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A Turn-On for Catalysts
ScienceNOW ^ | 1 October 2010 | Robert F. Service

Posted on 10/01/2010 4:31:18 PM PDT by neverdem

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Catalysts are prized for their ability to speed chemical reactions by grabbing molecular building blocks and knitting them together. But most catalysts are either on or off—and there hasn't been much scientists could do to flip the switch. Now, however, researchers have created a sandwich-shaped scaffold for turning on and off nearly any catalyst at will. If developed further, the new design could allow researchers to detect minute amounts of a wide range of small molecules—from explosives such as TNT to neurotransmitters that carry messages in the nervous system.

Unlike industrial catalysts, many enzymes—biological catalysts made from proteins—rely on small molecules to turn them on and off. In a process known as allosteric regulation, the binding of a particular small molecule changes the shape of the protein's catalytic site, allowing it to function. A related process can also disrupt a catalyst, turning the enzyme off.

In recent years, several groups have tried to mimic this switching to control synthetic catalysts used in a variety of industrial processes, such as creating plastics and other polymers. Five years ago, Chad Mirkin, a chemist at Northwestern University in Evanston, Illinois, and colleagues created a system that could activate a catalyst that has two metal atoms at its core. Although the scheme worked, only a few catalysts operate with two metal atoms. Moreover, the scaffold can't be easily adapted to work with the much larger number of catalysts that harbor just a single metal atom in their core. So Mirkin and his colleagues wanted to determine whether they could design a new system to work with single-metal catalysts.

They report doing so in today's issue of Science. To make the system work, Mirkin's team designed the catalyst to be like a three-layer sandwich. The "meat" at the center is an aluminum-containing catalyst designed to break open ring shaped compounds and stitch them together into a polymer known as polycaprolactone. When the catalyst is off, two flat organic compounds hide the meat like pieces of bread, preventing the catalyst from interacting with other molecules. But when the researchers add chloride ions, the ions bind at the edges of the outside bread layers, kicking out key nitrogen atoms. The outside layers swing open, allowing the catalyst to do its work. Removing the chloride ions snaps the outside layers shut, and the catalyst is turned off.

Wenbin Lin, a chemist at the University of North Carolina, Chapel Hill, says he's impressed with the work. "It's a very general approach that can be applicable to many different things," Lin says. That could make it useful for detecting a wide variety of small molecules, such as environmental contaminants or compounds present in particular diseases. By triggering the catalyst's production of large amounts of a substance, the method makes it easy to spot when the chosen small molecules are present. The new technique could also prove important industrially to control the work of multiple catalysts that are often used in tandem to build polymers and other complex structures. In cases such as these, researchers would be able to turn catalysts on and off at specific times, ensuring that the production process proceeds in the correct order.

And that's not the end, says Lin. "I think there's likely to be other new [applications] that we do not realize yet."

TOPICS: Culture/Society; News/Current Events; Technical
KEYWORDS: allostericregulation; catalysis; catalysts; chemistry; stringtheory
This is very cool chemistry, IMHO.
1 posted on 10/01/2010 4:31:21 PM PDT by neverdem
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To: neverdem

If I find a catalyst that will convert two methane molecules into a hydrogen molecule and an ethylene molecule, I will be a multi-zillionaire.

2 posted on 10/01/2010 4:52:42 PM PDT by Hoodat ( .For the weapons of our warfare are mighty in God for pulling down strongholds.)
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To: neverdem
Disclaimer: I never took chemistry.

It might be a ridiculous thought but I've been wondering if it's pssible for a catalyst to reverse the chemical reaction that occurs from burning gasoline... put the moslems out of our misery so to speak.

3 posted on 10/01/2010 4:59:20 PM PDT by theymakemesick ( islam - inspired by Satan
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To: El Gato; Ernest_at_the_Beach; Robert A. Cook, PE; lepton; LadyDoc; jb6; tiamat; PGalt; Dianna; ...
A Better Way to Reprogram Cells The second link in the text is the FReebie.

Researchers engineer adult stem cells that do not age

Think saturated fat contributes to heart disease? Think again

Popular Asian spice can cure Alzheimer's disease

FReepmail me if you want on or off my health and science ping list.

4 posted on 10/01/2010 8:04:25 PM PDT by neverdem (Xin loi minh oi)
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To: theymakemesick
Disclaimer: I never took chemistry.

It might be a ridiculous thought but I've been wondering if it's pssible for a catalyst to reverse the chemical reaction that occurs from burning gasoline...

Chemistry was my major. IIRC, inorganic catalysts work in both directions of chemical reactions. That's why the diagram at the top of the article shows arrows pointing in both directions. You may have to enlarge the image to see it. Enzymes, i.e. biological catalysts, probably only work in one direction as the reverse reaction is most likely incompatible with life.

5 posted on 10/01/2010 8:15:51 PM PDT by neverdem (Xin loi minh oi)
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To: AdmSmith; bvw; callisto; ckilmer; dandelion; ganeshpuri89; gobucks; KevinDavis; Las Vegas Dave; ...
Thanks neverdem. Nothing to do with string theory, but possibly a catalyst for discussion.

You must have seen that one coming.

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6 posted on 10/02/2010 7:58:55 AM PDT by SunkenCiv (Democratic Underground... matters are worse, as their latest fund drive has come up short...)
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