Carbonic anhydrases activation with 3-amino-1H-1,2,4-triazole-1-carboxamides: Discovery of subnanomolar isoform II activators.

A series of ureas was prepared by reacting mono- or di- isocyanates with 3-amino-1H-1,2,4-triazole derivatives. The new carboxamides were investigated as activators of two human (h) carbonic anhydrases (CAs, EC 4.2.1.1), the physiologically relevant isoforms hCA I and II, considering the fact that they have structural resemblance to histamine, a well-known CA activator. Highly effective activators were detected in the series, with potency in the low nanomolar and subnanomolar range, depending on the substitution pattern at the 1,2,4-triazole ring and the nature of the linker between the two heterocyclic rings, in the case of the diureas. The most effective hCA II activator (KA of 0.05nM) ever reported has been evidenced in this study. Although CA activators do not have pharmacological applications for the moment, in animal models it has been shown that they enhance cognition, making them interesting for conditions in which CA activity is diminished, such as aging or Alzheimer's disease.

Polarized Water Wires under Confinement in Chiral Channels.

The alignment of water molecules along chiral pores may activate proton/ion conduction along dipolar hydrophilic pathways. Here we show that a simple synthetic "T-channel" forms a directional pore with its carbonyl moieties solvated by chiral helical water wires. Atom-scale simulations and experimental crystallographic assays reveal a dynamical structure of water and electrolyte solutions (alkali metal chlorides) confined in these organic T-channels. Oscillations in the dipole orientation, which correspond to alternative ordering (dipole up-dipole down) of the water molecules with a period of about 4.2 Å (imposed by the distance between two successive carbonyl groups) are observed. When ions are added to the system, despite the strong Coulombic water/ion interaction, confined water remains significantly ordered in the T-channel and still exhibits surface-induced polarization. Cation permeation can be achieved through alternated hydration-dehydration occurring along strongly oriented water wires. The T-channel, which exhibits chirality with strong water orientation, provides an opportunity to unravel novel water-channel systems that share many interesting properties of biomolecular systems.

An artificial primitive mimic of the Gramicidin-A channel.

Gramicidin A (gA) is the simplest known natural channel, and important progress in improving conduction activity has previously been obtained with modified natural gAs. However, simple artificial systems mimicking the gA functions are unknown. Here we show that gA can be mimicked using a simple synthetic triazole or 'T-channel' forming compound (TCT), having similar constitutional functions as the natural gAs. As in gA channels, the carbonyl moieties of the TCT, which point toward the T-channel core and surround the transport direction, are solvated by water. The net-dipolar alignment of water molecules along the chiral pore surfaces influences the conduction of protons/ions, envisioned to diffuse along dipolar hydrophilic pathways. Theoretical simulations and experimental assays reveal that the conduction through the T-channel, similar to that in gA, presents proton/water conduction, cation/anion selectivity and large open channel-conductance states. T-channels--associating supramolecular chirality with dipolar water alignment--represent an artificial primitive mimic of gA.

Dynamic constitutional electrodes toward functional fullerene wires.

Constitutional mesoporous thin-layer electrodes have been used to generate confined fullerene wires allowing a capacitive diffusion of electrons.