Nanoparticles: Scaffolds for Molecular Recognition

Monolayer and mixed-monolayer protected clusters (MPCs and MMPCs) have great potential to combine molecular functionality with the intrinsic properties of nanometer-sized scaffolds. This synergy can be used to create complex functional devices, including redox-active, electronic, or magnetic storage devices, solution-based sensors, and highly efficient catalysts. This review outlines some of the recent developments in nanoscale receptors based on synthetic and nonbiological recognition elements. In these nanoparticle systems, molecular recognition is achieved by covalent attachment of receptors on the nanoparticles coupled with noncovalent interactions to target substrates. Synthetic host-guest systems, hydrogen bonding, change in redox states, pi-pi stacking, rotaxane formation, and ion recognition are the main topics covered in this review.

Gold glyconanoparticles as new tools in antiadhesive therapy

Gold glyconanoparticles (GNPs) have been prepared as new multivalent tools that mimic glycosphingolipids on the cell surface. GNPs are highly soluble under physiological conditions, stable against enzymatic degradation and nontoxic. Thereby GNPs open up a novel promising multivalent platform for biological applications. It has recently been demonstrated that specific tumor-associated carbohydrate antigens (glycosphingolipids and glycoproteins) are involved in the initial step of tumor spreading. A mouse melanoma model was selected to test glyconanoparticles as possible inhibitors of experimental lung metastasis. A carbohydrate-carbohydrate interaction is proposed as the first recognition step for this process. Glyconanoparticles presenting lactose (lacto-GNPs) have been used successfully to significantly reduce the progression of experimental metastasis. This result shows for the first time a clear biological effect of lacto-GNPs, demonstrating the potential application of this glyconanotechnology in biological processes.

Complementary nucleobase interaction enhances peptide-peptide recognition and self-replicating catalysis

The availability of the complementary interaction of nucleobases for influencing the formation of peptide architectures was explored. Nucleobases were incorporated as additional recognition elements in coiled-coil peptides by employing nucleobase amino acids (NBAs), which are artificial L-alpha-amino gamma-nucleobase-butyric acids. The effect of the base-pair interaction on intermolecular recognition between peptides was evaluated through a self-replication reaction. The self-replication reactions of the peptides with complementary base pairs such as thymine-adenine or guanine-cytosine at the g-g' heptad positions were accelerated in comparison with those of the peptides with mismatched base pairs or without nucleobases. However, thymine-adenine pairs at the e-e' positions did not enhance the self-replication. In the presence of a denaturant, the enhancement effects of complementary base pairs on the reaction disappeared. Thermal denaturation studies showed that the thymine-adenine pairs contributed to stabilization of the coiled-coil structure and that the pairs at the g-g' positions were more effective than those at the e-e' positions. The peptide-peptide interaction was reinforced by complementary nucleobase interactions appropriately arranged in the peptide structure; these led to acceleration of the self-replication reactions.