Spin-orbit Coupling Modulation in DNA by Mechanical Deformations

Abstract

We consider molecular straining as a probe to understand the mobility and spin active features of complex molecules. The strength of the spin-orbit interaction relevant to transport in a low dimensional structure depends critically on the relative geometrical arrangement of current-carrying orbitals. Understanding the origin of the enhanced spin-orbit interaction in chiral systems is crucial to be able to control the spin selectivity observed in the experiments, which is a hallmark of the Chiral-Induced Selectivity Effect (CISS). Recent tight-binding orbital models for spin transport in DNA-like molecules, have surmised that the band spin-orbit (SO) coupling arises from the particular angular relations between orbitals of neighboring bases on the helical chain. Such arrangements could be probed by straining the molecule in a conductive probe AFM/Break junction type setup, as was recently reported by Kiran, Cohen and Naaman. Here we report strain-dependent kinetic and SO coupling when a double-strand DNA model is compressed or stretched in two experimentally feasible setups with peculiar deformation properties. We find that the mobility and the SO coupling can be tuned appreciably by strain, and the analytical model bears out the qualitative trends of the experiments.

Mechanical Properties of DNA Hydrogels: Towards Highly Programmable Biomaterials

“…Furthermore, hydration around the DNA strands increases stiffness [125], and salt interactions determine the length-scale of this hydration layer resulting in significant swelling of DNA fibers in the absence of salt [60]. Salts act as counterions to stabilize the negative charge of the DNA backbone and govern hole transfer along dsDNA, while the conformational state is responsible for electronic coupling through π-orbital base stacking [126][127][128][129] This mechano-electronic coupling has been utilized to develop a FRET-based nanosensor for mercury [130] and demonstrated an order of magnitude increase in conductivity for A-form DNA relative to its B-form [131]. An alternative mechanoelectric DNA-based probe was developed for potassium detection based on the conformational transition of DNA into a G-quadruplex [132].…”

Role of Exchange Interactions in the Magnetic Response and Intermolecular Recognition of Chiral Molecules

“…From the theoretical perspective, many studies have been carried out using model Hamiltonian approaches in an attempt to rationalize the CISS effect. − Independently of the specific details, the vast majority of these models establish a connection between the spin selectivity and the presence of spin–orbit interaction related to the helical molecular shape (a different approach has been taken, however, in refs and stressing more the influence of the molecule–metal interface). The computed spin polarizations are in general rather small, unless some type of symmetry breaking is introduced, related to, for example, Büttiker probes, − leakages, or time-reversal symmetry. , Atomistic first-principle based investigations are, on the contrary, still rare. ,, Thus, despite considerable progress in elucidating the origin of the CISS, the problem is still subject to intensive debate.…”

Design Considerations for Oligo(p-phenyleneethynylene) Organic Radicals in Molecular Junctions

“…Interestingly, also molecules without any intrinsic magnetic moment but with a helical structure can display spin-dependent electron transport behavior, a phenomenon which has been named chiral induced spin selectivity − and which is commonly attributed to Rashba-type spin–orbit coupling. This, along with other observations such as anisotropic magnetoresistance ,, and electrode- and metal-center-dependent magnetoresistance, , suggests that spin–orbit coupling, possibly resulting from interactions with the electrodes, may play a role in understanding single-molecule magnetoresistance.…”