| abstract |
Device whose electrical conductivity changes in response to change in the surrounding conditions comprises an enzyme-coated membrane immersed in an electrically conductive liq. medium contg. a substrate which undergoes an enzyme-catalysed reaction to produce at least one prod. which alters the conductivity of the membrane. The improvement comprises selecting the effective concn. of enzyme mols. on the active surface of the membrane and the effective concn. of substrate mols. (or clusters thereof) in the liq. medium, taking into account the diffusion rate of the substrate and the rate of the enzyme- catalysed reaction, so as to produce pulsed changes in the conductivity of the membrane. The device can be used to monitor enzyme reactions or to measure pH, temp, electric filed strength or flow rate. The device operates with much lower enzyme and substrate concns. than known devices of this type (cf. Experientia, 28, 256, 1972). |