EAGER: Unravel, mimic and control physiology via chiral-induced spin selectivity: a quantum approach

This project aims to unveil and control the “chiral-induced spin selectivity” (CISS) effect at the nanoscale. CISS is an unusual behavior first observed in biological structures, and only later harnessed for technological applications. It describes the fact that, at room temperature, electron transport through molecules with chiral (or mirror) symmetry -- e.g., DNA -- favors particular states of a quantum property called spin.

Such a spin preference effectively translates into more efficient electron transport through chiral molecules than through achiral ones, and this property has justifiably attracted significant interest. Enantiomers (chiral molecules that are mirror images of one another) have opposite electron spin orientation preferences, which could inform drug development; and any technology that relies on optimal charge transport – i.e., the entire electronics industry – could profit from harnessing and controlling CISS-like effects.

CISS might also have tremendous biological implications for signaling, as proteins and most biomolecules are chiral. This research falls within the emergent field of “quantum biology” that studies how the laws of quantum mechanics might play a role in biological function. This work will foment the creation of the first US-based virtual Quantum Biology Center.

Such a center will become a natural organizing structure for quantum biology practitioners to interact, collaborate and disseminate their findings to the broader public. The Center members will demystify and critique potentially dubious claims of quantum effects in biology and place this field on firm scientific ground in the public eye. The Center will also catalyze events such as weekly online meetings on quantum biology, already being organized by the PI for over a year.

The chiral-induced spin selectivity (CISS) describes the fact that, at room temperature, charge transport through chiral molecules favors a particular electronic spin orientation (or ‘spin polarization’). Because of the CISS effect, enantiomers have opposite electron spin orientation preferences. This observation might have tremendous biological implications, as proteins and most biomolecules are chiral.

An unambiguous understanding of CISS at the nanoscale is still lacking. Here the investigators propose to elucidate the mechanisms behind CISS in DNA at the nanoscale. Currently, CISS is studied using chemistry techniques (ex.: electrochemistry, I-V curves) relying on ensembles of chiral nanostructures interacting with electron spins in “classical states”; this precludes, respectively, quantitative measurements of total charge going through the chiral structures and of how spins in “non-trivial quantum states” (e.g., spin superpositions) evolve when transported through such chiral molecules.

The proposed setup – a ESR-STM working with a single chiral molecule that gets injected with electron spins in “non-trivial quantum states” – will overcome the present experimental limitations and thus enable a predictable, quantitative understanding of CISS using the language and tools of quantum mechanics. The investigators will attach DNA under different conditions (e.g., slightly different temperatures, a variety of DNA lengths) to the tip of the ESR-STM and use magnetic resonance techniques to prepare electrons in arbitrary spin states, which will then be injected into the molecule.

By characterizing how the electron coherences are transported through the different nano-chiral potentials, it becomes possible to harness quantum degrees of freedom to hijack and drive both physiology and biological signal processing, and to mimic strategies developed and optimized by nature over millions of years to transduce quantum information.

This project is supported by the Molecular Biophysics Cluster of the Division of Molecular and Cellular Biosciences in Biological Sciences Directorate.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.