S-layers as templates

VI. S-LAYER AS TEMPLATES FOR THE FORMATION OF REGULARLY ARRANGED NANOPARTICLES... 

Douglas and coworkers were the first one that described a bottom-up approach based on S-layers as templates for the formation of perfectly ordered arrays of nanoparticles [128]. The S-layer lattice was used primarily to generate a nanometric lithographic mask for the subsequent deposition of metals. In this approach a thin Ta-W film was deposited... 

VIII. S-Layers as Templates in the Formation of Regularly Arranged Nanoparticles... 

It should be stressed that with S-layers as molecular templates the formation of superlattices with a wide range of interparticle spacings as well as with oblique, square, or hexagonal lattice symmefiy becomes possible. This is particularly important for the development of nanometric electronic or optical devices since isolated S-layer subunits have shown the inherent capability to recrystallize on a great variety of solid supports including structured semiconductors [129,131]. 

Finally, feasibility studies have clearly demonstrated that S-layer technologies have a great potential for nanopatteming of snrfaces, biological templating, and the formation of arrays of metal clusters, as required in nonlinear optics and molecular electronics. 

A crystalline bacterial surface layer with a well defined geometry of Sporosarcina ureae (so-called S layer) is used as a protein template (unit cell 13.2 nm x 13.2 nm) on a cell membrane. Noble metal nanoclusters (Pt or Pd) are deposited chemically to produce nanostructures. The spatial distribution of noble metal nanoclusters is characterized by transmission electron microscopy (TEM). 

Fig 9.29 illustrates Zn determination in a Zn binding protein in a selected protein spot after separation of the proteins of an S layer used as biomolecular template, as described above, by 2D gel measured by LA-ICP-SFMS at medium mass resolution (m/Am = 4000). ° The Zn ion intensity in the protein spot (compared with the background signal in the gel blank) was measured at three different positions in the selected spot. Using LA-ICP-SFMS, the highest Zn intensity was found in the middle of the protein spot investigated. Additional measurements by MALDI-MS on Zn containing protein spot in 2D gel can be useful to identify the structure of the protein. ... 

Study of nanoscale biological systems and phenomena, the use of biological components in nanotechnological applications and the synthesis or construction of nanometre scale mimics of biological entities. Examples include the use of DNA for molecular computing, or as a nanoscale structural scaffold, and the temptation of nanostructures using bacterial S-layers (Section 14.6.2). With these ideas in mind we turn first to templated morphosynthesis the chemical synthesis of nanoscale morphologies that often mimic complex structures found in the Natural world. 

The S-layer of S. ureae ATCC 13881 has been reported to be an excellent biotemplate for fabrication of highly ordered metal cluster arrays. Pt was deposited onto the isolated protein sheets by first incubating the metal salt with the S-layer followed by a reducing step to obtain metallic Pt particles (Mertig et al., 1999). As a result, highly ordered nanocluster arrays were formed on the protein template reproducing its square symmetry. 

Nanowires in the microchip industry and as nanowaveguides for electromagnetic radiation, for solvent evaporation of hydrophobic nanoparticle molecular crosslinking in colloidal aggregates and templates [45-47], and in assemblies using biomacromolecules [48] such as DNA [49] and bacterial S-layer proteins [50]... 

Material templating, assembly, and crystallization can be achieved using organized biomolecular systems such as protein cages [23-26], lipid assemblies [27], bacterial S-layers [28], and DNA [29,30]. This research field has attracted growing attention, and several reports and review articles have been published in this regard [31,32]. 

The presence of S-layer lattices significantly enhanced the stability of the liposomes against mechanical stress such as shear forces or ultrasonication and against thermal challenges [151]. The S-layer lattices have been further exploited as a template for chemical modifications and as matrix for the immobilization of macromolecules, such as ferritin (Figure 17) [148]. After biotinylation of histidine or tyrosine residues [153] which do not disturb the stmctural integrity of the oblique... 

The wealth of information obtained on the general principles of crystalline bacterial cell surface layers, particularly on their structure, assembly, surface, and molecular sieving properties have revealed a broad application potential. Above all, the repetitive physicochemical properties down to the subnanometer-scale make S-layer lattices unique self-assembly structures for functionalization of surfaces and interfaces down to the ultimate resolution limit. S-layers that have been recrystallized on solid substrates can be used as immobilization matrices for a great variety of functional molecules or as templates for the fabrication of ordered and precisely located nanometer-scale particles as required for the production of biosensors, diagnostics, molecular electronics, and nonlinear optics [2,3,6]. 

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