  In the present study, a prototypical reaction in biochemistry involving a
well-known bio-molecule called imidazole (C3H4N2) and its known affinity
towards transition metals (such as Co, Ni, Cu, Fe, etc.) has been used to
illustrate and exemplify the use of ballistic conductors as probes for
molecular reactions at the quantum level. Atomic point contacts of transition
metal Co were made using electro-deposition, followed by their reaction with
imidazole in an aqueous solution. As the imidazole molecules covalently bond
with the Co atoms, the quantized conductance of the nanocontact decreases, thus
providing a quantum probe for studying molecular reactions. During the course
of the reaction, different conductance channels within the nanocontact become
unavailable due to covalent bonding of Co with imidazole, thereby also
providing a means of studying the number of channels contributing to the total
conductance in the nanocontact itself.
