Linked linear amplification

If two PGR primers include elements that cannot be replicated, an exponential expansion is reduced to arithmetic accumulation. However, if multiple nested sets of internal primers (also nonreplicable) are included, product accumulation (at least in theory) can approach that of PCR. This process is known as linked linear amplification. It requires a polymerase, several sets of nested primer pairs, and thermal cycling similar to PCR. ... 

Reyes AA, Ugozzoli LA, Lowery JD, Breneman JW III, Hixson CS, Press RD, Wallace RB. Linked linear amplification a new method for the amplification of DNA. Clin Chem 2001 47 3D40. 

Multi-channel compression systems divide the speech spectrum into several frequency bands, and provide a compression amplifier for each band. The compression may be independent in each of the bands, or the compression control signals and/or gains may be cross-linked. Independent syllabic compression has not been found to offer any consistent advantage over linear amplification [Braida et al., 1979][Lippmann et al., 1981][Walker et al., 1984], One problem in multi-channel compression systems has been the unwanted phase and amplitude interactions that can occur in the filters used for frequency analysis/synthesis [Walker et al., 1984] and which can give unwanted peaks or notches in the system frequency response as the gains change in each channel. 

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.)... 

In vitro transcription is an important technique for the preparation of RNA that can be used for various purposes. At present there are no efficient simple techniques available for the synthesis of RNA oligonucleotides comparable to those of current automated DNA synthesis. In vitro transcription is also the basis for efficient isothermal gene amplification techniques. In vitro transcription can be performed in one of the two formats (Fig. 7.5) by the vector-based approach in which a cloned target (template) DNA is abutted to the T7 promoter in a linearized plasmid (or phagemid) or by the synthetic oligonucleotide-based approach in which the template DNA is linked to a mobile promoter. 

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