Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Why we’re all lefties deep down

06.08.2003


It may be a right-handed world, but recent Purdue University research indicates that the first building blocks of life were lefties – and suggests why, on a molecular level, all living things remain southpaws to this day.


This schematic illustrates Cooks theory of how serine, one of the 20 amino acids that comprise all living things, may have determined the chirality of other biological molecules at the dawn of evolution. "Left-handed" serine, shown here as L-serine, has virtually the same properties as "right-handed" D-serine. But because of an unknown process that possibly caused L-serine to become more prevalent than D-serine in the environment, the strong clusters that L-serine forms bonded only with other left-handed amino acids and right-handed sugars. Other biological molecules with an incompatible chirality were left out of the bonding process, and all the organisms on the planet eventually developed from amino acids with exclusively left-handed chirality.

For higher resolution graphic klick here



In findings that may shed light on the earliest days of evolutionary history, R. Graham Cooks and a team of Purdue chemists have reported experiments that suggest why all 20 of the amino acids that comprise living things exhibit "left-handed chirality," which refers to the direction these basic biological molecules twist–and how a single amino acid might be the reason.

Amino acids can be oriented either to the left or the right and possess the same chemical properties regardless of their chirality. But somewhere along the line, living things evolved using only amino acids of the left-handed variety. Scientists have puzzled over the reason for many years, but Cooks’ group seems to have found the answer: A single amino acid called serine set the standard eons ago, forcing all other biological molecules to follow suit.


"We believe that serine was the first biological molecule to make a chiral choice, possibly one of the root steps in chemical evolution itself," said Cooks, Henry Bohn Hass Distinguished Professor of Analytical Chemistry in Purdue’s School of Science. "Left-handed serine was able to form clusters with strong bonds, and left-handed serine clusters are able to link to other left-handed amino acids. So once serine took the left fork in the road, only the lefties in the primordial soup got to partner up for the dance of life."

Proteins – larger biomolecules – followed the lead taken by serine, Cooks said. The study also suggests that the chirality of other biomolecules, such as sugars, was determined by serine as well.

Cooks’ research, co-authored with Sergio Nanita and Zoltan Takats, doctoral students who are members of Cooks’ research group, appears as the cover article in the current issue of the German journal Angewandte Chemie, considered a leading chemistry publication.

Just as books with thousands of words can be written using only 26 letters, the thousands of proteins that form all living things are built out of different combinations of 20 amino acids, which are among the simplest of biological molecules. All molecules exhibit various chemical properties – reactivity, solubility in water and so forth – but one property that is not as familiar outside chemistry departments is the notion of chirality. Hold a molecule with left-handed chirality up to a mirror, and you see its right-handed sibling, a molecule that generally possesses the same other properties as its lefty variant. But serine, one of the 20 letters in the amino acid "alphabet," is a stickler for chirality in the other molecules with which it associates.

"Most amino acids can form weak bonds with one another regardless of chirality," Cooks said. "Serine is more particular: it forms tightly bound clusters of eight molecules. The clusters, called octamers, are formed of either all right-handed or all left-handed molecules – no mixing allowed."

Though it may seem choosy, serine also is tenacious and loyal in its own way. Once formed, the octamers can form strong bonds with other amino acids of the same chirality. They also can form bonds with sugars that have the opposite chirality: a left-handed serine octamer might bond with several other lefty amino acids and some right-handed sugars as well. This bonding might well have occurred early in a sequence of chemical steps that ultimately led to protein in its many forms.

"We believe that in the primordial soup, left-handed serine was sort of the bouncer at life’s dance club," Cooks said. "If you weren’t a left-handed amino acid, you couldn’t get in to partner up and dance. Because of serine’s ability to form these strong bonds, it essentially forced all other amino acids to twist its way."

The discovery potentially clears up one mystery – where in life’s development the choice between left-handed and right-handed chirality was made. But another mystery still remains: If molecules possess virtually the same properties regardless of chirality, why did left-handed serine become the kingpin molecule? Why didn’t right-handed serine win out?

"We are not sure whether left-handed serine’s dominance in the earliest period of life’s prehistory was arbitrary," Cooks said. "But serine can switch its chirality under mild conditions. If somehow polarized light, for example, or a swirling motion in water were present at a critical moment, some of the right-handed clusters could have become left-handed. This could have cascaded into other prebiotic reactions and set the pace for a billion years of evolution."

Cooks admits that these theories cannot be proven completely, and will concentrate his next efforts on determining whether such conditions could have caused left-handed serine to become dominant. For the moment, he said, he is attracted by the simplicity of the concept.

"There has been a great deal of speculation on how left-handed chirality developed in living organisms, but no agreement about how it happened or how the initial choices were passed on," he said. "The serine theory gives us a simple, coherent picture of one key process – chiral transmission – involved in the origin of life."

This research was funded in part by the National Science Foundation and the U.S. Department of Energy.

Cooks is associated with several research centers located at or affiliated with Purdue, including the Bindley Biosciences Center, the Indiana Instrumentation Institute, Inproteo (formerly the Indiana Proteomics Consortium) and the Center for Sensing Science and Technology.

Writer: Chad Boutin, +1-765 - 494-2081, cboutin@purdue.edu

Source: R. Graham Cooks, +1-765 - 494-5263, cooks@purdue.edu

Chad Boutin | Purdue University
Further information:
http://news.uns.purdue.edu

More articles from Life Sciences:

nachricht Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>