Recently it was demonstrated that chiral selective chemistry can be induced by spin-polarized electrons from a magnetic substrate. The C-O bond cleavage rate in adsorbed 2-butanol showed a 10% enhancement depending on the chirality of the molecule and spin polarization of the substrate secondary electrons(1). We have recently extended this research to alanine (CH₃CHNH₂COOH), the simplest chiral amino acid. Our initial work examined the x-ray induced photolysis of alanine adsorbed on a thick Permalloy film by monitoring changes in the C1s and N1s photoelectron spectra as a function of irradiation time. Alanine was shown to adsorb in both zwitterionic (~2/3) and neutral (~1/3) forms on Pd(111)(2). C1s and N1s x-ray photoelectron (XP) spectra of alanine adsorbed on Permalloy at 200 K indicate similar adsorption behavior. Irradiation of the adsorbate with x-ray photons results in changes in both the C1s and N1s XPS data, which we attribute to C-C bond fission at the chiral carbon desorbing CO₂ and/or CO from the COO- moiety, and leaving behind ethylamine and/or HCN. Strong support for this assignment comes from similar intensity variations in the C 1s and N 1s XP spectra from D-alanine on Pd(111) as the substrate temperature was increased above room temperature(2). Future work will be devoted to determining if the observed x-ray induced reaction rates are sensitive to the alanine chirality and the polarization of the secondary electrons from the underlying substrate.

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

(1) R. A. Rosenberg et al., Phys. Rev. Lett. 101 (2008) 178301.

(2) Feng Gao et al., Surf. Sci. 601 (2007) 3276.