Abstract: A Si chip (7 x 7 x 0.4 mm) was constructed in two parts; one is the gas-sensitive area and the other a temperature control area. The former consisted of two noble metal films (Au and Pd) deposited on titanium oxide. The latter was made up of a Ni-chrome heater and Ni thermo-sensor having a positive thermal coefficient. The heater, thermo-sensor and bonding pads were prepared by means of RF sputtering and photolithography on a Si substrate by the method of Toda, (Bunseki Kagaku, 1990, 39, 611). On the substrate a Ti film was deposited and its surface was oxidized at 500°C for 70 min in a stream of O2. Au and Pd films were deposited separately on the titanium oxide by means of evaporation. Test gases of various concentrations were prepared and allowed to flow over the sensor in a chamber at a controlled humidity of 65% (details given). For H2, the Pd-side unit exhibits a response related to the gas concentration while the Au-side shows no response. For phosphine, the Au-side exhibits an extremely high sensitivity while the Pd-side shows only a small response, even at 200 ppm.

Abstract: A continuous-flow method was developed for determining the stoichiometry of the gastric proton pump H,K-ATPase (EC 3.6.1.36) in its hydrolysis of ATP and translocation of H+ and the K+ congener 86Rb+. H,K-ATPase-containing vesicles which had been isolated from pig gastric mucosa were incubated at 37°C for 2 h in 150 mM 86RbCl, 0.5 mM ethylenebis(oxyethylenenitrilo)tetra-acetic acid and 3 mM 2-(N-morpholino)ethane sulphonic acid (Mes) adjusted to pH 6.1 with Tris, and then applied onto a 0.45 micron pore size cellulose acetate filter. The immobilized vesicles were superfused with 0.15 mM Mes/Tris buffer, pH 6.1, containing 150 mM choline chloride and 0.2 mM MgCl2. After changing to a medium containing 0.1 mM ATP, the amounts and rates of H+ uptake, 86Rb+ efflux and ATP hydrolysis were measured. The initial ratio of Rb+ transported to ATP hydrolyzed gave values of 0.96±0.26 (mean±SD, n = 28). The initial ratio of ATP-dependent Rb+ efflux to H+ uptake gave values of 0.92±0.28 (mean±SD, n = 28). The Mg-ATPase activity was measured in vesicles which had been incubated with choline chloride instead of RbCl. This activity was 15.8±8.7% (mean±SD) of the total ATPase activity in the initial fractions used for calculation of the stoichiometry. It is argued that this Mg-ATPase may be an intrinsic activity of the H,K-ATPase and that the relation between these activities is dependent on the amount of K+ (or Rb+) present in the assay.