Sarin Gas is now part of the landscape of conflicts around the world. In the ongoing Syrian civil war, the Assad regime has used Sarin gas against civilians–with much of the world demanding the ouster of Bashar al-Assad as a result. U.S. troops return from Middle East conflict with ‘Gulf War Syndrome’ – which some believe to be the result of sarin gas exposure.
Chemists, biologists, and medical scientists are looking for a direct cause-and-effect relationships between Sarin exposures and long-term health effects – and ultimately searching for a vaccine.
Could a Sarin Gas vaccine change the face of modern chemical warfare?
About Sarin Gas
Sarin was invented in 1938 by German chemists who were utilizing processes invented by Fritz Haber, who died in 1934. Haber was a prolific researcher who achieved acclaim for inventing the process of converting nitrogen gas into ammonia. Ammonia was needed for various chemical syntheses employed for medicines and poisons, alike. There was no simple way to make ammonia from nitrogen. However, Haber made use of the cheapest ingredients: nitrogen and hydrogen gases–the eventual process became known as the Haber process.
Sarin gas is odorless and colorless. Brief exposure to Sarin gas can lead to the some of the following symptoms: distinctively poor muscle control in a convulsed state, vision problems–poor and decreased eye sight with possible blindness, frothing at the mouth, and migraines. These symptoms occur within the first 20 minutes. After 20 minutes the symptoms can become permanent or death may occur.
One of the best-documented cases of Sarin exposure occurred in a Japanese subway. In March 1995, a cult group known as AUM Shinrikyo launched a coordinated terrorist act upon innocent civilians. Twelve died and many were permanently harmed from the exposure.
Chemistry of Sarin Exposure
The molecule Sarin is known as an organophosphate. These molecules are Carbon-bearing molecules (organic molecules) that contain phosphorous-oxygen extensions (bonding).
Exposure happens with skin contact or inhalation, and the poison enters the bloodstream. The poison attacks the enzyme known as Acetylcholinesterase, which controls muscle extension and contraction.
After twenty minutes, the organophosphate Sarin induces further changes to the enzyme, bonding irreversibly to it and preventing the Acetylcholine from binding to the Acetylcholinesterase.
The excess Acetylcholine over-stimulates nerve tissue that will eventually produce Parkinson-type symptoms and deadlier symptoms, too.
Chemistry of Acetylcholinesterase and Acetylcholine
The biomolecules, Acetylcholine and Acetylcholinesterase (enzyme) occur in muscle and in the brain stem tissue–the molecule and enzyme are organic chemicals. The pair work together assuring the molecule Choline is bound to the enzyme, Acetylcholinesterase.
The Choline molecule is generated from Acetylcholine–it is cleaved when Choline binds to the enzyme, Acetylcholinesterase.
The reaction is a part of the healthy functioning of muscle and nerve tissue. The enzyme and non-cleaved molecule occur together and are responsible for the healthy functioning of mammalian muscle and nerve tissue.
Treatment of Sarin Exposure
The treatment of Sarin exposure is addressed with a class of chemical compounds known as Oximes. Oximes reverse the early stages of poisoning. While reversal is one answer to the poisoning, a difficult aspect of exposure is treating affected brain tissue. Organophosphates can readily cross the Blood Brain Barrier, but Oximes, as a rule, must be chemically modified so the molecules can easily cross the Blood Brain Barrier.
A plain Oxime (Hydroxyl Amine) is too water-soluble (the molecule possesses water-like physical properties) to possess the ability to cross into the brain, so it is modified with ‘fat-like’ molecular constituents.
Research has shown that substituting carbons for hydrogens in Hydroxyl Amine can lead to oximes being a better mimic of human fats–and allowing penetration through the Blood Brain Barrier.
Preventing Sarin Poisoning
An option pursued by chemists and medical professionals is a vaccine–an approach is to release scavenger molecules into the blood stream. Some of the latest research using scavengers comes from the journal, Chemical Research in Toxicology. Researchers from the Czech Republic and the Scripps Research Institute in California introduced a variation of human Acetylcholinesterase enzyme in a wide-ranging study. The modified human enzyme is introduced with blood plasma that is injected into the bloodstream of mice.
The results showed that organophosphate poisoning can be prevented in animals (as well as computationally and in the test tube). The modified human enzyme acts as a scavenger to remove the organophosphate from the blood stream. The bound organophosphate-enzyme can then be excreted through the kidneys. An eventual human vaccine may come within our lifetimes if further research continues its pace of efficacy.
Sarin was not the poison chosen for this study, however–the researchers used Soman, a related molecule.
The minor differences in molecular structure make Soman more toxic than Sarin.
Both molecules are organophosphates and act against Acetylcholinesterase in the same manner.
Preventing Chemical Warfare
While technology has advanced since the uses of chemical weapons in WWI, we may eventually see that advances in weapons, medicines, food, automobiles, and general life-span will make all weapons of the past seem brutal. Chemistry affords humanity luxuries that seem almost god-like when viewed with the eyes of history.