Electronic structure study of the bases in DNA duplexes by in situ photon-in/photon-out soft X-ray spectroscopy

• Published in: Journal of electron spectroscopy and related phenomena 2010, Vol.181 (2), p.197-201
• Main Authors: Guo, J.-H., Kastanov, S., Soderstrom, J., Glans, P.-A., West, M., Learmonth, T., Chiou, J.-W., Luo, Y., Nordgren, J., Smith, K., Pong, W.-F., Cheng, H., Griffiss, J.M.
• Format: Article
• Language: English
• Subjects: A-T pair; Analytical chemistry; Analytisk kemi; A–T pair; Chemistry; DNA; Electronic structure; Fysik; G-C pair; G–C pair; Kemi; NATURAL SCIENCES; NATURVETENSKAP; Physics; RIXS; Soft X-ray absorption and emission spectroscopy; Spectroscopy; Spektroskopi
• ISSN: 0368-2048; 1873-2526; 1873-2526
• DOI: 10.1016/j.elspec.2010.05.014

Understanding protein functionality is of fundamental importance in biochemistry. Soft X-ray transitions, where the core-level vacancies are filled by the valence-orbital electrons, give direct information about the chemical bonding. Soft X-ray absorption and emission study of poly(dG) -poly(dC) in aqueous solutions can elucidate the relation between the structure and functionality of proteins. We report the N K-edge soft X-ray absorption (XAS) and resonant soft X-ray emission spectroscopy (XES) to characterize the electronic structure near the Fermi level of DNA duplexes to specify the charge migration mechanism. Since N atoms are included in only bases in DNA duplexes, the XES spectra excited from N 1s to unoccupied states purely extract the electronic orbital features of the bases in DNA. The fact that N atoms in different bonding environments form well-defined structure has been determined. The experimental findings provide the evidence for the charge-hopping and/or charge-transfer effects in understanding of electric conduction in DNA duplexes when electrons pass through the π* states of DNA bases.