Piwi-associated RNAs, piRNA, are a special class of miRNA found in germ cells have features distinct from miRNAs.  siRNA (small interfering RNA), which is typically produced during a virus infection.

#Id: 2558

#Unit 13. Methods in Biology

This protein, from the bioluminescent jellyfish  Aequorea victoria, fluoresces with a peak wavelength of 508 nm (green light) when irradiated by ultraviolet or blue light (optimally 400 nm).

#Id: 2559

#Unit 13. Methods in Biology

Cyclization between Ser and Gly is probably rapid, and the oxidation of the Tyr side chain (by O2) is probably the rate-limiting step of fluorophore generation.

#Id: 2560

#Unit 13. Methods in Biology

Genetic engineering has introduced site-specific mutations that enhance fluorescence intensity and shift the wavelength of the emitted light to different colors, thereby making it possible to simultaneously monitor the expression of two or more different genes.

#Id: 2561

#Unit 13. Methods in Biology

An excited fluorescent molecule such as GFP or YFP can dispose of the energy from the absorbed photon in either of two ways: 

by fluorescence, emitting a photon of slightly longer wavelength (lower energy) than the exciting light, or 

by nonradiative fluorescence resonance energy transfer (FRET).

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#Unit 13. Methods in Biology

FRET is inversely proportional to the sixth power of the distance between donor and acceptor. 

#Id: 2563

#Unit 13. Methods in Biology

Molecular beacons are FRET-labelled single-stranded hairpin-shaped oligonucleotide probes originally developed by Tyagi and Kramer in 1996.