Unconventional Zwitterionic State of L-Cysteine

作者：Ataman E; Isvoranu C; Andersen J N; Schnadt J^*; Schulte K

来源：Journal of Physical Chemistry Letters, 2011, 2(14): 1677-1681.

DOI：10.1021/jz2006918

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.

• 出版日期2011-7-21