Sensors protein-specific

Microelectronic circuits for communications. Controlled permeability films for drug delivery systems. Protein-specific sensors for the monitoring of biochemical processes. Catalysts for the production of fuels and chemicals. Optical coatings for window glass. Electrodes for batteries and fuel cells. Corrosion-resistant coatings for the protection of metals and ceramics. Surface active agents, or surfactants, for use in tertiary oil recovery and the production of polymers, paper, textiles, agricultural chemicals, and cement. 

Fig. 10.3. Acceptor photobleaching analysis of interaction between barley MLO and calmodulin. Barley MLO is a plant-specific integral membrane protein that associates with the cytosolic calcium sensor protein Calmodulin...

In addition to kinase-phosphatase cycles, bacteria use at least two other ATP-dependent regulatory mechanisms.110 In the sensor kinase/response regulator (or "two-component") systems110 111 a sensor protein, upon being allosterically activated, phosphorylates itself (autophosphorylation) on a specific histidyl residue to form an N-phosphohistidine derivative. 

The second messengers may bind to specific sensor proteins inside the cell and trigger responses such as the activation of enzymes. Signal-transduction mechanisms vcill be considered in detail in Chapter 15 and in many other chapters throughout this book. 

Calcium sensor protein also occiurs in the kidney. Specifically, the calcium sensor occurs in the thick ascending loop, where the N-terminal half juts out into the extracellular fluid (not into the lumen of the tubule, but in the space between tubules). When extracellular Ca " ions increase in concentration, the thick ascending loop decreases its rate of calcium resorption (Chattopadhyay et al, 1996 Pearce and Thakkar, 1997 Pearce et al., 1996). The regulatory scenario in the kidney represents a mode of regulating the body s calcium balance that appears completely independent of vitamin D. The overall scenario is that, as extracellular Ca " increases, the parathyroid gland decreases its release of PTH, and the kidney reduces its reabsorption of calcium ions from the developing urine. 

To demonstrate a way of the use of aptamers in design of biomimetic sensors, two examples will be cited from the recent literature. The piezoelectric sensor for protein IgE has been developed with the use of commercially available anti-IgE aptamer oligonucleotide.167 The obtained sensor shows specificity and sensitivity equivalent to these of immunosensor, but for aptamer-based sensor a less decrease of sensitivity after consecutive cycles of analyte binding and regeneration, as well as relative heat resistance and stability over several weeks was shown. A more complex mechanism of sensing was employed in adenosine aptamer-based sensor.168 Detection was based on enzymatic activity measurements by fluorescence polarization with the use of aptameric enzyme subunit, which was a DNA aptamer composed of enzyme-inhibiting aptamer and adenosine-binding aptamer. 

Conventional and novel PKC isozymes are potently activated by phorbol esters, heterocyclic compounds found in the milky sap exuded by plants of the Euphorbiaccae family. This sap was used medicinally as a counterirritant and cathartic agent over the millennia we now know that the active ingredients, phorbol esters, specifically bind to the Cl domain, the diacylglycerol sensor described above. In fact, their ability to recruit PKC to membranes is so effective that phorbol esters cause maximal activation of conventional PKCs, bypassing the requirement for Ca2+. This module is found in a number of other proteins in addition to PKC, so the profound effects of phorbol esters on cells are mediated by other proteins in addition to PKC. 

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