Tag Archives: chemistry

Microplastics No Longer a Micro Issue

You wake up in the morning and then press snooze on your alarm clock one more time before groggily dragging yourself out of bed to the bathroom. Quickly you brush your teeth with your electric toothbrush, then hop in the shower and lather yourself with the bottle of that fancy body wash with the microbeads in it. In the kitchen, you grab the lunch you made from the prepackaged salad mix before heading out the door. Now in your car, you turn some knobs on the dashboard to play some music on your way to work or school. In case you have lost count, you have already encountered half a dozen plastic products and it isn’t even 9 AM yet.

Polymerization of ethylene to form polyethylene
Source: Image © Eugbug

Plastics are the result of taking petrochemical monomers (such as ethylene) and converting them to long chain polymers. This is done through a process called polymerization which is relatively easy and cheap to do. Another process, called photo-oxidation occurs as a result of exposure of these long-chain polymers to UV radiation (from the sun) and oxygen (in the air). Essentially, this process causes plastics to become brittle and in combination with the elements (wind and water abrasion), causes the degraded plastics to break into minuscule pieces. When these pieces are between 0.1 and 1000 μm in size, they are referred to as microplastics.

How microplastics are produced and introduced into the food cycle. Roy Cooper/The National

Due to plastics being such a cheap and omnipresent resource, there has been little incentive to recycle such products, leading to an accumulation of plastic waste in landfills and the world’s oceans. It is tragic to see seawater bodies filled with plastic, but only recently has it come into light that these microplastics are starting to make their way into our own bodies too. While seemingly obvious, microplastics have been reported in seafood, but they are also found in fertilizers and in common food items such as beer, sugar and salt. One study from last year found microplastic particles in 17 salt brands from 8 different countries. Additionally, atmospheric fallout of microplastics has also been reported, so it’s very possible we have already been inhaling and consuming microplastics.

A (a) polyisoprene/polystyrene, (b) polyethylene, and (c) pigment (phthalocyanine) fragment. Image (d) is a nylon-6 filament. Source

So what can be done to mitigate the amount of plastic that is becoming ocean waste and effectively microplastics? Our daily lives and plastic products have become too intertwined to even entertain the thought of completely banning plastics worldwide. Fortunately, there have already been movements to ban especially harmful products such as microbeads found in many skin products. But, some effective steps that everyone can implement into their routines are to reduce the use of single-use plastics such as plastic straws or plastic grocery bags. The issue with single-use or “disposable” plastics is that they are difficult to recycle and thus only contribute to plastic waste. Additionally, choosing products that have less plastic packaging is also a viable way to lessen your plastic consumption. Lastly, whenever possible, recycle your plastic products so your plastic water bottle can become a new plastic water bottle and not the microplastics in our food.

The following video is a collaboration between BBC Earth Lab and Exeter University and shows how microplastics can make it through the food chain and potentially onto our plates.

~Isla

Repurposing electron microscopy as a tool for organic chemists

Many small molecules are crucial to life—not only are they used for life-saving drugs, but they also regulate important biological processes within our bodies. In order to understand these small molecules better, scientists have developed various methods to probe what atoms they are made up of, and how these atoms are connected.

Yet one of the newest and most promising of these methods is not so new at all—in fact, it has been a mainstream tool in the field of structural biology for years.

The imaging resolution of biological molecules before and after cyro-EM. Source: Martin Högbom/The Royal Swedish Academy of Sciences.

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Photoswitchable drugs: the light at the end of the tunnel?

Photoswitchable drugs: the light at the end of the tunnel?

For many developed nations, cancer has become the leading cause of death. Regrettably, the current state of cancer treatment still rests heavily on chemotherapy and its toxic side effects. More than ever, our efforts to further develop targeted cancer therapeutics are of paramount importance.

In more recent years, chemists have begun designing light-activated molecules that can be activated upon contact with its target tumor cell and deactivated following cell death.  That said, photoswitchable drugs are not a novel concept; in fact, scientists have been considering synthetic light-switching molecules as promising treatments for blindness, diabetes, Alzheimer’s disease, and antibiotic resistance, to name a few.

Previously, treatments for skin cancer relied on photodynamic therapy (PDT), a process during which patients receive dyes that convert oxygen molecules into their toxic singlet forms capable of killing diseased cells upon activation by light. Given its requirement of oxygen in the body’s tissues, the applicability and potency of PDT are limited by hypoxic tumor environments in which cancerous cells survive without oxygen.

Comparison of (a) classic chemotherapy and (b,c) photopharmacological chemotherapy DOI:10.1002/chem.201502809

Dr. Phoebe Glazer at the University of Kentucky believes that photoswitchable therapies offer a possible strategy for overcoming this restriction. By deriving energy from photons to induce a chemical reaction, photoswitchable therapies enable molecular changes conducive to the recognition and destruction of diseased cells. This approach, unlike current chemotherapy treatments, is capable of killing tumors and saving healthy tissue with specificity, thereby maximizing possible dosage and minimizing dangerous side effects.

Glazer promotes photoactivated chemotherapy drugs that can function as both PDT sensitizers and one-way photoswitches. Using a ruthenium (II) polypyridyl complex, Glazer irreversibly ejected a methylated ligand, and with light, induced the complex to bind to DNA for ultimate cell damage. By modifying the drugs’ ligands, Glazer tuned the molecules’ solubility and the light absorbance wavelength.

ruthenium(II) polypyridyl complexes DOI: 10.1021/ja3009677

Many chemists, including Dr. Wiktor Szymanski at University Medical Center Groningen, are experimenting with molecules that can be switched on and off by light. Once developed, the resulting drugs can be turned on by contact with a targeted cancer cell and turned off after cell destruction. By adding the photoswitchable group, azobenzene, and using UV light to convert the molecule’s configuration, Szymanski produced photoswitchable molecules. 

Photoswitchable molecule developed by Szymanski, Feringa, et al. DOI: 10.1021/jacs.7b09281

Of course, a handful of concerns must be addressed before such “on and off” drugs can become reality. Scientists need to ensure that their switches can work at tolerable wavelengths, specifically ones that can pass through tissue without causing damage. Dr. Achilefu at the Washington University School of Medicine has developed a method called stimulated intercellular light therapy where light is captured by the molecules that target tumor cells. This light has been designed to reach tumor cells beneath the surface of the body (explained in the video below). 

Because of the extreme difficulties and complications related to the synthesis of small molecular drugs, many chemists are skeptical about the approval process of photoswitchable drugs. However, with more research and development, I believe that photoswitchable drugs offer a viable pathway for the future of cancer treatment.

-Brina Kim

 

Record Breaking Temperatures in Superconductive Materials

More than 100 years ago a Dutch scientist named Heike Kamerlingh Onnes at Leiden University discovered a phenomenon in mercury know as superconductivity. When cooled to -269°C the mercury exhibited zero electrical resistance unlike conventional materials that release heat when transporting electricity.

Why is this important if it requires such a cold temperature? Over the past 100 years scientist and engineers have incorporated this phenomenon into our daily lives. This allowed for dramatic advancements in medicine such as the development of the MRI. Our power grid also takes advantage of this weird property. However, only select materials exhibit superconductivity when cooled below a temperature referred to as the critical temperature.

An example of a superconducting radio frequency cavity on display at Fermilab made of Niobium, a common metal in superconductivity applications. Source: Wikimedia Commons

In 1987 the technology was revolutionized when a material called yttrium barium cuprate was found to exhibit superconductivity below -181°C. This temperature is easily reached with liquid nitrogen, a widely accessible coolant. This marvelous material has found itself applied at the Large Hadron Collider in Geneva and most hospitals. While materials with higher critical temperatures have been slowly discovered, recent advancements have been shattering the records.

Timeline of Superconductive Materials
Source: Wikimedia Commons

Among these superconductors are a class which only exist at extremely high pressures. The smelly gas that comes from volcanos and is reminiscent of rotten eggs, Hydrogen sulfide (H2S), is one of these. When cooled to -70°C at 1.5 million atmospheres, hydrogen sulfide exhibits an exotic form of high pressure superconductivity. This discovery in 2015 by Mikhail Eremets and Alexander Drozdov at the Max Plank Institute for Chemistry in Mainz, Germany toppled previous records by 39°C, a significant breakthrough in the search for room temperature superconducting materials. Mikhail Eremets said: “Our research into hydrogen sulfide has however shown that many hydrogen-rich materials can have a high transition temperature.”

This has held true with a recently published paper by the same team in December of 2018. Lanthanum superhydride (LaH10) was found to be superconducting at -23°C, however it was at similar pressures to the previous discovery. This value was found to be even higher at -13°C when pressurized up to 2 million atmospheres as published by scientist at George Washington University in January of 2018. Maddury Somayazuli, an associate professor at The George Washington School of Engineering and Applied Science said: “Room temperature superconductivity has been the proverbial ‘holy grail’ waiting to be found, and achieving it-albeit at 2 million atmospheres-is a paradigm-changing moment in the history of science.” Future experiments are expected to provide more breakthroughs in the field.

An engineer at the Advanced Photon Source, part of Argonne National Laboratory where GW University experiments were preformed. Source: Advanced Photon Source Flicker (CC BY-NC-SA 2.0)

While high pressure superconductors lack application, understanding this  property may allow for the development of new materials. With continued research and the recent breakthroughs, the phenomenon of superconductivity may further be propelled into future technology that will have a significant impact on our quality of life.

-Jonah

References:

1.Drozdov et al, “Superconductivity at 250K in Lanthanum Hydride Under High Pressure,” arXiv:1812.0156 [cond-mat], Dec. 2018.                                        2.Somayazuli et al. (2019). Evidence for Superconductivity above 260K in Lanthanum Superhydride at Megabar Pressures. Physics Review Letters, (122), 027001-6.                                                                                                              3.Researchers Discover New Evidence of Superconductivity at Near Room Temperature. (2019, January 15). Phys.org. Retrieved from https://phys.org/news/2019-01-evidence-superconductivity-room-temperature.html                                                                                      4.Superconductivity: No Resistance at Record Temperatures. (2015, August 18). Max-Planck-Gesellschaft. Retriever from https://www.mpg.de/9366213/superconductivity-hydrogen-sulfide                  5.Eck, J. (2018). The History of Superconductors. Retrieved from http://www.superconductors.org/History.htm

 

 

 

The Awesomeness of Water

Think about one chemical used in daily life. I guess most non-chemists would say water. Water is the basic necessity of all living organisms on Earth. It has a very simple structure: two hydrogen atoms stick with one oxygen atom, but it took the Universe 1.6 billion years to make the first water molecule and 13.6 billion years to make water on Earth!

Have you ever wondered why water is so vital to life? One of the answers is proteins. Proteins are the MVP in the body; they do almost everything in cells and make sure tissues to grow and organs to function. Proteins can fold into complex 3D structures, and their biological reactivity depends on how they fold. Although the mechanism remains unclear, studies indicate that interaction between protein and surrounding water controls protein folding. For example, using a theoretical protein-solvent model and a statistical physics approach, Oliver Collet from Nancy University in France suggests that the hydrogen bonding formed between water and proteins promotes fast protein folding as it is relatively easy to break and reform hydrogen bonds at a high temperature.

Protein before and after folding. Image taken from Wikimedia Commons. https://upload.wikimedia.org/wikipedia/commons/a/a9/Protein_folding.png

In the Catcher in the Rye, the protagonist, Holden Caulfield, wonders what happens to the ducks and fish in Central Park when the large pond freezes. I don’t know about ducks, but I can tell Holden that fish stay at the bottom of the pond and survive over the winter because of the unique thermal properties of water. Hydrogen bonding pushes molecules further apart when water is frozen, so ice is less dense and floats. Oddly, at 4℃, liquid water expands on heating or cooling and has the highest density. This means that water at the bottom is the warmest and maintains a temperature around 4, allowing fish and other aquatic life to survive. In some extreme low-temperature environment, fish use supercooling to avoid freezing. Supercooling is when water is cooled below -40℃ without freezing, and you can even try at home.

How to make supercooled water at home. Video taken from YouTube

Although water is largely used as a solvent in most reactions, it has been found that water can act as an electron donor for certain biocatalytic reactions, enabling more efficient and greener synthetical routes. Avelino Corma, Frank Hollmann and co-workers report water as the electron donor for biocatalytic redox reactions using enzymes, like oxidoreductases. Despite the requirement of additional energy, activation of water as an electron donor is a common natural process: photosynthesis where visible light provides energy to promote water oxidation, generating oxygen along with electrons and protons. Inspired by nature’s method, the researchers come up with a strategy to accelerate water oxidation using photocatalysts, in this case, metal-doped TiO2.

As water is so common in our daily life, it is often underappreciated. It facilitates not only biological activities but chemical reactions and ensures all creatures to survive even under the harshest conditions on Earth

Reference:

Francl, M., Nature Chemistry, 2016, 8, 897-898

Collet, O., J. Chem. Phys, 2011, 132, 085107

Chaplin, M., Water structure and Science, http://www1.lsbu.ac.uk/water/water_anomalies.html#j (accessed Jan. 20, 19)

Supercooling, Wikipedia.org, https://en.wikipedia.org/wiki/Supercooling (access Jan. 20, 19)

Mifsud, M.; Gargiulo, S.; Iborra, S.; Arends, I.W.C.E.; Hollmann, F.; Corma, A., Nature Communications 2014, 5, 3145

 

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A Potential Memory Enhancing Drug

Do you easily forget things? Would you like to improve your memory? A recent study led by Professor Yuji Ikegaya and Dr. Hiroshi Nomura of the University of Tokyo suggests that your long-term memory might be improved with pro-histamine treatment.

The structural formula of histamine. Retrieved from Wikipedia Common.

Pro-histamine drugs increase the level of histamine, which in the central nervous system is associated with learning and memory. Scientists believe that elucidating the role of histamine in memory may help alleviate the symptoms of dementia.

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