Maltose sensor

Multienzyme Electrodes. Coupling the reactions of two or more immobilized enzymes increases the number of analytes that can be measured. An electro-inactive component can be converted by an enzyme to a substrate that is subsequentiy converted by a second enzyme to form a detectable end product (57). For example, a maltose [69-79-4] sensor uses the enzymes glucoamylase and glucose oxidase, which convert... 

CL emission. The system allows a simple determination of phosphate in 3 min with a linear range of 4.8-160 pM. Owing to its sensitivity, this method could be satisfactorily applied to the analysis of maximum permissible phosphate concentrations in natural waters [42-44], Also, the maltose-phosphorylase, mutar-ose, and glucose oxidase (MP-MUT-GOD) reaction system combined with an ARP-luminol reaction system has been used in a highly sensitive CL-FIA sensor [45], In this system, MP-MUT-GOD is immobilized on A-hydroxysuccinimide beads and packed in a column. A linear range of 10 nM-30 pM and a measuring time of 3 min were provided, yielding a limit of detection of 1.0 pM as well as a satisfactory application in the analysis of river water. 

Medintz IL, Goldman ER, Lassman ME, Mauro JM (2003) A fluorescence resonance energy transfer sensor based on maltose binding protein. Bioconjug Chem 14 909-918... 

Electrochemical transducers work based on either an amperometric, potentio-metric, or conductometric principle. Further, chemically sensitive semiconductors are under development. Commercially available today are sensors for carbohydrates, such as glucose, sucrose, lactose, maltose, galactose, the artificial sweetener NutraSweet, for urea, creatinine, uric acid, lactate, ascorbate, aspirin, alcohol, amino acids and aspartate. The determinations are mainly based on the detection of simple co-substrates and products such as 02, H202, NH3, or C02 [142]. 

Figure 16.25 Semiconductor nanoparticle-based fluorescent sensors (a) Forster resonant energy transfer (FRET) between two nanoparticles induced by analyte, (b) crown ether receptor for potassium ions, and (c) operation principle of maltose fluorescent sensor. (Adapted from Chen et at. [144] and Medintz et at. [146])...

Cleavage of maltose by maltase leads to a fraction of 3-D-glucose which is considerably lower than that present in equilibrium (63%). Consequently, the sensitivity of a maltase-GOD sequence electrode is lower for maltose than for glucose. Such a sensor is being used in a commercial analyzer for a-amylase assay in serum (Osawa et al., 1981), indicating the rate of maltose formation. 

The same reaction has been studied in a flow system coupled with a sensor-reference pair of iodide ion-selective electrodes but with the more efficient peroxidase catalyst substituted for molybdenumfVl) [386]. Maltose and cello-biose interfere while samples containing the more serious ascorbic acid, tyrosine or uric acid interferents require pre-treatment [386]. 

The development of a glucose oxidase-based solid-state electrochemical glucose sensor, i licable to flow through measurements. and of an automated enzyme-based colourimetric system for detecting glucose, maltose and starch on microtiter plates, " have been reported. 

Food and drink sensors. In the food and drink industries, quick and inexpensive analysis to ensure quality is incredibly important, and electrochemical biosensors can be used to meet those needs. As discussed in the previous section, glucose biosensors are the most common of all electrochemical biosensors and they have also been used to evaluate the glucose content of different foods and drinks. This idea has also been expanded to include other sugars, including lactose, maltose, galactose, fructose, lac-tulose, and trehalose. ... 

In this FRET-based biosensor (b) The donor FP and the acceptor FP are fixed to the opposite ends of the MRE. When the analyte binds to the MIEE, the conformation of the sensor protein changes thus placing the donor and acceptor FPs side by side. This increases the FRET efficiency. This is usually used for the detection of glucose, maltose, glutamate, and cyclic nucleotides. 

For consistency the same disaccharides were evaluated here as were used in the evaluation of sensor 135. For the structures of D-glucose, melibiose and maltose, see Scheme 34 and for the structures of D-fructose, lactulose and leucrose, see Scheme 35. The fluorescence titrations of sensors 140( =3)-145( =g) and 146(pyrene) with different saccharides, were carried out in a pH 8.21 aqueous methanolic buffer solution, as described earlier. The fluorescence intensity of 140( =3)-145( =8) and 146(pyrene) (1-0 x 10 mol dm , A,ex=342 nm) increased... 

The relative values obtained for maltose were not illustrated in Figure 35 as the relative values were found to fluctuate significantly. The cause of this lies in the value obtained for the observed stability constant (Kobs) of reference compound 146(pyrene)- As the observed stability constant (Kobs) of compound 146(pyrene) with maltosc was only 5 1 when the relative values were calculated small changes in the observed stability constants (Kobs) were found to manifest large changes in the relative values. Nonetheless, it should be noted that observed stability constants (Kobs) for sensors 140( =3)-145( =g) with... 

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