Unconventional Zwitterionic State of L-Cysteine

Research output: Contribution to journalArticle


We report the signature of an unconventional zwitterion in thick (>40 angstrom) L-cysteine films grown at low temperature (100 K) by means of sublimation in ultrahigh vacuum. Using X-ray photoelectron spectroscopy (XPS) we find that protonated amino groups (57%) are less prevalent than in films grown at higher temperatures. A large majority of the protonated amino groups receive the hydrogen through deprotonation of the thiol group (45%) and, in contrast, only a small fraction of the carboxylic groups (13%) is deprotonated. This shows, for the first time, the unconventional zwitterion to be the dominant species in L-cysteine. We believe the unusual growth parameters are responsible for this novel observation.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Sciences
  • Atom and Molecular Physics and Optics
  • Natural Sciences
Original languageEnglish
Pages (from-to)1677-1681
JournalThe Journal of Physical Chemistry Letters
Issue number14
Publication statusPublished - 2011
Publication categoryResearch