Fusion splice

A fusion splice is a connection in which minimal losses can be obtained. Such a connection is made in a fibre optic splicer (usually controlled by a computer). Two fibres are put into an electric arc where they melt and create a low-loss splice. The splice obtained must be covered with a protective layer in order to prevent the junction from the damage and from the influence by the environment. 

Prefusing—Fusing with a low current to dean the fiber end. Precedes fusion splicing. 

Optical fibers must often be joined, either permanently or temporarily, with minimal coupling loss and back-reflectiom Depending on the performance required, one of three methods are commonly employed to join optical fibers (1) fusion splicing, (2) mechanical splicing, or (3) butt-couphng mechanically aligned fibers terminated with cormectors. The flber ends to be joined must be clean, accurately aligned, and cleaved or polished, so the fiber end-faces are flat and parallel to each other. 

Insertion loss The measured loss in optical power resulting from the scattering of fight at the physical boundary between two optical waveguides (e.g., fibers). The fight scattering is caused by the localized disruption in the refractive properties of the optical path due to the insertion of discrete components such as connectors, mechanical splices, couplers, etc. For fusion splices, this loss is typically referred to as splice loss. ... 

To terminate optical cable in the field, a fiber optic pigtail may be used. A pigtail is typically a single-or multi-fiber cable that has been connectorized at the factory on one end only. The other end remains nonterminated and is spliced to the installed cable. This joint can be either a fusion splice or a mechanical splice. After splicing, the splice point is placed inside a protective splice tray, which is then housed in fiber... 

An even more advanced method of field termination utilizes no-epoxy, no-poKsh connectors. An optical fiber stub is cured into place in the fiber ferrule and polished at the factory. The field fiber is matched up to the fiber stub and a mechanical or fusion splice is made as appropriate inside the connector body. These connectors are typically very quick to install and require few consumables. Although single- and dual-fiber no-epoxy, no-polish connectors are the most common types used, twelve-fiber mechanical splice connectors are also available for use on ribbons. 

Fusion vectors are available that combine a recombinant protein with a mutant mini intein segment (not containing an endonuclease domain) and followed by a chitin binding domain (CBD Zhang et al., 2001). These mutants typically also have an alanine substitution that replaces the cysteine or serine/threonine usually found on the C-extein splice junction. Alanine... 

Figure 2. Genetic aberrations observed in HAT genes, (a) Schematic representation of a balanced chromosomal translocation. These translocations result in the formation two new fusion genes, which can give rise to one or two fusion proteins, (b) Examples of nonsense (RTS patient RT163.1), missense (RT209.1), deletion (followed by frame shift RT231.1) mutations, as well as sphee site acceptor (RT211.3) or splice site donor (RT39.1) mutations...

Figure 4.8 The intein system as used for fusion proteins (Xu, 2000). The fusion proteins undergo self-cleavage at the upstream splice junction. The amino acids that participate directly are shown, and the remainder of the intein and target protein are drawn as boxes. Usually, the intein is conjugated to a chitin-binding domain, so purification of the fusion protein can occur by using a chitin-conjugated column. Self-cleavage can occur overnight.

Chen et al. (2008) have expressed a codon-optimized form of the CM4 peptide in E. coli. In this case, two alternative expression/purification systems were examined namely the widely used glutathione-S-transferase (GST) and a chitin-binding domain (CBD) system with associated intein splicing (New England Biolabs Inc.). The GST system failed to allow recovery of expressed fusion protein. In contrast, the CBD/intein system allowed the recovery of 110 mg/L fusion protein with a final RP-HPLC purification step yielding 2.1 mg/L of pure peptide which displayed antimicrobial activity against E. coli Ki2D3i and Salmonella. 

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