Polymerase chain reaction signal

Quantitative polymerase chain reaction, also called real-time RT-PCR or QPCR, is a method which employs insertion of a signal, such as fluorescence or enzyme activity, into PCR products generated by RT-PCR to determine the amount of messenger RNA (mRNA) in a tissue accurately. 

Both target and signal amplification systems have been successfully employed to detect and quantitate specific nucleic acid sequences in clinical specimens. Polymerase chain reaction (PCR), nucleic acid sequence-based amplification (NASBA), transcription-mediated amplification (TMA), strand displacement amplification (SDA), and ligase chain reaction (LCR) are all examples of enzyme-mediated, target amplification strategies that are capable of producing billions of... 

The advent of the polymerase chain reaction (PCR) was a major turning point in the history of analytical techniques for biomolecules. Since the first publication of the method in 1985, the exponential signal amplification power of PCR was mirrored by an almost similar exponential increase of applications [1-4]. Using a simple and effective signal amplification by repetitive cyclic duplication of a template nucleic acid strand, the signal-enhancing... 

Eig. 5. Several endpoint detection methods were compared for the detection of immuno-polymerase chain reaction (IPCR) amplificate from a direct IPCR (Fig. 3A) of mouse-IgG. Although all IPCR/DNA-detection combinations were able to improve the detection limit of a comparable enzyme-linked immunosorbent assays (ELISA) of approximately 10 amol IgG in a 30-fL sample volume, several differences were observed in actual detection limit, and the linearity of the concentration/signal ratio dependent on the DNA quantification was applied. Best results were obtained for PCR-ELISA (see also Fig. 6) in combination with fluorescence- or chemiluminescence-generating substrates (b, c). With photometric substrates (d) or gel electrophoresis and subsequent spot densitometry (a), a 10-fold decrease in sensitivity was observed. In addition to the more sigmoid curve in gel electrophoresis, an enhanced overall error of 20% compared to 13% in PCR-ELISA was observed for two independent assays. The simple addition of a double-strand sensitive intercalation marker to the PCR-amplificate and measurement in a fluorescence spectrometer further decreased sensitivity (e) and appears therefore to be unsuited for IPCR amplificate quantification. (Figure modified according to references 37 and 65.)... 

The use of nucleotides as tags allowed automated synthesis, cloning and amplification of the coding signal by means of PCR (polymerase chain reaction), and the whole decoding sequence became easy, extremely sensitive and automated. The use of PCR required two oligonucleotide sequences to be... 

It should be noted that the relationship between the final signal output and concentration of the analyte (dose-response) may be one of direct or inverse proportionality, and is dependent on the specific assay format. In addition, a number of different reporter enzymes may be used (e.g., horseradish peroxidase, alkaline phosphatase, p-galactosidase), along with a number of different signaling systems (e.g., substrates that yield chromogenic or fluorescent or chemiluminescent products, activation of signaling enzymes, amplification by biotin-avidin system or polymerase chain reaction). 

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