Displacement amplification

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... 

Walker, G. T., et al. (1992). Strand displacement amplification—an isothermal, in vitro DNA amplification technique. Nucleic Acids Res. 20, 1691-1696. 

Thompson, M. D., Bowen, R. A., Wong, B. Y., et al. (2005) Whole genome amplification of buccal cell DNA genotyping concordance before and after multiple displacement amplification. Clin. Chem. Lab. Med. 43, 157-162. 

HCV and HIV-1). The bDNA assay is being much employed for the quantification of messenger RNA. Moreover, for the detection of viral and pathogenic disorders based on alkahne-phosphatase-sensitive dioxetanes, several assay methods are available these include the Polymerase-Chain-Reaction (PCR) amphfication, probe ligation, strand-displacement amplification and the ligase chain reaction. ... 

Fig. 3. The use of microdissected material increased the sensitivity of the SNP array to LOH in tumor tissues. Regions with LOH are highlighted in black color. B, DNA extracted from bulk tumor tissue without microdissection M, DNA was extracted from microdissected tumor cells and amplified by the multiple displacement amplification method (52).

Pressure-driven liquid flow can also be achieved by a piezoelectric actuator and a pivoted lever for linear displacement amplification (nine-fold) on a PMM A chip. Flow rate of 1 nL/min has been attained [380]. 

In another report, the DNA amplification was based on strand displacement amplification (SDA). This method worked at an isothermal temperature of 50°C for the 106-bp product from Mycobacterium tuberculosis [942]. 

Strand displacement amplification (SDA) Target Hindi DNA polymerase I (exonuclease deficient) No... 

Another isothermal amplification technique is strand displacement amplification (SDA). " After heat denaturation of DNA in the presence of four primers, dCTP, dGTP dUTP, and a modified deoxynucleotide (dATPaS), two enzymes are added, an exonuclease-deficient polymerase and a restriction enzyme. The two flanking primers that enter into exponential amplification have a restriction site added to their 5 end and get nicked by the restriction enzyme, allow-ing displacement of strands that can in turn be primed, extended, and nicked. Deoxy-ATPotS is used so that the restriction sites include a hemiphosphorothioate linkage to allow single-strand nicking, instead of cutting through double strands. 

Instead of specific amplification of one target to improve sensitivity, methods that amplify all genomic DNA or mRNAs are useful when the target is in short supply. For example, multiple-displacement amplification uses exonuclease-resistant random hexamers and a highly pro-cessive polymerase to amplify DNA nonspecificaily. Initial DNA denaturation is not necessary and the reaction proceeds isothermally. Similarly, messenger RNA can be generi-caUy amplified with a poly(T) primer modified with an RNA polymerase promoter. After reverse transcription, second-strand DNA synthesis, and transcription, antisense RNA is produced. Both whole genome and antisense RNA amplification are also useful as nucleic acid purification methods before amplification or detection. 

Bray Ward P, et al. Comprehensive human genome amplification using multiple displacement amplification. Proc Natl Acad Sci U S A 2002 99 5261-6. 

Walker GT, Linn CP, Nadeau JG. DNA detection by strand displacement amplification and fluorescence polarization with signal enhancement using a DNA binding protein. Nucleic Acids Res 1996 24 348-53. 

Whole genome amplification of buccal cell DNA genotyping concordance before and after multiple displacement amplification. Clin Chem Lab Med 43 157-162... 

Another example of a DNA machine that can easily be triggered by the actions of an aptamer is based on the isothermal strand displacement amplification (Weiz-mann et al., 2006b). In this case, a single-stranded DNA track contains three distinct domains domain I for the binding of a primer DNA to start replication domain II, which can, upon dnplex formation, be recognized by a nicking endonuclease (which cuts one strand of a double-stranded structure) and domain... 

Figure 4.8 DNA machine based on strand displacement amplification. The track consists of a primer binding sequence (black, I), a nicking recognition sequence (green, II), and a template for the product DNA (blue, IE). (1) Binding of the primer starts replication of the entire track by a DNA polymerase. (2) The fully replicated duplex is nicked on the newly formed strand by the nicking enzyme, regenerating the primer site...

Figur 4 8 DNA machine based on strand displacement amplification. S66 text for full description.)...

In addition to PCR, there are many other technologies to amplify nucleic acids. For example, ligation-based amplification or ligase chain reaction uses sequence-directed oligonucleotide primers and thermostable DNA ligase to assay point mutations, deletions, or insertions in DNA. Strand-displacement amplification uses the inherent strand-displacement activity of DNA polymerases to conduct DNA amplification at a constant temperature. Transcription-based methods such as nucleic acid sequence-based amplification (NASBA) involve in vitro RNA transcription. NASBA and most other transcription-based... 

More recently, whole genome amplification (WGA), multiple displacement amplification (MDA) and other advanced copying techniques have been evolved [72]. 

The principle structure of the active vibration absorber corresponds approximately to the structure of the passive vibration absorber shown in Fig. 6.9 whereby the passive elastic material between mi and m2 has been replaced by a piezoelectric actuator and a displacement amplification system to increase the achievable displacement of m2. The amplification system is given in this example by elastic joints, similar to those illustrated in Fig. 6.9. 

In piezoelectric transducers with displacement amplification the achieved deflection is increased by constructive means. The stiffness of such a design decreases with the square of the displacement amplification ratio and is therefore much smaller than in the stack design. 

---