Study of enzymatic reaction by electrophoretically mediated microanalysis in a partially filled capillary with indirect or direct detection

2004 ◽  
Vol 25 (2) ◽  
pp. 290-296 ◽  
Author(s):  
Magdaléna Telnarová ◽  
Soňa Vytisková ◽  
Radka Chaloupková ◽  
Zdeněk Glatz
Keyword(s):  
Direct Detection ◽  
Enzymatic Reaction ◽  
Electrophoretically Mediated Microanalysis

scholarly journals Real-Time Interferometric Refractive Index Change Measurement for the Direct Detection of Enzymatic Reactions and the Determination of Enzyme Kinetics

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 539
Author(s):  
Søren Jepsen ◽  
Thomas Jørgensen ◽  
Henrik Sørensen ◽  
Søren Kristensen
Keyword(s):  
Refractive Index ◽  
Enzyme Kinetics ◽  
Adenosine Triphosphate ◽  
Direct Detection ◽  
Enzymatic Reaction ◽  
Refractive Index Change ◽  
Direct Determination ◽  
Initial Reaction ◽  
Enzymatic Reactions

Back scatter interferometry (BSI) is a sensitive method for detecting changes in the bulk refractive index of a solution in a microfluidic system. Here we demonstrate that BSI can be used to directly detect enzymatic reactions and, for the first time, derive kinetic parameters. While many methods in biomedical assays rely on detectable biproducts to produce a signal, direct detection is possible if the substrate or the product exert distinct differences in their specific refractive index so that the total refractive index changes during the enzymatic reaction. In this study, both the conversion of glucose to glucose-6-phosphate, catalyzed by hexokinase, and the conversion of adenosine-triphosphate to adenosine di-phosphate and mono-phosphate, catalyzed by apyrase, were monitored by BSI. When adding hexokinase to glucose solutions containing adenosine-triphosphate, the conversion can be directly followed by BSI, which shows the increasing refractive index and a final plateau corresponding to the particular concentration. From the initial reaction velocities, KM was found to be 0.33 mM using Michaelis–Menten kinetics. The experiments with apyrase indicate that the refractive index also depends on the presence of various ions that must be taken into account when using this technique. This study clearly demonstrates that measuring changes in the refractive index can be used for the direct determination of substrate concentrations and enzyme kinetics.

Detection and Characterization of earth-like Planets

1997 ◽  
Vol 161 ◽  
pp. 299-311 ◽  
Author(s):  
Jean Marie Mariotti ◽  
Alain Léger ◽  
Bertrand Mennesson ◽  
Marc Ollivier
Keyword(s):  
Direct Detection ◽  
Contrast Ratio ◽  
Angular Size ◽  
Physical Nature ◽  
Major Axis ◽  
Infrared Emission ◽  
Space Technology ◽  
Semi Major Axis ◽  
Earth Like Planets ◽  
Visible Wavelengths

AbstractIndirect methods of detection of exo-planets (by radial velocity, astrometry, occultations,...) have revealed recently the first cases of exo-planets, and will in the near future expand our knowledge of these systems. They will provide statistical informations on the dynamical parameters: semi-major axis, eccentricities, inclinations,... But the physical nature of these planets will remain mostly unknown. Only for the larger ones (exo-Jupiters), an estimate of the mass will be accessible. To characterize in more details Earth-like exo-planets, direct detection (i.e., direct observation of photons from the planet) is required. This is a much more challenging observational program. The exo-planets are extremely faint with respect to their star: the contrast ratio is about 10−10at visible wavelengths. Also the angular size of the apparent orbit is small, typically 0.1 second of arc. While the first point calls for observations in the infrared (where the contrast goes up to 10−7) and with a coronograph, the latter implies using an interferometer. Several space projects combining these techniques have been recently proposed. They aim at surveying a few hundreds of nearby single solar-like stars in search for Earth-like planets, and at performing a low resolution spectroscopic analysis of their infrared emission in order to reveal the presence in the atmosphere of the planet of CO H2O and O3. The latter is a good tracer of the presence of oxygen which could be, like on our Earth, released by biological activity. Although extremely ambitious, these projects could be realized using space technology either already available or in development for others missions. They could be built and launched during the first decades on the next century.

A novel enzyme immunoassay for the direct detection of H. pylori antigens in stool

2001 ◽  
Vol 120 (5) ◽  
pp. A492-A493 ◽  
Author(s):  
E HAINDL ◽  
H BENESCH ◽  
A FINCK ◽  
V MUEHISTEIN ◽  
A LEODOLTER ◽  
...  
Keyword(s):  
Enzyme Immunoassay ◽  
Direct Detection ◽  
H Pylori
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