use of 13 FIGURE 6 Diagram of the proposed model for the molecular arrangement of alanine residues in a fiber of spider dragline silk. Highly oriented alanine-rich crystals of p-sheets (rectangles)
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From page 14... ...
silanes bound to a variety of metal oxide surfaces (especially SiO2) , and carboxylic acids adsorbed on basic oxides (e.g., Alloy.
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Neural synaptic integration in planar neural arrays can also be mediated by SAMs, and the pattern of their interconnections can be controlled by the modification of surface properties. The affinities of surfaces for protein adsorption are also easily modifiable using SAMs.
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From page 16... ...
A notable example of a membrane-associated protein is bacteriorhodopsin (bR) ,30 which embodies two functions of membrane proteins, energy transduction and active ion transport.3~ This protein, which acts as a photon-induced proton pump, self-assembles into a two-dimensional crystalline patch in the lipid bilayer plane of the plasma membrane of the bacterium Halobacterium halobium.
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From page 17... ...
Mesoporous metallic surface films have also been generated via molecular templating, by employing the selfassembled two dimensional crystalline protein arrays of bacterial cell walls as patterning elements. 17 Biomotors Much of the molecular transport in biological systems occurs not by diffusion but by active transport by biomotors.34 Such systems do not conform to our definition of self-assembly because the biomotors are driven by chemical energy input A....
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