Fluorescence intensity, bound

Fluorescent microvolume assay technology (FMAT ) is a bead-based or cell-based fluorescent technology for homogeneous ELISA-like assays. In FMAT, a laser beam is focused on the bottom of the assay well and the localised fluorescence intensity bound to beads (or cells) is detected as an area of intense fluorescence over the unbound and background fluorescence in solution. Different analytes can be detected with appropriate fluorophores and, by using different sized beads, the assay can be multiplexed to monitor multiple analytes.13... 

The formation of a microphase structure can be sensitively detected by using hydrophobic fluorescent probes. Hydrophobic microdomains tend to solubilize hydrophobic small molecules present together in aqueous solution. For example, diphenylhexatriene (DHT) is hydrophobically bound to the St aggregates in ASt-x in aqueous solution and, as a result, the fluorescence intensity is greatly enhanced. Figure 9 shows the fluorescence intensity of DHT in the presence of ASt-x relative to the intensity in its absence (I/I0) as a function of the ASt-x concentration [29],... 

Kinetic data for total and nonspecific binding are subtracted to give the specific amount bound at the time of antibody addition, and the slow decline in fluorescence intensity thereafter reflects dissociation of bound peptide (also see Ref. 8 for more details). 

Csilibrsition. Quantitative binding analysis requires knowing the concentration of FLPEP, which can be determined for a stock solution of FLPEP by absorption spectroscopy. The quenching by the antibody is essentially quantitative, and the relative amounts of free and bound ligand are calculated from the relative fluorescence intensity. 

Hydrophobic (10a) and hydrophilic (10b) squaraines show a noticeable increase in fluorescence intensity in presence of HSA and importantly dye 10b, containing a sulfo group, exhibits a large intensity increase when bound to avidin, a protein well-known to quench many fluorescent dyes [58]. 

In this paper, to determine the steady state SCP across the transition layer, we analyze the fluorescence intensity decay of dye molecules covalently bound to the polymer chains. The decay is due to the permeation of... 

The ability of some fluorescent dyes to bind DNA quantitatively is exploited in flow cytometry to determine the DNA content of a cell. Dyes such as propidium iodide that bind double-stranded DNA stoichiometrically can be used for the purpose. The intensity of red fluorescence is directly related to the amount of DNA bound by propidium iodide. By comparing the fluorescence intensity of the test specimen and, in turn, its DNA content to the fluorescence intensity of specimens containing normal diploid amounts of DNA, a DNA histogram can be generated. By computing a DNA index, which is the ratio of DNA content of a test specimen to the DNA content of a specimen containing a normal diploid population, information related to the presence of an aneuploid tumor population can be obtained. The DNA index of 1 would imply that the DNA in the test specimen is from a normal diploid population (2N DNA), whereas the DNA index of an aneuploid population will be greater or less than 1. Thus, the DNA index of a tetraploid (4N DNA) would be 2. 

It is important to notice that a change in lifetime is not a necessary result of a change in fluorescence intensity. For instance, the Ca2+ probe Fluo-3 displays a large increase in intensity on binding Ca2+, but there is no change in lifetime. This is because the Ca-free form of the probe is effectively nonfluorescent, and its emission does not contribute to the lifetime measurement. In order to obtain a change in lifetime, the probe must display detectable emission from both the free and cation-bound forms. Then the lifetime reflects the fraction of the probe complexed with cations. Of course, this consideration does not apply to collisional quenching, when the intensity decay of the entire ensemble of fluorophores is decreased by diffusive encounters with the quencher. 

Some biomolecules can induce spectral changes on NIR dyes. The fluorescence intensity of indocyanine green (ICG) increases in intensity when bound to proteins. 35 An increase in the fluorescence intensity signal of a cyanine dye was reported by... 

Self (S4) first proposed the concept of noncompetitive assay for haptens utilizing an adequate combination of an a-type and a jS-type anti-idiotype antibody, in which he used the term, selective antibody for the a-type antibodies. Then, Barnard and Cohen (Bl) applied this assay principle for the determination of serum E2, naming the assay system an idiometric assay. Figure 12A illustrates the assay procedure of the idiometric assay of E2. The target hapten is captured by excess anti-E2 antibody immobilized on microtiter strips by incubation at room temperature for 1 h (step i). After washing the strips, the /3-type anti-idiotype antibody was added in order to saturate (or block) the unoccupied paratope of the anti-E2 antibody (incubation, room temperature for 30 min) (step ii). The a-type anti-idiotype antibody, which has been labeled with a europium chelate (H4), was then added to the plate and incubated at room temperature for a further 2 h (step iii). Finally, fluorescence intensity due to bound europium was measured with a time-resolved fluorometer. Because of large steric hindrance around the bound jS-type antibody (MW 150,000), the labeled a-type antibody would. 

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