Tag: chemistry

Rain clouds: From dust to lawn

Akshat RathiLeave a comment

Clouds turn to rain when water droplets and ice crystals that make them up get too big to resist the pull of Earth’s gravity. This is often caused by particles that disturb the maelstrom of droplets and crystals to become seeds around which cloud matter coalesces. Once this happens, the seeds grow rapidly and eventually fall to the ground.

The seeds can be caused by the passage of exotic things like cosmic rays. More often, though, they are dust particles lofted high into the air. A study in 2009 showed that dust from Taklimakan desert in China, whisked above 5,000 metres, circumnavigated the globe in just 13 days. Because dust needs large horizontal distances to attain sufficient altitude, it might then cause rainfall half-way across the world.

For example, the Rocky Mountains in America push water vapour to higher altitudes that help form clouds. At that point, the theory goes, the clouds run into particles swept in from Africa and Asia. To find if that is indeed what happens Kaitlyn Suski and her colleagues at the University of California, San Diego, examined dust and clouds in Californian skies, to the Rockies’ west. They report their findings in Science.

Ms Suski needed to confirm that dust particles reached heights of about 3,000 metres or more to be able to intercept rain clouds. She also had to verify that they originated in Asia and Africa. She collected samples in an aeroplane equipped with a mass spectrometer, which can accurately determine the dust’s chemical composition. These chemical signatures were then compared with those found in Asian and African deserts. As a cross-check, Ms Suski used data from satellites like CALIPSO, which tracks dust particles’ atmospheric peregrinations.

Perhaps more interesting, Ms Suski also found that rain clouds contained bacteria, though it proved impossible to pin down their origins. Tiny living organisms can float in the atmosphere for a long time, feeding on trace carbon and any other nutrients they bump into. They can also act as cloud seeds.

In 2010 researchers in Norway concluded that bacteria are not as important to rainfall as dust is. But calculations by Ms Suski and her colleagues suggest that their rainmaking powers are amplified when they mingle with desert dust. Deserts may be some of the harshest places on the planet to live, but, if Ms Suski is right, they may be the enablers of life everywhere else.

First published on economist.com.

Reference: Creamean et al. Science 2013. Dust and Biological Aerosols from the Sahara and Asia Influence Precipitation in the Western U.S. http://dx.doi.org/10.1126/science.1227279

Image credit: The Economist

How popular is your element?

Akshat Rathi7 Comments

XKCD inspires many people. Now it has inspired a periodic table geek

XKCD’s latest is a calendar of meaningful dates based upon how often a date is represented in English-language books since 2000. Anders Sandberg, a neuroscientist at Oxford University, has taken inspiration from that calender and his love for yttrium to construct a new kind of periodic table. It’s based on how popular each element is on the interweb (roughly based on Google search hits).

As Anders explains:

Most popular were, perhaps unsurprisingly, gold (2.7 billion) and silver (1.9 billion). Lead got into third place (1.4 billion), perhaps due to the fairly common verb “to lead” rather than its heavy charisma. Why tin is so popular (1.1 billion) beats me.

Least popular are the transuranians, with Bohrium (40,600), Livermorium (106,000) and Flerovium (118,000) as the least popular. These might suffer a bit because they are recently named and people might still remember them with their old names. But they are still fairly obscure outside connoisseurs of heavy nuclei. Why Meitnerium is so popular compared to the others also beats me.

Robert Munafo, an independent American researcher, points out that tin’s popularity might be down to its usage in Vietnamese. Of course, as Anders accepts, his algorithm based on two hours of work isn’t perfect. There may be a way to semantically weed out non-elemental usage of these words, and I do hope that someone starts working on that.

Till then, I take solace in the fact that Osmium seems to be doing just as well as Polonium and Thorium. How is your favourite element doing?

PS: Here is a large PDF/JPG of the table.

The value of medicine

Akshat RathiLeave a comment

Drugs

Drug discovery is a long, arduous and expensive process. Is it worth it?

“One minute I was looking at death. The next, I was looking at my whole life in front of me,” said Suzan McNamara, a patient suffering from chronic myeloid leukaemia (CML), a nasty form of blood cancer. She had just heard that she would be receiving doses of imatinib, a drug that had shown remarkable recovery among patients of this cancer. Four decades of research was needed to make this drug, and to enable such a moment for a cancer patient. It is Ms McNamara’s story and that of many others like her that could possibly justify billions of dollars and years of efforts put into discovering drugs.

CML causes unregulated growth of white blood cells leading to pain, debilitating illness, and, before imatinib was discovered, all too often, death. The only options for treatment, before the drug therapy became common, were a bone marrow transplant, which is very risky, or daily infusions of interferon, an artificial way of boosting a patient’s immune system that has severe side-effects.

The process of discovering a drug like imatinib, commercially known as Gleevec, is a long one. First pharmacologists pick apart the workings of the disease and find a pathway that can be targeted. Then chemists design molecules or use readymade libraries of molecules to block (or, occasionally, activate) that pathway. Typically, of the 5000 molecules that showed promise at this first step, on average, only five are deemed safe enough to undergo human trials. Then, after three to six years of clinical testing, only one of those five molecules may become a drug. Finding a drug is literally like looking for a needle in a haystack. All considered, the success rate is 0.02% and it requires more than a decade worth of research at an average cost of $1 billion.

But imatinib was worth it. It was the first drug that could precisely target cancerous molecules. The science that underpins the achievement began with a discovery in 1960. Two researchers at the University of Pennsylvania found that cancerous cells possessed a particularly small chromosome (number 22 out of the 23 chromosomes that make up human DNA), and this was proposed as the cause of unregulated growth. This was the first time that cancer was linked to a genetic abnormality.

How that abnormality led to cancer remained a mystery until new techniques to visualise segments of this chromosome were found in 1973. Then Janet Rowley, of the University of Chicago, showed that the small size of chromosome 22 was due to an exchange of one of its large segments with a small fragment from chromosome 9. The alien material on chromosome 22 now led to the production of a cancer-causing protein. This rogue protein, an enzyme, was involved in the regulation of cell growth. Dr Rowley postulated that blocking this enzyme should stop cancerous cells.

The charge to find the blocking agent was taken up by medicinal chemist Nicholas Lydon, of Novartis, and oncologist Brian Druker, then of the Dana-Faber Cancer Institute in Boston. They needed to find a molecule that will selectively block the rogue enzyme and leave hundreds of useful ones alone. Following the iterations of the drug discovery process, the team took eight years of efforts to find imatinib. In Phase II clinical trials nearly every patient who took the drug felt surprisingly better in a short period of time, which led to a fast-tracked approval for the molecule from the Food and Drug Administration in 2001.

Imatinib was also approved for treatment of gastrointestinal stromal tumours and other forms of leukaemia, too. Earlier this year, Dr Rowley, Dr Lydon and Dr Druker received the prestigious $650,000 Japan Prize given for outstanding achievements that advance the frontiers of knowledge. “Their work shocked the world of clinical medicine”, the prize citation said. Times have changed drastically from early 20th century when patients depended on good fortune, as drugs were often only found serendipitously.

Ms McNamara was diagnosed with CML in 1998. By the time she received imatinib through a clinical trial in January 2000, her condition had become quite severe. “I was basically on my last limb,” she recalls. Before imatinib was discovered, only three out of five CML patients survived for more than five years after diagnosis. But a 2011 study showed that even eight years after diagnosis, only 1% of CML-related deaths occur among patients using the wonder drug.

With her health restored to normal, Ms McNamara went on to get a PhD in leukaemia research. Quite early in her studies she realised she may not be the one to cure leukaemia herself, but she said, “I might publish one paper that has one key for the next person to go a step further. That’s important”.

Drug discovery is a long, arduous, and expensive endeavour, but it is a process that is being continuously refined to produce results faster and more cheaply. Researchers consider themselves fortunate if they witness the successful launch of a drug in their lifetime, but extraordinary stories of patients motivate them to keep improving this process and searching for that elusive molecule.

Free image from here.