Paper MI+BI-ThA2
Chiral Induced Spin Selectivity in Molecular Bond Dissociation

Thursday, October 25, 2018, 2:40 pm, Room 203A

Since nearly all biological compounds are homochiral, any model of the origin of life must be able to incorporate a mechanism that could lead to preferential chirality. Since chiral molecules have a certain handedness, many researchers have investigated the possible influence of circularly polarized UV photons and longitudinal spin-polarized electrons in creating an enantiomeric excess.[1-3] However, in general the demonstrated effects have been small and/or on the order of the experimental error. Previously we demonstrated [4] that chiral-selective chemistry occurs when X-rays irradiate a chiral molecule bound to a magnetic substrate and suggested that a previously unappreciated source may play a role in chiral-selective chemistry: low-energy (0-20 eV) spin-polarized secondary electrons, produced by photon, electron, or ion irradiation. In the present work, we explore a possible alternative mechanism based on the chiral induced spin selectivity (CISS) effect [5] which suggests that the lifetime of an excited electron in a chiral molecule bound to a magnetic substrate should depend on the magnetization direction of the substrate. To investigate this possibility, we examined the photon-stimulated desorption yield of hydrogen ions from D- and L-Hystidine bound to a magnetized cobalt film. The data indicates differences in the N K edge spectra of the H⁺ ion yield depending on the substrate magnetization direction. These results suggest a possible CISS effect on the excited state lifetime of the dissociative state. Such a mechanism would be applicable to any process that leads to an excited electron in a dissociative state of a chiral molecule bound to a magnetic substrate. Iron is one of the most common elements and many iron compounds are magnetic, so such a mechanism could be applicable in a wide range of prebiotic environments.

The work performed at the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract No. DE-AC02-06CH11357.

REFERENCES

[1] M. Avalos et al., Chem. Rev. 98, 2391 (1998).

[2] W. A. Bonner, Orig. Life Evol. Biosph. 25, 175 (1995).

[3] P. Ehrenfreund et al., Rep. Prog. Phys. 65, 1427 (2002).

[4] R.A. Rosenberg, M. Abu Haija and P.J. Ryan, Phys. Rev. Lett., 101, 178301 (2008).

[5] S. G. Ray, S. S. Daube, G. Leitus, Z. Vager, R. Naaman, Phys. Rev. Lett. 96, 036101 (2006).