STM studies of ordered (√31x √31)R9° CO islands on Ag(111)

The adsorption behavior of CO on Ag(111) is studied using low-temperature scanning tunneling microscopy. At submonolayer coverage, only single CO molecules are observed upon adsorption at 5 K. A further dosage leads to the formation of islands with various shapes and sizes. In addition, clusters with a diameter of about 11 Å are found that are mobile on the surface at 5 K. Though the position of the CO molecules within these clusters cannot be resolved, their size points to CO hexamers or heptamers. Well-ordered CO islands are observed only after heating the sample to 17 K, whereby two rotational domains with hexagonal (√root 31x √root 31)R9° structure are formed. A structural model is proposed in which CO hexamers represent the fundamental building blocks. The existence of two domains is explained with the alternate CO adsorption on the fcc and hcp places within the hexamers. The (√31 x √31)R9° superlattice is the only well-ordered CO structure found in the temperature range between 5 K and 35 K

Counting electrons transferred through a thin alumina film into Au chains

Low-temperature STM measurements combined with density functional theory calculations are employed to study the adsorption of gold on alumina/NiAl(110). The binding of Au monomers involves breaking of an oxide Al-O bond below the adatom and stabilizing the hence undercoordinated O ion by forming a new bond to an Al atom in the NiAl. The adsorption implies negative charging of the adatom. The linear arrangement of favorable binding sites induces the self-organization of Au atoms into chains. For every ad-chain, the number of transfer electrons from the support is determined by analyzing the node structure of the corresponding highest occupied molecular orbital

Glutathione accelerates sodium channel inactivation in excised rat axonal membrane patches

The effects of glutathione were studied on the gating behaviour of sodium channels in membrane patches of rat axons. Depolarizing pulses from –120 to –40 mV elicited sodium currents of up to 500 pA, indicating the simultaneous activation of up to 250 sodium channels. Inactivation of these channels in the excised, inside-out configuration was fitted by two time constants ( h1=0.81 ms; h2= 5.03 ms) and open time histograms at 0 mV revealed a biexponential distribution of channel openings ( short=0.28 ms; long=3.68 ms). Both, the slow time constant of inactivation and the long lasting single channel openings disappeared after addition of the reducing agent glutathione (2–5 mM) to the bathing solution. Sodium channels of excised patches with glutathione present on the cytoplasmatic face of the membrane had inactivation kinetics similar to channels recorded in the cell-attached configuration. These observations indicate that redox processes may contribute to the gating of axonal sodium channels