© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

3.5.7.2 Solid Mosaic Model

In the solid mosaic receptor model, the precise shape and charge distribution of the target molecule is already known. Working from this information, a set of diamondoid components could be fabricated which, when fitted together like a Chinese puzzle box, create a solid object having a cavity in the precise shape of the optimum negative image of the target molecule (Fig. 3.12A). The mosaic may contain point charges, voids, stressed surfaces, or dislocations to achieve fine positional control. Mosaic components may be as small as individual atoms, so this model is conceptually similar to 3-D printing or raster-scan techniques in which the desired cavity formation is constructed atom by atom inside a nanofactory (Fig. 3.12B; Chapter 19). This model, like the imprint model, cannot easily be reconfigured once it has been constructed because each of the many unique parts may contribute to the entire structure. The construction of receptors from parts of fixed size and shape is crudely analogous to members of the heterodimer receptor class (a two-component receptor) such as GABA_B.²⁶⁸⁷

M. Reza Ghadiri has designed a protein mosaic model using cyclic peptides that assemble spontaneously into nanotubes of predefined diameter; incorporation of hydrophobic amino acid side chains on the outside of these tubes leads to spontaneous insertion into bilayers, allowing the tubes to function as transmembrane ion channels.²⁴⁴⁰ Other examples of mosaic model receptors are mesoporous silica filters with functionalized organic monolayers forming 36 nm sievelike pores,^693,1522 and zeolites and zeolitelike molecular sieves. Zeolites are artificial crystal structures with precise and uniform 0.4-1.5 nm internal void arrays which can also be used as shape-selective catalysts able to favor one product over another that differs in size by as little as 0.03 nm, such as pxylene and oxylene.⁴³⁰ By 1998, rational de novo computational design of artificial zeolite templates^431,432,934 and crystal engineering^695,948 had begun.

Last updated on 7 February 2003