Inducing chirality

The basic molecules that make up all living things have a predetermined chirality or ‘handedness’, similar to the way people are right- or left-handed. This chirality has a profound influence on the chemistry and molecular interactions of living organisms. The inception of chirality from the elementary building blocks of matter is one of the great mysteries of the origin of life. Scientists at the US Department of Energy's Argonne National Laboratory have discovered a way to induce this handedness in pre-biological molecules.

"Understanding how the molecules necessary for life originated is one of the most basic scientific questions in biochemistry," Argonne chemist Richard Rosenberg said. "Chirality plays a fundamental role in biological processes and researchers have been trying to discover the mechanisms that led to this property for years."

Rosenberg used X-rays from the Advanced Photon Source to bombard chiral molecules adsorbed on a magnetic substrate and X-ray photoelectron spectroscopy to track changes in the molecular bonds.

He found that changing the magnetisation direction in relation to the high-intensity X-ray beam created an excess of one chirality over another. Changing the magnetisation direction reverses the spin polarisation of the secondary, or low-energy, electrons emitted from the substance.

Iron is a common element and is magnetic in many forms and ionising radiation and magnetic fields are prevalent throughout the universe.

Based on the Argonne results, it is conceivable that chirality could have been introduced by irradiation of molecules as they travelled through the universe while adsorbed on a magnetised substrate in a dust cloud, meteor, comet or on a primitive planet.

"Our study shows that spin-polarised secondary electrons interacting with chiral molecules could produce a significant excess of a given chirality in pre-biological molecules," Rosenberg said.

A paper on Rosenberg's work can be seen in a recent issue of Physical Review Letters.