C5b, C6 and C7 complex undergoes a conformational change that exposes hydrophobic regions on the surface of the C7 component capable of inserting into the interior of the microbial membrane.

#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).

#Id: 2562

#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.

#Id: 2564

#Unit 13. Methods in Biology

The loop region of the beacon is designed to bind specifically to a target nucleic acid. Thus, in the presence of the target nucleic acid, the stem region of the beacon becomes separated, releasing the fluorophore from the quencher such that active fluorescence can be observed.

#Id: 2565

#Unit 13. Methods in Biology

Molecular beacons consist of a stem (5–7 bp), and a loop (18–30 base pairs) and are labeled at the 5′ and 3′ ends by fluorophores and quenchers, respectively.