1. Two antiparallel sets of hydrogen bonds (arrows) bind glycine
Glycine is the smallest and most highly represented of the 20 amino
acids that comprise the primary structures of all proteins. It is
especially prominent in loops and irregular regions connecting sequences
parts of the protein that have folded into more ordered secondary
We have recently discovered that the electrical conductance of
a-glycine crystals exhibit extraordinarily
large increases (4 orders-of-magnitude) as the temperature is decreased.
The dependence of the conductance on temperature also displays strong
hysteresis; an effect that is mirrored in equally extraordinary
variations of the electrical capacitive properties with temperature.
The crystal exhibits a very unusual inductive behaviour (negative
capacitance) not expected for a passive “device”.
2. Anomalous dependance of the conduc-tance of glycine on
Our recent neutron diffraction studies of a-glycine have revealed
a small temperature dependence of spatial separations of the glycine
layers and minor changes in the interlayer hydrogen bonds. However,
the neutron diffraction data cannot explain directly the magnitude
of the changes that we have observed in the electrical properties
of these crystals.
3. Anomalous dependance of the capacitance of glycine on temperature.
The investigations on glycine will be extended to highly ordered,
essentially “2-dimensional”, glycine structures on 111-atomically-flat
silicon using a new method that we have developed for attaching
organic molecules to Si-H surfaces (see ‘Organics-on-silicon’
article). The aim is to determine the origin of the anomalous electrical
properties in the crystal and to shed light on any biological significance
of these anomolous electrical properties.
This work is a collaboration between the School of Physics (Biophysics),
School of Biotechnology and Biomolecular Sciences and Biosciences
Division (Los Alamos National Laboratory).
Benno Schoenborn, Terry Chilcott, Paul Langan,
Hans Coster and Kevin Barrof