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Chemistry Nobel for trio who make molecules click

Chemistry Nobel for trio who make molecules click


NEW DELHI: Americans Carolyn R Bertozzi and K Barry Sharpless, and Danish scientist Morten Meldal were jointly awarded this year’s Nobel Prize in chemistry for developing a way of “snapping molecules together” — click chemistry — that can be used to map DNA and design drugs that can target diseases more precisely.
Making chemistry more functional
In pharmaceutical research, making complicated molcules can be an expensive and time-intensive process. Building molecules in a lab can require many steps, produce unnecessary by-products, and waste precious materials. Conventional methods can work at smaller scales for testing or clinical trials but become inefficient in large scale manufacturing.
To solve this problem, Karl Barry Sharpless, an American chemist at Scripps Research, developed a minimalistic form of chemistry in which molecular building blocks can quickly and efficiently snap together — he called it “click chemistry”.
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Sharpless, who also won the prize in 2001 and is the fifth person to win twice, found that instead of forcing carbon atoms — the building blocks of organic matter — to bond with each other in the process of building molecules, it’s easier to link smaller molecules with complete carbon frameworks. The central idea is to choose simple reactions between molecules that have a “stronger intrinsic drive” to bond together, resulting in a faster and less wasteful process. Even if click chemistry is unable to perfectly imitate naturally occurring molecules, it can still build modular molecules that serve the same purpose.

At around the same time in the early 2000s, Danish chemist Morten Meldal and Sharpless developed a technique that is now the “crown jewel” of click chemistry — the copper catalysed azidealkyne cycloaddition. While investigating new pharmaceutical materials, Meldal found that adding copper ions to a reaction between an alkyne and an acyl halide unexpectedly created a triazole, a stable ring-shaped chemical structure that’s a common building block in pharmaceuticals, dyes and agricultural chemicals. The alkyne ended up reacting with the wrong end of the acyl halide molecule, creating a chemical group known as azide at the other end. Together, the alkyne and the azide combined to make a triazole.


Until then, researchers had been unable to manufacture triazoles without creating unwanted by-products. But Meldal found that the addition of copper ions helped control the reaction and create just one substance. Sharpless called it the “ideal” click reaction.


Now, when chemists want to combine two different molecules to make a new one, they only need to attach an azide molecule to one and an alkyne molecule to the other, which then snap together in the presence of copper ions. Click chemistry’s applications go far beyond research labs — its industrial potential is immense. Already, click chemistry is used to manufacture new, purpose-built materials.

For instance, adding a clickable azide to a plastic or fibre could allow manufacturers to later “click in” substances that can conduct electricity or fight bacteria.
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Click chemistry can help fight Cancer
While researching glycans, an elusive type of carbohydrate found on the surface of cells that is crucial to the immune system, Stanford University’s Carolyn Bertozzi — the eighth woman to win the prize — found that she did not have the right tools to study them. Bertozzi wanted to attach fluorescent molecules to glycans so they could be easily spotted. She found a way to attach “chemical handles” to glycans for the fluorescent molecules to latch on to. But she needed a “bioorthogonal reaction” in which the handle did not react with any other part of the cell. Bertozzi turned to the same azide used by Sharpless and Meldal to serve as the handle. The azide not only avoids interacting with other parts of the cell, but it’s also safe to introduce in living beings.
As the importance of azides grew with the prominence of click chemistry, Bertozzi realised that her bioorthogonal reaction had more potential. In 2004, she developed an alternate click chemistry reaction that worked without toxic copper, making it safe for living cells.
Bertozzi’s work is already being used to identify glycans on the surface of tumour cells and block their protective mechanisms that can incapacitate immune cells. This method is currently in clinical trials for people with advanced cancer. Researchers have also begun developing “clickable antibodies” that can help track tumours and accurately deliver doses of radiation to cancer cells.


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