Tuesday, September 26, 2006

Ozone Depletion (Alison)

It has been known for a long time that the depletion of the ozone layer is accelerated by the use of chlorofluorocarbons, or CFC's. This reaction is cyclical, as it leaves a chlorine radical in the 6th step of halogenation to destroy more ozone molecules. This can be seen in the reaction below:

The reaction begins when UV light strikes a CFC, creating a carbon radical and a chlorine radical. The chlorine radical then collides with an ozone molecule, removes an oxygen atom, and forms chlorine monoxide and an ordinary oxygen molecule. A free oxygen atom then collides with chlorine monoxide, thus creating an oxygen molecule and freeing the chlorine radical to destroy more ozone molecules.

Beyond the obvious environmental effects of this, there are many health effects which have also been documented. The article I read focused on these health effects, mainly skin cancer, cataracts, and immune deficiencies.

Click here for CiteULike reference.

Click here for full-text of article.

Biotinylation (Elizabeth)

Biotinylation is a reaction that is utilized in numerous biochemical experiments and processes. The value of biotinylation lies in the fact that biotin, a B-complex vitamin, forms strong bonds with streptavidin. This biotin-streptavidin complex can then be linked to numerous other biomolecules that function in various applications. Biotin is also readily available (it can be purchased from many different sources) to be used in these applications. The image shown here depicts the biotinylation of spermine, a polyamine that functions in many metabolic processes in eukaryotic cells. Jeon, Kim, Shin et al. utilized this reaction in research that they discussed their paper Differential incorporation of biotinylated polyamines by transglutaminase2 . The biotinylated spermine was used in this experiment to learn more about the intracellular actions of an enzyme, transglutaminase 2. It is believed that this enzyme may cause cell adhesions and apoptosis (cell death). Spermine served as a substrate for transglutaminase 2 so that researchers could better understand how this enzyme functions.

Researchers performed the pictured reaction by combining N, N –di-TFA spermine 2, biotin, 1,3-dicyclohexylcarbodiimide, and 1-hydroxybenzotriazole in anhydrous dimethylformamide (DMF). These substances were combined in a flask and stirred for twenty-four hours at room temperature.

One clinical application of biotinylation is seen in a new wound dressing that was recently created by a German laboratory. This bandage has insulin-like growth factor-1 (IGF-1) attached to the dressing material via biotinylation. The IGF-1 is bound to a biotin-steptavidin-biotin complex, which is connected to amines on the polyurethane gauze. IGF-1 is a hormone, similar in structure to insulin, that stimulates cell growth and reproduction. It is therefore beneficial to use this unique dressing on patients with severe wounds or ulcers, as it will promote healing and epithelial tissue regeneration.