April 30, 2026 – A new study reveals that electron spin, a fundamental quantum property, can cause mirror-image molecules to behave differently during dynamic processes, even though they are otherwise identical.

According to the study published by researchers at the Hebrew University of Jerusalem (HU) and published in Science Advances, electron spin, a fundamental quantum property, can cause mirror-image molecules to behave differently during dynamic processes, even though they are otherwise identical.

The researchers found that when electrons move through mirror-image molecules, their spin interacts differently with each form, leading to small but meaningful differences in behavior during dynamic processes like chemical reactions or electron transport. Although these molecules are chemically identical in static conditions, this spin-driven asymmetry could make one version consistently more efficient over time, gradually leading to the dominance of a single “hand” in biology. The findings point to a surprising role for quantum physics in shaping the fundamental structure of life.

Many molecules essential to life exist in two mirror-image forms, known as enantiomers. Chemically, these forms are nearly indistinguishable, yet in living systems, only one version is typically used: amino acids are almost exclusively one type, while sugars follow the opposite pattern. This phenomenon, known as homochirality, has puzzled scientists for more than a century. Existing explanations have struggled to account for why one specific version was selected globally.

The researchers, Prof. Yossi Paltiel of the Center for Nanoscience and Nanotechnology at the Hebrew University of Jerusalem and Prof. Ron Naaman of the Weizmann Institute, suggest that the answer may lie not in the molecules themselves, but in how they behave when electrons move through them. They found that when electrons pass through chiral molecules, their spin interacts with the molecular structure in a way that is not perfectly symmetric between mirror images.

As a result, the two forms can produce different levels of spin polarization, and these differences can influence how efficiently each participates in physical and chemical processes.

This challenges a long-standing assumption that mirror-image molecules should behave identically in magnitude, differing only in sign.

Although the two enantiomers have the same energy, their spin-related properties during motion are not exact mirror images, leading to measurable differences in behavior. Importantly, these differences appear in dynamic processes, such as electron transport and interactions with magnetic environments, rather than in static properties. If one enantiomer consistently interacts more efficiently with its environment under spin-dependent conditions, even small differences could accumulate over time, leading to a global preference.

These findings offer a possible route toward understanding how one molecular “hand” came to dominate in biology. This provides a new perspective on how physical processes, rather than purely chemical ones, may have influenced the earliest stages of biological development.

Looking ahead, the work opens new directions for research at the intersection of physics, chemistry, and biology:

• Exploring how spin-dependent effects influence chemical reactions
• Designing materials that exploit chirality and electron spin
• Investigating how quantum properties shape biological systems

More broadly, the study suggests that symmetry in chemistry may be more subtle and more easily broken than previously thought.

The research, “Dynamic breaking of mirror symmetry in spin-dependent electron transport through chiral media causes enantiomeric excesses,” is published in Science Advances and can be accessed here.

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