Chemical Information Processing by a Responsive Chemical System.

Nature has an extraordinary capacity to precisely regulate the chemical reactivity in a highly complex mixture of molecules that is present in the cell. External stimuli lead to transient up- and downregulation of chemical reactions and provide a means for a cell to process information arriving from the environment. The development of synthetic chemical systems with life-like properties requires strategies that allow likewise control over chemical reactivity in a complex environment. Here, we show a synthetic system that mimics the initial steps that take place when a natural signal transduction pathway is activated. Monophosphate nucleosides act as chemical triggers for the self-assembly of nanoreactors that upregulate chemical reactions between reagents present at low micromolar concentrations. Different nucleotides template different assemblies and hence activate different pathways, thus establishing a distinct connection between input and output molecules. Trigger-induced upregulation of chemical reactivity occurs for only a limited amount of time because the chemical triggers are gradually removed from the system by enzymes. It is shown that the same system transiently produces different output molecules depending on the chemical input that is provided.

Sequence-selective duplex formation and template effect in recognition-encoded oligoanilines.

A new family of duplex-forming recognition encoded oligomers, capable of sequence selective duplex formation and template directed synthesis, was developed. Monomers equipped with both amine and aldehyde groups were functionalized with 2-trifluoromethylphenol or phosphine oxide as H-bond recognition units. Duplex formation and assembly properties of homo- and hetero-oligomers were studied by 19F and 1H NMR experiments in chloroform. The designed backbone prevents the undesired 1,2-folding allowing sequence-selective duplex formation, and the stability of the antiparallel duplex is 3-fold higher than the parallel arrangement. Dynamic combinatorial chemistry was exploited for the templated synthesis of complementary oligomers, showing that an aniline dimer can template the formation of the complementary imine. The key role of the H-bond recognition confers to the system the ability to discriminate a mutated donor monomer incapable of H-bonding. Sequence selective duplex formation combined with the template effect makes this system an attractive target for further studies.

In vivo prion protein intestinal uptake in fish.

Intestinal uptake of abnormal prion protein (PrPSc), the pathological agent involved in transmissible spongiform encephalopathies (TSEs), has been investigated in rainbow trout (Oncorhynchus mykiss). Experimental procedures were conducted in vivo by immunohistological PrPSc localization in intestine and pyloric caeca after forced feeding of infected material. Results indicate that PrPSc was absorbed by the intestinal mucosa and that it persisted in the fish gastrointestinal tract for up to 3 days in pyloric caeca and for up to 7 days in the distal intestine. It did not remain longer than 15 days in the fish intestine; furthermore, it did not cross the intestinal barrier.