Cold denaturation induces inversion of dipole and spin transfer in chiral peptide monolayers.

Meital Eckshtain-Levi,Soumyajit Sarkar,Yulian Gavrilov,Ron Naaman,Leeor Kronik,Shinto P Mathew,Yossi Paltiel,Yaakov Levy,Sivan Refaely-Abramson,Eyal Capua

doi:10.1038/ncomms10744

Meital Eckshtain-Levi, Soumyajit Sarkar + Show 8 more

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https://doi.org/10.1038/ncomms10744

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Abstract

Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers. Here, we use this spin selectivity to probe the organization of self-assembled α-helix peptide monolayers and examine the relation between structural and spin transfer phenomena. We show that the α-helix structure of oligopeptides based on alanine and aminoisobutyric acid is transformed to a more linear one upon cooling. This process is similar to the known cold denaturation in peptides, but here the self-assembled monolayer plays the role of the solvent. The structural change results in a flip in the direction of the electrical dipole moment of the adsorbed molecules. The dipole flip is accompanied by a concomitant change in the spin that is preferred in electron transfer through the molecules, observed via a new solid-state hybrid organic–inorganic device that is based on the Hall effect, but operates with no external magnetic field or magnetic material.

Highlights

Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers
Experiments performed more than a decade ago showed that the spin selectivity of photoelectrons transmitted through an oligopeptide monolayer is affected by the direction of the dipole moment of the molecules relative to the electrons’ velocity[4] and that both are temperature-dependent[5]
Upon excitation of the nano particles (NPs) (Fig. 6a), an electron is transferred from the substrate to the hole state on the NP (Fig. 6b)

Summary

Introduction

Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers. Experiments performed more than a decade ago showed that the spin selectivity of photoelectrons transmitted (from a gold substrate) through an oligopeptide monolayer is affected by the direction of the dipole moment of the molecules relative to the electrons’ velocity[4] and that both are temperature-dependent[5] We find that the surrounding chemical environment in the SAM can induce ‘denaturation’ upon cooling, much as in biological systems ‘cold denaturation’ can take place due to protein interaction with the surrounding water[13], but here the SAM plays the role of the solvent This dramatic structural change results in a flip in the direction of the dipole moment of the adsorbed molecules, which, in turn, reverses the polarity of the preferred spin in electron transfer experiments. This phenomenon is of importance for the basic understanding of the structure of adsorbed molecules, and opens new possibilities for controlling spin in organic spintronic devices[14]

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