Enantiospeci c biorecognition interactions are key to many biological events. Commonly, bio-a nity values, measured in these processes, are higher than those calculated by available methods. We report here the rst direct measurement of the interaction force between right and left handed helical polyalanine peptides using atomic force microscope (AFM) and calculations based on a simple theoretical model. A force difference of 60pN between same and opposite enantiomer interactions is measured. Additional measurements show spin dependency and fast decay of the interaction term, consistent with spin exchange interactions. This short range enantiospeci c interaction term is especially relevant in crowded biological systems. The results shed light on the importance of spin and exchange interactions in biological processes, providing explanation to the discrepancies between past calculations and experiments. Main TextNature is based on chiral molecules, namely molecules that appear in two forms, enantiomers, that are mirror images of each other. Interestingly, chiral biomolecules, like proteins and sugars appear in Nature mainly as one enantiomer. The origin of "homo chirality" in Nature, was -and is -discussed very intensively in the literature 1 . However, the focus of this work is related to a more fundamental question, i.e., why did Nature preserve chirality so persistently over the many millions years of evolution? In other words, does chirality per se, independent on the speci c handedness, provide properties that serve an important role in Life?The ability of biological molecules to interact selectively with each other is at the heart of all biological processes and the basis of many pharmaceutical concepts. Two important properties -related to chirality -characterize interactions in nature, i.e., very strong enantioselectivity

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Enantiospecific biorecognition interactions are key to many biological events. Commonly, bio-affinity values, measured in these processes, are higher than those calculated by available methods. We report here the first direct measurement of the interaction force between right and left handed helical polyalanine peptides using atomic force microscope (AFM) and calculations based on a simple theoretical model. A force difference of 60pN between same and opposite enantiomer interactions is measured. Additional measurements show spin dependency and fast decay of the interaction term, consistent with spin exchange interactions. This short range enantiospecific interaction term is especially relevant in crowded biological systems. The results shed light on the importance of spin and exchange interactions in biological processes, providing explanation to the discrepancies between past calculations and experiments.

Life is homochiral and homochirality is a fundamental feature of living systems on Earth. While the exact mechanism that led to homochirality is still not fully understood, any realistic scenario on the origins of life needs to address the emergence of homochirality. In order to impose and maintain chirality in a prebiotic network, an environmental factor functioning as a chiral agent is demanded. Magnetized surfaces are prebiotically plausible chiral agents, shown to be effective in enantioseparation of ribose-aminooxazoline (RAO), a ribonucleic acid (RNA) precursor, due to the chiral-induced spin selectivity (CISS) effect. As such, mechanisms for breaking the magnetic symmetry of magnetic minerals are of the utmost importance. Here we report the avalanche magnetization of magnetite (Fe3O4) by the crystallization of enantiopure RAO. The observed breaking of the magnetic symmetry is induced by the chiral molecules due to the CISS effect and spreads out across the magnetic surface like an avalanche, providing a way to uniformly magnetize a magnetic surface without fully covering it. Considered together with our previous results on enantioseparation by crystallization on a magnetic surface, chirality-induced avalanche magnetization paves the way for a cooperative feedback between chiral molecules and magnetic surfaces. With this feedback, a weak natural bias in the net magnetization can be amplified and spin-selective processes can be accommodated on magnetic minerals on a persistent basis.

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