A bacterial sensing system that responds selectively to antimonite and arsenite has been investigated. The bacteria used in these studies have been genetically engineered to produce the enzyme beta-galactosidase in response to these ions. This is accomplished by using a plasmid that incorporates the gene for beta-galactosidase (reporter gene) under the control of the promoter of the ars operon. This plasmid also encodes for the ArsR protein, a regulatory protein of the ars operon, which, in the absence of antimonite or arsenite, restricts the expression of beta-galactosidase. In the presence of antimonite or arsenite the ArsR protein is released from the operator/ promoter region of the ars operon and beta-galactosidase is expressed. The activity of this enzyme was monitored electrochemically using p-aminophenyl beta-D-galactopyranoside as the substrate. The bacterial sensing system responds selectively to arsenite and antimonite (and to a lesser extent arsenate) and shows no significant response to phosphate, sulfate, nitrate, and carbonate.

The coupling of screen-printing and laser micromachining technology has been used to create a nanovial with "built-in" working and reference electrodes. The volume of the nanovial was calculated to be 7.2 nL using dimensions determined by SEM. The electrochemical nanovial was characterized using the ferri/ferrocyanide redox couple. Cyclic voltammetry and chronoamperometry experiments were performed with electrochemical nanovials utilizing 5% (v/v) glycerin in the solutions and a humidified headspace to control evaporation of the small-volume samples. Chronoamperometry experiments gave results consistent with a diffusion-limited process and revealed a working electrode surface area of 2.6 x 10(4) micron 2. The ultrasmall-volume cells represent a simple, reliable, low-cost approach for the fabrication of complete electrochemical nanovials.

Cytochrome c peroxidase (CCP) adsorbed at (sub)monolayer surface coverage on edge-oriented pyrolytic graphite (EPG) is being used as a model system for determining the effects of immobilization on the kinetic properties of an enzyme and for developing molecular insight into enzymatic electrocatalysis.

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The Belgrade rat has a microcytic, hypochromic anemia inherited as an autosomal recessive trait (gene symbol b). Transferrin-dependent iron uptake is defective because of a mutation in Nramp2 (now DMT1, also called DCT1), the protein responsible for endosomal iron efflux. Hence, Belgrade reticulocytes are iron deficient. We show that a chromatographic method is able to measure the amount of 'free' heme in reticulocytes. Most of the 'free' heme is the result of biosynthesis. Succinylacetone, an inhibitor of heme synthesis, decreases the level of 'free' heme and cycloheximide, an inhibitor of globin synthesis, increases the 'free' heme level. In a pulse-chase experiment with 59Fe-transferrin, the 'free' heme pool behaves as an intermediate, with a half-life of just over 2 h. Belgrade reticulocytes contain about 40% as much 'free' heme as do heterozygous or homozygous reticulocytes. This deficiency of 'free' heme slows initiation of translation in Belgrade reticulocytes by increasing the level of an inhibitor of initiation. Thus the Belgrade rat makes a whole animal model available with chronic heme deficiency.