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 Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

nachricht The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>