New research suggests that magnetic surfaces may have influenced both the handedness and isotopic composition of early biomolecules—potentially solving two mysteries at once.
The question of how life began on Earth has fascinated scientists for centuries. Among its many puzzles, one stands out as particularly persistent: why do the molecules of life favor one “handedness” over another? Amino acids, the building blocks of proteins, are almost exclusively left-handed in living organisms, while the sugars in DNA and RNA twist to the right. This phenomenon, known as homochirality, has puzzled scientific luminaries from Louis Pasteur to Lord Kelvin.
Now, a surprising new study offers a possible missing link—one that connects not only to molecular handedness but also to another fundamental fingerprint of life: isotope composition. The research suggests that magnetic surfaces may have influenced both properties simultaneously, providing a unified explanation for two of life’s enduring chemical mysteries.
The Mystery of Molecular Handedness
Biomolecules such as amino acids and sugars occur in two mirror-image forms, called enantiomers. In a laboratory setting, chemistry typically produces these forms in equal proportions—a 50:50 mixture known as a racemic mixture. Yet in all living organisms, only one form is ever found.
This asymmetry is not a trivial detail. Biological reactions depend on precise molecular structure; if the chirality is wrong, the reaction may fail entirely. The origins of this preference have remained elusive because both forms have the same chemical stability and do not differ in their physicochemical properties.
The hypothesis that the interplay between electric and magnetic fields could explain the preference for one mirror-image form emerged early on. Nobel laureate Pierre Curie was among those who speculated about this connection. However, it was only in recent years that the first indirect evidence emerged that these force fields can indeed “distinguish” between the two mirror images of a molecule.
The CISS Effect: Connecting Spin and Chirality
The key to understanding this magnetic connection lies in a quantum property of electrons called spin. About two decades ago, researchers discovered a phenomenon now known as the chiral-induced spin selectivity (CISS) effect. This effect establishes a robust coupling between electron spin and molecular chirality: when electrons pass through chiral molecules, their transport efficiency depends on their spin orientation.
For chiral molecules, the electron spin is strongly coupled to the molecular frame—meaning that spin can provide a handle on controlling chemical processes involving chiral compounds. This property has opened new avenues for spin-control in chemistry and biology, where chiral molecules are ubiquitous.
The CISS effect manifests in several ways. For instance, electron transport through a chiral monolayer is spin-dependent, and the preferentially transferred spin state depends on the handedness of the monolayer. Researchers have achieved near-perfect spin filtering at room temperature, demonstrating the robustness of this coupling.
More recently, studies have shown that spin-selective behavior exists for freely diffusing molecules near magnetic surfaces, and even for achiral reagents. This expanding understanding has led scientists to consider whether spin-selective processes near magnetic surfaces could have imposed a chiral bias on prebiotic chemistry.
Magnetic Surfaces as Chiral Agents
Building on these insights, researchers have demonstrated that magnetized surfaces can act as chiral agents. The surfaces of magnetic metals such as iron, cobalt, or nickel allow electric and magnetic fields to be combined in various ways—simply by reversing the direction of magnetization.
In a series of experiments, a team led by Karl-Heinz Ernst at Empa and colleagues at Forschungszentrum Jülich deposited spiral-shaped chiral molecules called heptahelicene onto magnetic cobalt islands in ultrahigh vacuum. Using scanning tunneling microscopy, they counted nearly 800 molecules and discovered a striking pattern: depending on the direction of the magnetic field, one or the other form of the helicene spirals had settled preferentially.
This enantioselective adsorption was not limited to the final binding step. The selection occurred even earlier, during a precursor state in which molecules migrated across the copper surface bound only by weak van der Waals forces. The fact that even these weak forces are influenced by magnetism—specifically by the spin of electrons—was previously unknown.
The researchers also solved another mystery using scanning tunneling microscopy: electron transport through individual helicene molecules depends on the combination of molecular handedness and surface magnetization. Depending on the handedness of the bound molecule, electrons with one spin direction preferentially flow through the molecule, effectively filtering out electrons with the “wrong” spin. This CISS effect was shown to occur in individual molecules, not just ensembles.
A Surprising Discovery: Magnetism and Isotopes
While the connection between magnetic surfaces and chirality was already established, a new study published in the journal Chem has added an unexpected twist. The research began at a family dinner, when Prof. Michal Sharon of the Weizmann Institute of Science and her brother, Prof. Yossi Paltiel of the Hebrew University of Jerusalem, began discussing Paltiel’s work on separating molecules by chirality using magnetic surfaces.
Sharon, a mass spectrometry specialist, proposed using her expertise to analyze the separation process. The collaboration led to an experiment with a surprising result. The researchers used right- and left-handed versions of methionine, an amino acid that typically initiates protein synthesis, and passed a solution containing this amino acid through a paper filter embedded with magnetic particles.
To track the molecules, they incorporated two carbon isotopes—the more common carbon-12 and the heavier carbon-13. The result was unexpected: the magnetic filter appeared to separate methionine not only by chirality but also by isotope composition. Molecules containing the heavier carbon isotope showed a stronger attraction to particles magnetized in one direction over the other, regardless of their handedness.
“We used left-handed methionine molecules that differ only in their isotopic composition,” explained Ofek Vardi, a PhD student in Paltiel’s lab. “Remarkably, the magnetic filter consistently favored one composition over the other in the course of the separation”.
This was the most important and surprising finding of the study, according to Paltiel. The results were published in the journal Chem and represent the first direct experimental connection between spin-dependent interactions and isotopic effects in a chiral amino acid.
Connecting Two Fingerprints of Life
Chirality is not the only chemical signature of life. Living organisms also display subtle but consistent differences in isotope ratios compared to the non-living matter around them. Life tends to prefer lighter isotopes: plants and animals, for example, contain slightly less carbon-13 than the surrounding environment. These small shifts serve as a second fingerprint of life and are widely used to detect traces of ancient biological activity.
The new findings for the first time suggest a link between these two fingerprints—chirality and isotope ratios. If early biochemical reactions occurred on magnetic surfaces, that magnetism may have had a lasting influence on both properties.
The researchers propose that the three-dimensional structure of chiral molecules may amplify interactions between electron spin and nuclear spin, linking magnetic attraction and isotope composition in ways not previously recognized. While isotopes can differ in nuclear spin, the effect is usually much weaker—but in chiral molecules, this effect may be amplified.
“The differences between isotopes are tiny, but they can have measurable effects,” the researchers note. Carbon isotopes differ by just one neutron, yet the isotope ratios between living and non-living matter often differ by less than 0.1 percent—and scientists can use these subtle differences to detect life.
A Prebiotic Scenario: Magnetite Lakes
These findings fit into a broader hypothesis about where life might have begun. The group of Prof. Dimitar Sasselov from Harvard University has proposed that life on Earth emerged on natural magnetic surfaces, such as the beds of ancient, mineral-rich lakes.
In these environments, reactions involving iron minerals could have produced magnetized sediments in warm, shallow waters—conditions potentially conducive to life’s beginnings. Over time, these magnetic lakebeds might have favored molecules of one chirality, while also affecting their isotope composition.
The CISS effect provides the mechanism for this symmetry breaking. Magnetic surfaces can act as chiral agents due to the CISS effect, serving as templates for enantioselective crystallization of chiral molecules. Researchers have demonstrated spin-selective crystallization of ribo-aminooxazoline (RAO), an RNA precursor, on magnetite surfaces, achieving an enantiomeric excess of about 60 percent.
This process combines two necessary features for achieving homochirality: chiral symmetry-breaking induced by the magnetic surface and self-amplification by crystallization. The result demonstrates a prebiotically plausible way of achieving homochirality from completely racemic starting materials.
“If life really began on magnetic surfaces, our results provide experimental evidence that magnetism could have been responsible both for the asymmetry of biological molecules and for the isotope ratios in living matter,” Paltiel said.
Broader Implications and Future Directions
The discovery of spin-dependent isotopic fractionation could have implications beyond the origin of life. It may enable new technologies that combine magnetic effects with mass spectrometry to separate both chiral molecules and isotopes. This could have practical applications in the manufacture of drugs, pesticides, and other bioactive chemicals that must be produced with the correct handedness to be effective.
The findings also suggest that isotopic fractionation in biomolecules—often used as a fingerprint of biosynthetic origin—may partly arise from spin-dependent interactions rather than purely thermodynamic or kinetic effects. Even subtle quantum properties such as electron spin can measurably influence chemical outcomes when coupled with molecular chirality and magnetic fields.
Researchers are continuing to explore these connections. A recent study in The Journal of Physical Chemistry Letters demonstrated that reactions of radical pairs with spin-polarized electrons can be enantioselective, providing a quantum mechanism for nature’s emergent homochirality. This theory provides useful bounds on the maximum enantiomeric excess for these reactions and offers an alternative mechanistic basis for how spin-polarized electrons could have initiated chiral symmetry breaking.
Meanwhile, astrophysicists are exploring whether similar mechanisms could operate in space. A study published in The Astrophysical Journal suggests that spin-polarized electrons from magnetically aligned dust grains in protostellar environments could cause chiral asymmetry in prebiotic molecules formed in ice mantles. This raises the intriguing possibility that the seeds of homochirality might have been sown before Earth even formed.
A Missing Link?
The discovery that magnetic surfaces can influence both chirality and isotope composition offers a possible missing link in our understanding of life’s origins. It connects two fundamental chemical signatures of life under a single physical mechanism and provides experimental evidence for a scenario in which magnetism played a central role in the emergence of biological homochirality.
While many questions remain, the research represents a significant step forward. As Ernst acknowledges, his findings alone cannot fully answer the question of the chirality of life—a question that Nobel laureate Vladimir Prelog once described as “one of the first problems of molecular theology”. But the pieces are beginning to fit together.
The experiments show that a magnetic surface can distinguish between mirror-image molecules, that this distinction operates even at the level of individual molecules, and that the effect extends to isotope composition. Together, these findings suggest that the magnetic minerals abundant on the early Earth may have played a more significant role in the origin of life than previously appreciated.
As the researchers concluded in their study: “The present work highlights the correlation between spin-dependent interactions and isotopic effects in biomolecular systems”. By linking magnetic interactions, molecular chirality, and isotope effects, this study establishes a framework for investigating how subtle spin-mediated processes can influence chemical outcomes in complex molecular systems—potentially including those that gave rise to life itself.
By Robert Ritz