A team of scientists has identified a new physical mechanism that could help explain one of the most persistent mysteries in science: why life consistently uses one “handed” version of its molecules and not the other. In a new study led by Prof. Yossi Paltiel of the Center for Nanoscience and Nanotechnology at Hebrew University and Prof. Ron Naaman of the Weizmann Institute, researchers show that electron spin, a fundamental quantum property, can cause mirror-image molecules to behave differently during dynamic processes, even though they are otherwise identical. The work appears in Science Advances.

Many molecules essential to life come 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.