The Chemistry Behind Stone Age Art

In the Stone Age, chemistry was unknown. However, humans had learned the use of pigments for making pictures and symbols. We can see them in caves around the world. How did they know about these pigments?

Cave Art around the world
The next time you take a vacation, we suggest you visit Bhimbetka. Deep inside Madhya Pradesh, this place has many caves where humans have made many beautiful paintings. Did you know that these paintings are as much as 30,000 years old?

There are caves like Bhimbetka in other parts of the world too. The caves of Lascaux in France are world famous, but tourists are no longer allowed there. Blombos in South Africa, Nyero in Uganda, Mulege in Mexico and Kakadu in Australia are other famous sites, where Stone Age paintings can be seen on the walls of caves.

What made them last so long?
Paintings made with oil or watercolour can fade after a few decades. So what made these rock paintings last?

Most of the painted caves are found either in deserts or deep underground. The air in these caves became very dry over time, and no bacteria or fungi could grow. If they could have grown, they would have released carbon dioxide, which would dissolve in moisture to form carbonic acid. Over time, the carbonic acid would corrode the paintings. In caves that weren’t dry enough, the paintings were not so lucky over, vanishing over time. Examples of this are the cave paintings of the Ajanta Caves, which are located in a dense rain-forest. Even though they are just a few hundred years old, only a few fragments remain, on walls that were once richly painted over.

How were these paintings made?
In those days, sophisticated oil paints or water colours were unknown. However, many Stone Age tribes knew the use of coloured mineral pigments. Today we know that these pigments are made of minerals like barium manganate (blue), haematite (red), gypsum (orange), malachite green or limonite (yellow). These are all oxides. Oxides of iron, known as ochres, were also used to make yellow, red or brown colours.

These minerals are sometimes found in caves (which is why Stone Age art is found only in some caves). To make a pigment, the mineral was crushed into gravel by pounding with a big stone. The gravel was then ground between stones to make a powder. The pigment was then mixed with wet clay, gypsum or lime to make a paste that was ready to paint.

Drinkers Should Keep Bag-in-box Wine Cool

Bag-in-box wines are more likely than their bottled counterparts to develop unpleasant flavors, aromas and colors when stored at warm temperatures, a new study has found. Published in ACS’ Journal of Agricultural and Food Chemistry, it emphasizes the importance of storing these popular, economical vintages at cool temperatures.

Helene Hopfer and colleagues explain that compounds in wine react with oxygen in the air to change the way wine looks, tastes and smells. These reactions speed up with increasing temperature. Many winemakers are moving away from the traditional packaging for wine—glass bottles sealed with a natural cork stopper—and trying synthetic corks, screw caps or wine in a plastic bag inside a cardboard box. The scientists wanted to find out how this transition might affect the taste and aroma of wine under different storage conditions.

Californian Chardonnay was stored in five different wine-packaging configurations at three different temperatures for a period of 3 months to study the combined packaging and temperature effects on the sensory and chemical properties of the wines. A trained descriptive panel evaluated aroma, taste, mouthfeel, and color attributes, and the sensory results were correlated to physical and chemical measurements including volatile compounds, SO2, titratable and volatile acidity, oxygen consumption, and wine color, using partial least squares regression.

In general, increased storage temperatures induced the largest changes in the wines; however, significant packaging–temperature effects were found for some attributes as well. Particularly wines stored in bag-in-boxes at 40 °C showed significant increases in oxidized and vinegar aromas and yellow color. Volatile esters also decreased in these wines, while increased levels of compounds generally associated with age- or heat-affected wine were found including 1,1,6-trimethyl-1,2-dihydronaphthalene and furfuryl ether, consistent with previously reported chemical aging reactions. In summary, storing unoaked Chardonnay in different packages significantly changes the sensory and chemical properties depending on the storage temperature. After a storage period of 3 months, bottle storage with various closures changed the wine in a different way than bag-in-box storage.

Using chemical analysis and a panel of trained tasters, the authors studied how storage at various temperatures affected unoaked California Chardonnay stored for three months in different wine packaging types: natural and synthetic corks, screw caps and two kinds of bag-in-box containers. Storage temperature had the biggest impact on all of the wines. Bag wine stored at 68 and 104 degrees Fahrenheit aged significantly faster than the bottled counterparts, becoming darker and developing vinegar notes. All the wines they tested aged better when stored at 50 degrees F.

New Way to Protect Historic Limestone Buildings

Buildings and statues constructed of limestone can be protected from pollution by applying a thin, single layer of a water-resistant coating.

That’s the word from a University of Iowa researcher and her colleagues from Cardiff University in a paper published in the journal Scientific Reports, from the publishers of Nature. In the study, the researchers report a new way to minimize chemical reactions that cause buildings to deteriorate, according to Vicki Grassian, F. Wendell Miller professor in the UI departments of chemistry and chemical and biochemical engineering.

The coating includes a mixture of fatty acids derived from olive oil and fluorinated substances that increase limestone’s resistance to pollution.

“This paper demonstrates that buildings and statues made out of limestone can be protected from degradation by atmospheric corrosion, such as corrosion due to pollutant molecules and particulate matter in air, by applying a thin, one-layer coating of a hydrophobic coating,” she says. “We showed in particular that the degradation of limestone from reaction with sulfur dioxide and sulfate particles could be minimized with an application of this coating.”

One of the buildings the researchers chose for their study was York Minster, a cathedral located in York, England, and one of the largest structures of its kind in northern Europe. Construction of the current cathedral began in the 1260s, and it was completed and consecrated in 1472.

Grassian says York Minster was a perfect structure to study because its limestone surface has been exposed for decades to acid rain, sulfur dioxide and other pollutants. She notes other historic limestone structures could benefit from the coating, including many in the United States.

She notes other attempts have been made to protect existing stonework in cultural heritage sites; however, those coatings(olive oil and fluorinated substances) block the stone microstructure and prevent the edifice from “breathing,” thus creating mold and salt buildup.

Grassian, along with fellow authors Gayan Rubasinghege and Jonas Baltrusatis of the UI chemistry department, have been studying for years reactions of atmospheric gases with minerals such as limestone. In earlier studies, they have shown through detailed analysis that sulfur dioxide could easily degrade limestone and that this degradation reaction was enhanced in the presence of relative humidity.

How do light sticks work?

If you go on a camping vacation, do pack some light sticks in your kit. They are useful for getting some light without electricity or matches. And they come in lots of colours.

Apart from camping, light sticks are used in many other places. Scuba divers use them to look at corals reefs. They are waterproof, need no electricity or fuel, and do not produce heat. After a hurricane, earthquake or fire, it’s dangerous to switch on a light as there may be short circuits. It’s better to use a light stick then.

They are also very popular as decorations in pubs and discos. Smaller versions of them are used to make crazy jewellery like light earrings, light bracelets, light necklaces, as dancing props, and for making Star Wars type lighted swords.

Glowsticking is a form of dance in which the dancer uses one or more coloured glowsticks. They trace out interesting patterns in the air, like the one in the picture.

So how do they work? Light sticks are based on a simple chemical reaction. The most common reaction is hydrogen peroxide and phenol oxalate ester. The hydrogen peroxide is kept in a thin walled glass tube within the light stick, while the ester is outside it. When you tap or bend the light stick, the glass vial breaks. The peroxide is released into the ester.

First, the peroxide reacts with it to form a peroxyacid ester. This isn’t very stable, so it decomposes further, releasing a lot of energy in the process. This energy is absorbed by a fluorescent dye that is coated on the inner wall of the stick. The dye then releases light. The colour of the light depends on the colour of the dye. Rhodamine B gives a red light, while rubrene gives a yellow light.

Wondered how a firefly gives light as it flies through the evening air? A similar reaction happens in its body. An enzyme called luciferase oxidizes a chemical called luciferin. Light is released during this process. Fireflies use light to tell each other where they are. Female fireflies look like worms, so they are called glowworms. They cannot fly.

Many creatures that live deep in the sea, like squids and anglerfish also produce light. The anglerfish produces light at the tip of a long spine that grows from its head. This light attracts prey which the fish quickly gobbles up!

Why Do We Need Peptides?

You or your families might have been given tamiflu to cure him of a bout of bird-flu, but did you end up with a stomach-ache too? Like tamiflu, many medicines have side-effects. In the future, we may have a new form of medicine called peptides that won’t have any side-effects!

One reason we need new drugs is that medicines are not a natural part of our body. We know how they go right, like we know penicillin kills bacteria, or paracetamol reduces fever. But we’ve got to accept that they don’t work perfectly, yet.

That does not mean all medicines are unsafe. For example, tamiflu prevents viruses from escaping infected cells, so they cannot infect new cells. But if you’ve not eaten properly or took some other medicine, a tablet of Tamiflu might give you a mild stomach-ache. Taken properly, most drugs have no bad effects.

Most of the molecules in our body are proteins, which do things like digesting food and taking oxygen to all cells of the body. Every medicine has its correct target protein. For example, tamiflu blocks the action of a protein, which is made by the flu virus. There is a spot on the protein which is important for the virus to work. Tamiflu goes and sits exactly in that spot, stopping the protein dead in its tracks. However, it doesn’t sit very tightly, and in time gets knocked off. So you have to give more Tamiflu after some time to keep the protein under control.

Glutathione (in picture) is an important peptide found in our bodies. It helps to clean up oxygen radicals, which are produced during normal activities of our body. These radicals can damage cells, causing pain, paralysis or poisoning. In patients who have low glutathione levels due to some illness (like AIDS), giving glutathione from outside can help. However, it gets digested in the stomach, so it can’t be taken as a pill. Instead a peptide called N-acetylcysteine is given as a drug. The body converts this to glutathione.

Another peptide being tested in labs now is DSIP(Deltasleep-inducing peptide). Studies show that it can help people who are trying to get off their addiction to heroin or alcohol. It also helps fight narcolepsy, a condition in which the patient feels very sleepy throughout the day (Although we think giving less homework might have the same effect). And it also helps children recovering from the effects of chemotherapy (which is a way to treat cancer).

There are a lot more peptides being tested against all kinds of diseases, cancer and other disorders. If you choose to become a chemist, we hope you’ll make a peptide medicine that’ll solve a major medical problem!

Waste rubber can be converted into quality products

Pioneering new research is set to upset the standard paradigm of downcycling, and as a result, high-quality new plastics from old plastics will soon be a possibility. This breakthrough is made possible thanks to a new kind of material: an environmentally friendly material mix called EPMT. This research team now hopes to upgrade this waste transformation, and has already entered talks with private enterprises to bring their innovation to commercial fruition.

Every year around the world, up to 22 million tonnes of rubber are processed, and a large portion of these goes into the production of vehicle tires. Once the products reach the end of their useful life, they typically land up in the incinerator. In a best-case scenario, the waste rubber is recycled into secondary products. Ground to powder, the rubber residues can be found, for example, in the floor coverings used at sports arenas and playgrounds, and in doormats. But until now, the appropriate techniques for producing high-quality materials from these recyclables did not exist.

Researchers at the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT in Oberhausen have now succeeded in optimising the recycling of rubber waste materials. They have developed a material that can be processed into high-quality products, like wheel and splashguard covers, handles, knobs and steerable castors.

Their breakthrough has already garnered commercial interest. In the ‘Re-use a Shoe’ project, sports gear maker Nike has been collecting used sneakers for some time. The soles of these old sneakers are recycled under the label ‘Nike Grind’ and are reprocessed as filler material for sports arenas and running track surfaces.

The ‘EPMT compound is an innovative breakthrough in more ways than one. The crushing of rubber waste is more environmentally friendly and resource-efficient than producing new thermoplastic rubber products – an important aspect in view of the rising costs of energy and raw materials. ‘EPMT may contain up to 80 per cent residual rubber; only 20 per cent is made up by the thermoplastics,’ says Wack. EPMT can be easily processed in injection mouldings and extrusion machines, and in turn, these products are themselves recyclable.

Altogether, three basic recipes have been developed that collectively can be processed on the large technical production machines. The researchers are capable of producing 100 kilograms to 350 kilograms of EPMT per hour. Spurred on by this success, Wack and his colleagues have founded Ruhr Compounds GmbH. In addition to the production and the sale of EPMT materials, this Fraunhofer commercial spin-off offers custom-made service packages: ‘We determine which of the customer’s materials can be replaced by EPMT, develop customised recipes and also take into account the settings required at our customers’ industrial facilities,’ says the scientist. 

Darker and heavier bottles can protect the quality of white wine

The research conducted at the National Wine and Grape Industry Centre (NWGIC) at Charles Sturt University (CSU), in collaboration with Dr Daniel Dias at The University of Melbourne, examined the impact of light on the quality of white wine, with the ultimate aim to improve its shelf life.

Lead researcher, Dr Andrew Clark said, “A series of experiments dating back to 2008 have attempted to better understand the impact of light on several white wine components that have previously not been investigated. The components were tartaric acid, which is a major organic acid in wine, and iron, a metal ion found at low concentrations in all wines.

“Although not well understood in wine, these same agents were in fact used as photographic emulsions by the pioneers of photography in the mid-1800s.

“We have shown that a chemical process, known as iron (III) tartrate photochemistry, can adversely affect white wine as it may consume wine preservatives and eventually lead to a brown colour. Ultra-violet light as well as blue and green visible light can induce the photochemical process in white wine.

“Darker coloured wine bottles with a thicker wall of glass were found to offer increased protection from this photochemical process.

“These darker and thicker bottles absorb more light so less reaches the wine wine and the extent of detrimental iron tartrate photochemistry is limited. The darker green and amber coloured bottles were particularly useful to absorb the active wavelengths of incident light.

“Wine is mostly exposed to light after bottling and during storage in retail outlets or in the home. Furthermore, wines designed to be stored for longer periods before being drunk are also more likely to have increased light exposure depending on their conditions of storage.

Further studies into the impact of light exposure on wine are currently being carried out by CSU PhD student Ms Paris Grant-Preece at the NWGIC.

A full NWGIC fact sheet on the study, Iron tartrate as a potential precursor of light-induced oxidative degradation of white wine: studies in a model wine system can be found here.

What’s The Function Of Artificial Leaves?

Did you know that just one-thousandth of the sun’s light that reaches the earth could satisfy all of humanity’s energy nine times over? What if we capture this energy cheaply? Perhaps, artificial leaves are the answer?

Solar energy
Today we have solar cells to make energy. But there are some problems. If it gets cloudy, these cells aren’t much use. Solar cells are also expensive. Also, they do not convert light into electricity very efficiently.
But there is a solar cell that’s been around for two billion years that’s perfect. It is the leaf of a plant!

How natural leaves do it
As you know, leaves are the part of a plant where photosynthesis occurs. In this, the leaf uses light energy to convert carbon dioxide & water into glucose.

Photosynthesis has two parts. One part is where hydrogen ions join carbon dioxide to make glucose molecules. The other part is more important to us. This part takes up energy from sunlight and uses that to split water into hydrogen and oxygen. All this happens in a big complex of proteins and chlorophyll.

Artificial leaves
Scientists have figured a way to make a simple device that works like a leaf. One part of it will capture sunlight, and another part will transfer the energy to a cell which will split water into hydrogen and oxygen, which can be stored in tanks. When we need energy, we can put these gases in a fuel cell, where they react to form water and release electricity.

The trick is to find material that is cheap enough for building millions of such devices. These can then be put in vehicles and power plants. Right now a big search is on for finding materials to do these things.

Finding Cheap Materials
Why not directly use the chlorophyll present in leaves? That’s what a team in North Carolina State University in USA did. They extracted chlorophyll from leaves and trapped it in a transparent jelly(Petrolatum). They put tiny electrodes made of carbon nanotubes in this jelly. When sunlight falls on chlorophyll, it seizes a photon and releases an electron. The electron is carried away by the carbon nanotubes to make electricity.

This electricity can drive a cell in which water is split to form hydrogen and oxygen. For that, another team in Massachusetts Institute of technology, USA have found cheap materials to make a cell. It uses electrodes made of indium and tin oxide, and an electrolyte of cobalt and phosphorus ions. This is able to split water quite efficiently.

If we put these two parts together, we can get a cheap artificial leaf that collects energy from the sun. But it is still sometime to go before we have a small, cheap and portable device that can go into our car. But by the time you’re grown, it might be ready!

What are rare earth metals?

Heard of praseodymium and dysprosium? They sound like tongue twisters, don’t they? They’re a part of our daily lives – right inside our gaming consoles, mobile phones and digital cameras! So let’s see how they affect us.

Rare Earth Minerals
Praseodymium and dysprosium join 15 other elements in a group called ‘rare earth minerals’. They are actually not rare. They are quite widely spread out on the earth’s crust. Here’s a picture of the periodic table with the rare earths marked:

Rare Earths All Around Life
Rare earths are widely used in making electronic devices, like your computers and laptops, mobile phones, digital cameras and portable music players.

Let’s look inside a digital camera. The lens is made from a special glass that has lanthanum or lutetium in it, so that the images have no distortion. The electronic circuit board has many tiny magnets in it, made from neodymium, samarium and many other rare earths. Europium and terbium are what help make the display look so colourful. All of these elements, in just one device!

Combinations of rare earth oxides are also used to make high temperature superconductors, which are used in MRI and maglev trains. And new uses are being discovered every day.

Rare Earth Diplomacy
Few of us can imagine going out today without our mobiles and music players. We can’t imagine a house without an LCD TV or an office without laptops. In the future, we’ll have even more electronic gadgets. That means we need more supplies of rare earths.

However, concentrated ores of these minerals are quite rare. They are often found with thorium, a radioactive element. Because of this, mining and refining these elements is both expensive and dangerous.

Today, 97% of all rare earths are mined in China, from the Gobi desert. This makes countries which have many electronics industries – like Japan, India, Taiwan and South Korea – dependent on imports from China. In recent times, as China develops its own electronics industry, the availability of these minerals to other countries has been reduced.

Today a worldwide search is on for sources of rare earths outside China. India, Brazil, Canada and Australia have reserves, from which thousands of tonnes can be mined. You can see a map of rare earth deposits in India here. Recently our Prime Minister made a big deal with Japan to sell rare earths, and more deals are happening.

As we enter the international year of chemistry, we’re going to hear a lot more of these elements!

From Rotting Mushroom to Drug?

Soft rot diseases cause a great deal of damage in agriculture, and turn fruits, vegetables, and mushrooms to mush. By using imaging mass spectrometry together with genetic and bioinformatic techniques (genome mining), German researchers have now discovered the substance the bacteria use to decompose mushrooms. As the scientists report in the journal Angewandte Chemie, the substance called jagaricin could represent a starting point for the development of new antifungal drugs.

Button mushrooms with soft rot develop typical lesions and are eventually completely disintegrate. The pathogen causing soft rot in cultivated mushrooms has been identified as Janthinobacterium agarididamnosum. A team led by Christian Hertweck at the Leibniz Institute for Natural Product Research and Infection Biology in Jena (Germany) wanted to know which bacterial compound is responsible for this destruction in order to better understand the pathobiology and to find possible protective measures. If the soft rot bacteria produce a substance that attacks mushrooms, it is also conceivable that this substance could be effective against microbial fungi, which cause dangerous infections in humans.

Their challenge was to search for an unknown substance that the bacteria do not produce under standard culture conditions, but only when they attack a mushroom. Hertweck and his co-workers used a method called genome mining. They sequenced the genome of the bacterium and searched it for relevant biosynthesis genes. Using bioinformatic techniques, they made predictions about the structures of the metabolites.

The structure of jagaricin – which is what they called the substance – was fully determined using physical chemical analyses, chemical derivatization, and bioinformatics. The compound is a novel lipopeptide with an unusual structure. Pure jagaricin induces the symptoms of soft rot in mushrooms. The researchers were thus able to demonstrate that jagaricin is involved in the infectious process of the soft rot disease. Degrading enzymes presumably also participate.

The scientists also determined that jagaricin is effective against Candida albicans, Aspergillus fumigatus, and Aspergillus terreus, which cause human fungal infections. Perhaps this substance could be a starting point for the development of a new antifungal drug.