Molecular beacons developments

Molecular beacons, developed in the mid-1990s, can be delivered into cells with high efficiency, where they are able to detect particular sequences of nucleotides that are indicative of certain types of cancers, thus aiding the early diagnosis of the disease. 

More recently double stranded DNA-binding dyes, (e.g., SYBR Green), have been introduced (Giulietti et al. 2001) which removed the need for an expensive, specific probe to be designed. Other sophisticated tools have been developed to work in conjunction with the Taqman method, for example molecular beacons, scorpions and hybridisation probes. These techniques rely on the FRET (Fluorescence Resonance Energy Transfer) principle but do not require the nuclease activity of the Taq polymerase. The different real-time... 

III) Allele specific hybridisation (Figure 2) Fragments amplified in an allele unspecific PCR are measured with allele specific probes (Molecular Beacons, TaqMan probes or Scorpion), which can either be used in a single PCR or in multiplex reactions for detection of both alleles in one reaction [13]. This method has minor background problems, however the dynamic range may be limited due to competition of the probes. The Molecular Beacon proach has been developed for B. graminis and M. fijiensis [13]. 

There are a few new developments in molecular beacons. Antony et al have studied the effects of various polyamines on the stabilisation of triplexes using a molecular beacon strategy. Using the purine-pyrimidine-rich promoter site sequence of cyclin Dl, an 18-mer G-rich molecular beacon TFO was used, and... 

Molecular recognition is central to biosensor technology. Receptors, enzymes, antibodies, aptamers, molecular beacons, and nucleic acids are mainly used as molecular recognition elements in biosensor development (Chambers etal., 2008). Since 1990, nucleic acids, especially deoxyribonucleic acid (DNA) have been used as biorecognition elements in biosensor technology. These biosensors are named as DNA-based biosensors. 

Molecular beacons are oligonucleotide probes that become fluorescent upon hybridization. We developed a new approach to detect the presence of Salmonella species using these fluorogenic reporter molecules and demonstrated their ability to discriminate between similar E. coli species in real-time PCR assays. A detection limit of 1 CPU per PCR reaction was obtained. The assays were carried out entirely in sealed PCR tubes, enabling fast and direct detection in semiautomated format. 

This study describes the development of a real-time PCR assay employing molecular beacons for detection of Salmonella. This assay combined the speed and specificity of PCR with the specificity and high sensitivity of molecular beacons. A 122 bp region of the himA gene was used as the target (6). The real-time PCR assay is highly specific and a detection limit of one single cell was achieved. 

Several proprietary fluorescence dye-based detection systems that characterize and quantify probe-bound nucleotide sequences have been developed and commercialized in recent years. For example, general and nonspecific DNA dyes can be used that bind with any double-stranded DNA (i.e., the probe-strand complex or otherwise) and are useful in gel electrophoresis. Much more sophisticated systems rely on oligonucleotide probes that incorporate fluorescent dyes that illuminate when a match between complementary strands are made. Included among the latter are TaqMan , molecular beacons, and Scorpion probes. 

Single-strand nucleic acid with a hairpin structure has also been used as a biological element to develop DNA biosensors. The hairpin structure, often referred to as molecular beacon, is labeled with a fluorophore at one end and a quencher at the other end. The hairpin structure brings the labels into close proximity and causes fluorescence... 

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