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 A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>