Click Chemistry
Source: The Hindu
1.Introduction:
A trio of chemists, Carolyn Bertozzi, Morten Meldal & Barry Sharpless Noble Laureates for "Click Chemistry", in chemistry.
2.Click Chemistry:
- The standard approach of chemists is to mimic nature by making new molecules, which is an art as it is a science.
- In the early 20th century, finding nitrogen in a form usable by plants, was one of the discoveries scientists were striving hard to achieve.
- German Chemist, Fritz Haber cracked the code for ammonia, which combined nitrogen & hydrogen that plants could synthesize for nitrogen and Carl Bosch figured out a way to produce it in massive amounts.
- The Haber-Bosch process is still the dominant way of producing cheap fertilizer & is at the heart of industrialized agriculture.
- This process is extremely energy intensive & polluting. The modern-day challenge is to produce so-called "Green Ammonia".
- This principle extends to most synthetic chemicals where scientists try to create a natural substance which is different from the usual method & often circuitous, creating several unwanted toxic by-products.
- To be able to create new pharmaceuticals, chemists ought to be moving away from trying to make natural molecules & creating new ones in simpler ways.
- For instance, it was hard to coax carbon atoms-the building blocks of organic molecules, from different molecules to link to each other.
- Instead, smaller molecules were taken, which already have a complete carbon frame & link them using bridges of nitrogen/oxygen atoms.
- It may not be as elegantly constructed as the natural stuff but would be efficient, greener & useful.
- This lego-block-like approach to making new molecules is the essence of click chemistry. The 'Click' is from an analogy drawn from seatbelts clicking snugly into buckles.
| Click Chemistry is now used for making biomolecules that can track diseases & corresponding cell processes. Researchers have begun to make clickable antibodies to target a range of tumours. |
- For a chemical reaction to be called click chemistry, it has to occur in the presence of oxygen, and water which is a cheap & environmentally friendly solvent.
- The copper-catalysed azide-alkyne cycloaddition has become synonymous with click chemistry.
- Azides & alkynes are different chemical groups that don't combine naturally but can do so in the presence of copper ions.
- It was discovered that these two had combined to form a third kind of chemical structure called Triazole which is a stable structure found in certain drugs & agricultural chemicals.
- Earlier attempts to make triazoles were inefficient & created undesirable by-products but copper changed the situation.
- Manufacturers can now add a clickable azide to plastic or fibre & modify it to be able to conduct electricity or make them waterproof by adding an alkyne.
3.Bertozzi's Contribution:
- Click chemistry as envisaged by Meldal & Sharpless applies to the non-living world.
- Bertozzi began investigating glycans, which are complex carbohydrates that play an important role in many biological processes like when the immune system is activated.
- Bertozzi wanted to study a particular kind of glycan that attached itself to the lymph nodes but the problem was tracking its presence in the body.
- An alternate way using an azide was found, by attaching a fluorescent molecule onto sialic acid, a constituent of glycans.
- Since copper is toxic to cells, Bertozzi used click chemistry to make a product that avoided it, paving the way for making biomolecules that can be used to track diseases & corresponding cell processes.
4.Afterword:
Researchers have now begun to make clickable antibodies to target a range of tumours. Once the antibodies attach to the tumour, a second molecule that clicks to the antibody is injected which can monitor its growth or deliver a dose of radiation.
