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 Newly designed molecule binds nitrogen
23.02.2018 | Julius-Maximilians-Universität Würzburg

nachricht Atomic Design by Water
23.02.2018 | Max-Planck-Institut für Eisenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>