Cyclic nucleotide-gated (CNG) ion channels mediate sensory signal transduction in photoreceptors and olfactory cells. Structurally, CNG channels are heterotetramers composed of either two or three homologue subunits. Although it is well established that activation is a cooperative process of these subunits, it remains unknown whether the cooperativity is generated by the ligand binding, the gating, or both, and how the subunits interact. In this study, the action of homotetrameric olfactory-type CNGA2 channels was studied in inside-out membrane patches by simultaneously determining channel activation and ligand binding, using the fluorescent cGMP analogue 8-DY547-cGMP as the ligand. At concentrations of 8-DY547-cGMP < 1 microM, steady-state binding was larger than steady-state activation, whereas at higher concentrations it was smaller, generating a crossover of the steady-state relationships. Global analysis of these relationships together with multiple activation time courses following cGMP jumps showed that four ligands bind to the channels and that there is significant interaction between the binding sites. Among the binding steps, the second is most critical for channel opening: its association constant is three orders of magnitude smaller than the others and it triggers a switch from a mostly closed to a maximally open state. These results contribute to unravelling the role of the subunits in the cooperative mechanism of CNGA2 channel activation and could be of general relevance for the action of other ion channels and receptors.

We report a detailed investigation of the processes of the surface segregation in correlation with the wetting properties of perfluoroalkyl end-functionalized linear aromatic oligoesters. We have compared properties of films containing different fluorine concentration prepared by the spin-coating technique and by melting of polymer grain onto the supported substrate. We demonstrate that both methods can be used for the preparation of highly hydrophobic and oleophobic surfaces. Obtained layers possess high value of n-hexadecane advancing contact angle and low contact angle hysteresis. Moreover, oligoester films with the surface energies as low as 11 mJ/m 2 were prepared with 10.7 wt % of fluorine in the system and possessed higher oleophobicity than Teflon AF. We showed that the advantages of use of melting of polymer grain are higher surface enrichment and closer packing of perfluorinated species and, as a result, a higher hydro/oleophobicity, especially at lower F contents (<6 wt %). This is a first report about an influence of preparation method onto the surface properties of perfluorinated polymers.

Activation of microglial cells, the resident macrophages of the brain, occurs rapidly following brain injury. De-ramification, i.e. transformation from ramified into amoeboid morphology is one of the earliest manifestations of microglial activation. In the present study, we identified the physiological mechanisms underlying microglial de-ramification induced by lysophosphatidylcholine (LPC

No abstract