Author Archives: MeganWolf

The Yew Tree: From Foe to Friend

For thousands of years, people have used the poisonous materials from the yew tree to fight their battles. Ancient people used the extract from the bark to coat the tips of their war arrows, rendering them deadly. The Romans used the same substance to assassinate political leaders. In the modern era, the yew tree is fighting a new opponent: cancer. A chemical, Taxol, which is derived from the plant is one of the most prevalent chemotherapeutic agents used today to battle cancer.

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The poisonous properties of the yew have been known for thousands of years Source: Wikimedia Commons

Taxol, or paclitaxel, is toxic to cells because it disrupts the mitosis process. Mitosis is when a cell splits into two identical daughter cells. It is essential to maintain an healthy and growing organism. When the yew plant is ingested, cells cannot divide because of the these anti-mitotic properties of paclitaxol. Division halts and the cells die, which can eventually result in the death of the whole organism. These anti-mitotic properties are why Taxol works as an agent against cancer. This is because cancerous cells have mutated so that they divide uncontrollably. As Taxol disturbs cell division, it can efficiently kill certain types of cancerous cells such as breast and ovarian cancer.

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The Yew Tree                                                           Source: Wikimedia Commons

The yew tree still holds some secrets: unlike many drugs originally derived from plant sources, there is no entirely synthetic pathway that reproduces the naturally derived compound. That is to say, for this chemotherapy to have full effect, it still needs materials acquired from yew trees. As the National Cancer Institute reports, a manufacturing technique has been developed recently which combines synthetic compounds and the chemicals from the yew bark. This has made the drug more accessible and affordable, but Taxol currently used in cancer treatment is still plant-based.

With a chemotherapeutic drug like Taxol, doctors scientists use the same properties of the substance that has been killing us for thousands of years to kill the enemy within us: cancer.

How Taxol Works (Source: Cancer quest)

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-Megan Wolf

DNA Evidence – Not so airtight after all

March 2009. Police departments across Europe have been searching for a serial killer known as the Phantom of Heilbronn. Her DNA had been found at crime scenes all over the subcontinent. Other than the DNA, police had no other clues to her identity. Finally, a break, but not exactly what authorities were looking for. They had found an individual with matching DNA, only it was a man. Stumped as to how their profile was matching to a man – a genetic impossibility – investigators re-examined the evidence. They eventually determined that the Phantom of Heilbronn was just that, a phantom. The DNA belonged to a worker in the factory that manufactured the cotton swabs used by the forensic officers. The swabs had contained minor contamination from the worker, but had been used to collect samples at crime scenes. When analyzing the swabs, investigators found the DNA profile of the worker, instead of that of the culprit.

Every cell with a nucleus contains molecules of DNA, which function as the blueprint of life. Cells read the code in DNA and use it to construct and operate the body of the organism. Humans share 99.9% of their DNA sequence, but there is variation in the code. Modern technology can read an entire DNA sequence and isolate the parts in which there is known to be variation, known as loci. The variation at all loci produces a DNA profile that is as unique to an individual as a fingerprint. Forensic analysts working with police departments then use this to match a suspect’s DNA to that found as evidence at a crime scene.

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How DNA analysis works. Source: The National Forensic Science Technology Center (NFSTC)

Media and popular culture would have you believe that DNA fingerprinting technology is infallible. As the case of the Phantom demonstrates, it most certainly is not. Since with modern technology DNA can be extracted from only a few cells, post-crime contamination during crime scene handling is becoming increasingly problematic. Cells from anywhere or anyone can end up on pieces of vital evidence and be misidentified as the cells of the criminal. Sometimes, as in the case of the phantom, this wastes valuable time and resources. Other times, such as in the controversial Amanda Knox case, it can land the wrong person in jail.

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Crime scenes are at high risk of DNA contamination  Source: Wikimedia commons, By Tex Texin from Blogosphere, Cyberspace – “Crime Scene Do Not Cross” tape, CC BY 2.0

Crime scene contamination, along with other ways DNA evidence can be corrupted, cast doubt on the perceived faultless technique of DNA fingerprinting. Sometimes, even if with a DNA match cannot prove guilt beyond a reasonable doubt.

Megan Wolf

Rio’s Emerald Pools: A Scientific Whodunit

This summer, when I tuned in to the Rio de Janeiro Olympic games and saw cloudy green waters in the diving pools, I barely batted an eye. I thought this was merely a media stunt. The Brazilian authorities had harmlessly dyed the waters green because it fit with the country’s theme. They have a green flag, they have incredible natural greenery and so on. I soon learned that this was no dye. The waters had, seemingly spontaneously, turned green overnight.

The games’ organizers pointed the finger at an unnamed stadium worker who apparently poured copious amounts of hydrogen peroxide into the pool. Possibly this was an attempt to “super-sterilize” the pool, akin to using peroxide on a skinned knee? However, like most swimming pools, this one had already been treated with chlorine. More specifically, sodium hypochlorite (NaOCl). When NaOCl is combined with water it forms hypochlorous acid, a potent antimicrobial agent. Adding hydrogen peroxide to the mix would have reacted with the chlorine-containing NaOCl in the pool, producing NaCl, O2 and water. As NaOCl is added to kill microbes such as algae, its absence allowed them to proliferate and fill the pool.

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source: BBC sports

According to a recent article  in the C&En News, this response has been refuted by chemists and biologists alike. It seems impossible (or, in science terms: highly improbable) that the algae could reproduce so quickly to muddy the pool overnight. Some scientists believe it was a chemical reaction resulting from the addition of copper-containing antiseptic chemicals in improper quantities. In the presence of chlorine, copper forms a green complex. This theory even accounts for the smell reported by athletes: hydrogen sulfide, which is a by-product of this reaction.

Solutions

Which solution is THE solution?                                  Image Courtesy: Leiem, Wikimedia Commons

As the Newscripts article reports, we will never know the true solution to this chemistry mystery. All pool water, and potential analytic samples, has long gone down the drain. Nevertheless, chemists will always remember the time when their discipline had its moment in the hot Brazilian sun.

– Megan Wolf