Response characteristics of the glucose-sensitive field-effect transistor. Computer simulation of the effect of gluconolactonase coimmobilization in a glucose oxidase membrane

The bienzyme system consisting of glucose oxidase and gluconolactonase was investigated using a conventional diffusion-kinetics model for an enzyme-modified field-effect transistor (FET) to clarify the effect of gluconolactonase coimmobilization in a glucose oxidase membrane on the steady-state response amplitude of a glucose sensor based on a FET. The model includes spontaneous and enzymatic hydrolysis reactions of d-glucono-δ-lactone and it elucidated the following experimental results: a glucose sensor with a membrane (about 1 μm in thickness) coimmobilizing these enzymes showed a sufficient response amplitude, whereas without coimmobilization of gluconolactonase no detectable response was observed up to 3 mM glucose; and the response amplitude depended strongly on the amount of lactonase in the membrane. The model also predicted an optimum enzyme ratio for coimmobilization in a membrane.     

α-Phenylselenenylation of zirconium or aluminum enolates

Zirconium or aluminum O-enolates undergo selenenylation with PhSeBr to give α-(phenylselenenyl) ketones in good to excellent yield.     

Glucose sensor based on a field-effect transistor with a photolithographically patterned glucose oxidase membrane

A photopolymer solution consisting of polyvinylpyrrolidone and 2,5-bis(4′-azido-2′-sulfobenzal)cyclopentanone is used to make a patterned glucose oxidase membrane for a FET-glucose sensor by photolithography. A small patterned glucose oxidase membrane, 0.2 mm wide and 1 mm long, is made on the gate surface of an ISFET by developing a photocross-linked glucose oxidase membrane with aqueous 1–3% glutaraldehyde solution. The optimum composition of the enzyme/photopolymer solution is described. The sensor with the patterned membrane showed linear response to glucose concentration from 0.3 to 2.2 mM and useful response up to 5 mM.     

Neutral lipid enzyme electrode based on ion-sensitive field effect transistors

An enzyme electrode for neutral lipid determination based on hydrogen ion-sensitive field effect transistors (pH-FET's) is described. The electrode is composed of two pH-FET's with an immobilized lipase membrane on one pH-FET, and a platinum wire. Triglycerides are solubilized with 10% (v/v) Triton X-100. The electrode is used to determine triglycerides over wide concentration ranges with response times of ca. 2 min. Relations between signal and the logarithm of the concentration are linear over the ranges 100–400 mM triacetin, 3–50 mM tributylin and 0.6–3 mM triolein. In the case of triolein, the detection limit is 9 μg ml^?1 (signal/noise = 3:1). The effect of Triton X-100 on the electrode response is discussed.     

Deformation of a submanifold in a Euclidean space with fixed gauss image: II

Deformation of an m-dimensional submanifold immersed in a Euclidean n-space is studied when the Gauss image does not move pointwise. The present paper is the third one and contains deformations where the tensor of deformation satisfies some differential equations, normal deformations and deformations of totally-real submanifolds in a complex space.     

Characteristics of 20 year old iodine cell and compact iodine stabilized laser

Spectral quality and reliability of four kinds of¹²⁷ I ₂ cells for an wavelengtn standard were investigated. A 20 year old 10 cm long sealed off iodine cell has shown its long life and had sufficient absorption characteristics comparable to the newly made three cells in regard to spectral line width and signal-to-noise ratio of the absorption signal. A dispersion of absolute frequencies of the three cells including the 20 year old cell is in a range of 35 kHz, which is equivalent to a frequency reproducibility of 7.4X10^-11. A compact iodine stabilized 633 nm He-Ne laser with a 23 cm long resonator and 4 cm iodine cell has been developed. Its frequency stability has been estimated to be 9X10^-13 by the Allan deviation at integration time of 4000 s. The laser supplies 14 wavelength standards being locked at iodine absorption lines from a ton.     

On some property of an irreducible subalgebra of the general linear Lie algebra gl(n,R)

Summary A subalgebrag ofgl(n, R) which admits no proper invariant subspace in Rⁿ and contains a subalgebra of a special kind is studied. It is concluded that only four cases are possible if n is even, and only two if n is odd. To Enrico Bompiani on his scientific Jubilee     

Arsenic Compounds Accumulated in Sedimentary Microorganisms Cultivated in Media Containing Several Arsenicals

Sediments, as sources of microorganisms, were added to two kinds of media, 1/5 ZoBell 2216E and a solution of inorganic salts, which contained inorganic arsenic(III), inorganic arsenic(V), methanearsonic acid, dimethyl- arsinic acid, trimethylarsine oxide, tetramethylarsonium salt or arsenocholine. After 17 days of incubation at 20 °C, the arsenicals that had accumulated in the microorganisms were analysed by high-performance liquid chromatography (HPLC). While the more toxic arsenicals [inorganic arsenic(III), inorganic arsenic(V), methanearsonic acid, dimethylarsinic acid] were not converted in the microorganisms, trimethylarsine oxide and tetramethylarsonium salt were considerably degraded to inorganic arsenic(V), and arsenocholine to arsenobetaine. Arsenobetaine that had accumulated in the microorganisms was extracted and confirmed by thin-layer chromatography (TLC) and fast atom bombardment (FAB) mass spectrometry.     

A flow-through cell for use with an enzyme-modified field effect transistor without polymeric encapsulation and wire bonding

A new type of flow-through cell for an enzyme-modified field effect transistor (FET) is described. The cell makes it possible to use a FET without polymeric encapsulation and wire bonding. Electrical evaluation of a FET used with the flow cell demonstrates that the flow cell has no practical problems causing sensor malfunctions. The noise and drift levels of tbe FET sensor with the flow cell are shown to be similar to those of an epoxy-encapsulated FET sensor. The application of the flow cell with a urease-modified FET is described. Useful responses are obtained for 0.25–50 mg l^?1 urea with relative standard deviations of <3%.