Elemental XPS spectra of beam protected (unexposed) and irradiated (exposed at different doses) PEG before and after protein incubation.

Abstract

<p>Before (“unexp”) and after (“exp”) helium beam exposure, carbon C1s signals (A) show characteristic alkyl and ether peaks at 284.6 eV and 286.6 eV binding energies, respectively. The presence of oxygen O1s signals (B) at 532 eV and the absence of nitrogen N1s signals (C) at 400 eV also were observed. Subsequent incubation with avidin shows additional C1s peak at 288 eV (D), similar O1s signals at 532 eV (E) and existence of N1s peak at 400 eV (F) binding energies for beam exposed PEG.</p