Assay homogeneous

The main advantage of a homogeneous immunoassay, compared to a heterogeneous immunoassay, is the absence of a separation step. This translates into a simpler procedure and easier automation. However, homogeneous assays are typically less sensitive and more susceptible to sample interferences which are removed in a separation step. 

Perhaps the earliest reports to app r in the area of ECIA were those of Breyer and Radcliff In their homogeneous assay an aromatic diazonium ion was coupled... 

Proteases are enzymes that break peptide bonds in proteins. As such they lend themselves to a variety of homogeneous assay techniques. Most employ labeling both ends of the substrate with a different tag, and looking for the appearance (disappearance) of the signal generated in the intact substrate (product). As an example, for a fluorescence quench assay, the N-terminal of a peptide is labeled with DNP and the C-terminal with MCA. As such, the peptide is fluorescently silent since the fluorescence from DNP is quenched by absorption by the MCA. Another very popular donor/acceptor pair is EDANS 5-[(2-aminoethyl)amino] naphthalene-1-sulfonic acid and DABCYL 4-(4-dimethylaminophenylazo)benzoic acid) (a sulfonyl derivative (DABSYL) [27], Upon peptide cleavage, the two products diffuse, and due to a lack of proximity, the fluorescence increases. 

Product and services of interest include genomics, proteomics, custom research and services, and instruments, accessories, consumables and software. PerkinElmer proprietary technologies include time-resolved fluorescence which is employed in the sensitive Wallac DELFIA system and Wallac LANCE homogeneous assay system, and fluorescence polarization, [FP]2 , a robust fluorescence-based technique for receptor binding assays that is both fast and easy-to-use. 

Amplified Luminescence Proximity Homogeneous Assay (AlphaS-creen ) technology have been reported [50,51]. With an HTS methodology in hand and orthogonal assays previously developed [47-49], nonpeptide antagonists of methyl lysine binding should appear from diversity screening approaches in the near future. 

Figure 14. Homogeneous assay used with the FlowMetrix systems6...

Therefore, chemiluminescent methods using an acridinium ester-labeled cDNA probe allow the discrimination of a mismatched DNA sequence in a homogeneous assay. 

Homogeneous assays require no separation step in order to observe the ratio between the labelled and unlabelled antigen and the antibody. 

Other successful homogeneous assays have been developed such as the fluorescence polarization technique made available by Abbott Laboratories of North Chicago, USA. This competitive immunoassay technique relies upon the principle... 

AlphaScreen (amplified luminescent proximity homogeneous assay) PerkinElmer Life Sciences Donor beads produce singlet oxygen that induces fluorescence in proximal acceptor beads bead-bead proximity results from engagement of binding partners immobilized on the two bead types... 

Hemmila, I., LANCE homogeneous assay platform for HTS, /. Biomol. Screen., 4, 303,... 

Also with short oligopeptide substrates, homogeneous assay Less sensitive towards compound fluorescence... 

Interference by other thiols (e.g. as enzyme buffer components) Homogeneous assay, commerically available components Heterogeneous assay, very low assay volume possible Heterogeneous assay... 

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