“COLD DENATURATION” INDUCES INVERSION OF DIPOLE AND SPIN TRANSFER IN CHIRAL PEPTIDE MONOLAYERS

Soumyajit Sarkar ¹ Meital Eckshtain-Levi ² Eyal Capua ² Sivan Refaely-Abramson ¹ Yulian Gavrilov ³ Shinto Mathew ² Yossi Paltiel ⁴ Yaakov Levy ³ Leeor Kronik ¹ Ron Naaman ²

¹Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot
²Department of Chemical Physics, Weizmann Institute of Science, Rehovot
³Department of Structural Biology, Weizmann Institute of Science, Rehovot
⁴Department of Applied Physics and Center for Nano Science and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem

Using a combination of several experimental and computational techniques, we show that the α-helix structure of oligopeptides based on alanine and aminoisobutyric acid is transformed to a more linear conformation upon cooling, due to interaction with neighboring molecules in a self-assembled monolayer (SAM) structure. This process is similar to the known “cold denaturation” in peptides, but here the SAM plays the role of the solvent. Our DFT-based first principles calculations show that 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 an associated change in the spin channel that is preferred in electron transfer through the molecules. This is also experimentally 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.