radio+labeling

[|Turn ads off - 5/month] Pollution by chlorinated [|chlorinated ethenes] is very common and can pose serious health risks when ground water is contaminated. Vinyl chloride is a carcinogen and can cause cancer of the liver in small doses. It's commonly found from the production of PVC pipes. These pipes are used for plumbing among other common materials. In the study done by Heimann et. al. The authors use [|radio labeling] to see if [|vinyl chloride] (a highly toxic pollutant) can be transformed into ethene by using the co-metabolism of two organisms, Methanosarcina and [|dehalococcoides] Methanosarcina eats acetate to produce [|carbon dioxide] and hydrogen, Dehalococcoides uses this hydrogen to dechlorinate vinyl chloride, making ethene. [|Ethene] is less toxic, but it is flammable in oxygen. It is also used in plant growth and the ripening of fruit. To determine if Dehalococcoides will do this transformation faster if Methanosarcina is providing extra hydrogen the authors radio labeled the acetate.

Radio labeling uses a radio active isotope that is part of a larger molecule A [|radio tracer] is sometimes used in chemistry and biology to track the way an atom moves through a system. For example, In the Heimann study, the researchers wanted to see how much of the radio labeled [|acetate] was converted to hydrogen. To do this they substituted the carbon-12 atom in acetate for an atom of carbon-14. This is commonly done, not just with isotope of carbon, but of other elements as well. Because the atom has the same number of [|protons], it will behave in almost exactly the same way chemically as other atoms in the compound, and with few exceptions will not interfere with the reaction under investigation. The biggest difference comes from the number of [|neutrons] in the atom. This difference allows the labeled molecules to be separated from the regular molecules.

In this study, after 65 days, the researchers were ready to see how much of the acetate [|Sodium Acetate In Action !] - [|The best video clips are right here] had reacted in the system and been transformed into carbon-dioxide. They removed the gas from the reaction vials and stripped it.

Gas stripping is generally done in a tower that has liquid running through it. The liquid then traps the gas. In this study, the gas removed from the reaction vials was stripped in two steps. The first step passed gas through five traps. Two of the traps used the solvent [|2-methoxyethanol] and the last three used [|Carbosorb E], a carbon dioxide absorbing substance. Before performing the second step of the stripping process, all methane left in the remaining fraction was converted to carbon dioxide. This conversion allowed for the carbon dioxide to be absorbed. The second step used only four traps. The first trap used 2-methoxyethanol, the same solvent from the first step. The following three traps used Carbosorb E to trap the remaining carbon.

Finally, the trapped carbon dioxide was measured using a liquid scintillation counter.

A liquid scintillation counter measures ionizing radiation. It has a sensor, called a scintillator, that is a clear crystal made of organic liquids that fluoresce when struck by ionizing radiation. The light coming from the tube is measured using a photomultiplier tube. The tube is attached to an electronic amplifier that can quantify the [|amplitude] of the signal.