Fluorescence surface-associated

The ligand is hydroxyquinoline-sulfonate (HQS) which forms fluorescent AI-HQS complexes in solution. HQS forms surface complexes with the Al-centers of aluminum oxide surface these surface complexes are also fluorescent. Fluorescence as a function of time during HQS-promoted dissolution of aluminum oxide. Surface-associated fluorescence was calculated from the difference between measured total and dissolved fluorescence. 

From the dependence of the number of bright spots on the rhB concentrations (Fig. 16) we inferred that the observed positions of fluorescent spots were associated with intrinsic sites (pits or bumps) dotted on the Si surfaces. One possible reason for this inference is that an increase in the number of bright fluorescent spots in the 10-7-, 10-6-, and 10-5-M submonolayers involves gradual filling of sites on a Si surface by rhB molecules. Thus, the saturation of the number of bright spots and the appearance of the extra fluorescence not associated with the bright spots from the 10-5- to 10-4-M submonolayers might be due to saturation of the sites and the subsequent spillover of rhB molecules not settled within the sites. 

Chemotaxis was performed using 96-well chemotaxis plates employing 8 p,m filters. Thirty microliters of chemoattractant supplemented with various concentrations of selected experimental agents or vehicle was added to the lower wells of the plate in triplicate. The filter was positioned on top and 25 jxl of cells preincubated with a selected concentration of an experimental agent or vehicle added to the surface of the filter. The plate was incubated 2 hours at 37°C in a humidified C02 incubator, the remaining cells on the surface were removed by adsorption, and the entire plate centrifuged. The filter was then removed and the cells that had migrated to the lower wells were quantified by cell fluorescence of associated calcein-AM. 

In general, the best candidates for in vivo assays are extracellular or cell surface associated enzymes because there are a variety of fluorescent or fluorogenic substrates that can be added to intact cells in natural seawater whose disappearance or products can be measured (e.g., leucine aminopeptidases (LAPs), cell surface amino... 

Fig. 5. Fluorescence pattern of murine fibroblasts after short or prolonged incubation with PrP106-126 coupled to a fluorescent dye. After one hour incubation, the fluorescent peptide is confined to the cell surface (A) while after 24 hours is internalized, the fluorescence being associated with cytoplamic organelles (B).

The droplet detection methods described in this entry include fluorescence, surface-enhanced Raman scattering (SERS), electrochemistry, capacitive, and mass spectrometry. The integration of different detection approaches into the microfluidic droplet device typically involves MEMS and optics technologies. Several methods have been employed to address the integration of detection components with the droplet operation unit however, the task of maintaining overall system functionality remains a challenge. As a result, most of these methods are significantly sophisticated. Trends and issues associated with each detection method are presented. 

Chemiluminescence offers high sensitivity, low background noise, high specificity and reduced instrumental complexity due to the absence of an optical source for excitation, but it is limited in its applicability. This technique has a reduced spatial resolution when compared to fluorescence techniques. Since the light-emitting species are normally not surface-associated, they may diffuse across surfaces and cause emission from different parts. 

Optical biosensors based on fluorescence detection often use the combination of a fluorescent bioreceptor associated with an optical transducer. Fluorescent biosensors may also be obtained by immobilizing whole cells on the surface of a sensor layer. This bioactive layer is usually placed in front of the tip of an optical fibers bundle to generate a fluorescent signal. The optical fibers are required to send the excitation radiation to the fluorescent bioelement and convey the fluorescence radiation up to a fluo-rimeter. In order to improve the simpHcity and reliability of fluorescence-based biosensors, optically translucent supports are used because their optical properties enable detection of fluorescence emitted by the algal cells. 

The presence of metallic surfaces or particles in the vicinity of a fluorophore can dramatically alter the fluorescence emission and absorption properties of the fluorophore. The effect, which is associated with the surface plasmon resonance of the metallic surface, depends on parameters such as metal type, particle size, fluorophore type and fluorophore-particle separation. 

Hochman, J.H., Shimizu, Y., PeMars, R., and Edidin, M. (1988) Specific associations of fluorescent B-2 microglobulin with cell surfaces./. Immunol. 140, 2322-2329. 

Ah initio calculations on the geometry optimization of the 2 kg state of s-traws-butadiene have shown that the C2h planar structure is not stable since it presents several imaginary frequencies associated to out-of-plane vibrations. Three nonplanar structures are found to be stable minima on the potential energy surface. The nonplanarity of this state makes the out-of-plane vibrations effective accepting modes. This fact strongly increases the rate of 2 kg - 1 kg internal conversion, which would explain the lack of fluorescence in butadiene56. 

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