Paul, N.; Paul, A.; Steitz, R.; Kreuzer, M.; Lux-Steiner, M.Ch.: Selective Self Assembly of Glutamate Molecules on Polyelectrolyte Multilayers. The Journal of Physical Chemistry B 116 (2012), p. 4492-4499

The adsorption behavior of neurotransmitter biomolecule, glutamate, on terminal poly-(allylamine)hydrochloride (PAH) polyelectrolyte multilayer is compared with its adsorption on a terminal poly(styrenesulfonate) (PSS) polyelectrolyte multilayer. Using X-ray and neutron reflectivity experiments, the internal structure of such a supramolecular film has been revealed with high resolution and the volume fraction of the adsorbed glutamate is determined. It has been shown that the glutamate binds only to the terminal PAH multilayer. Multiple attenuated total reflection infrared spectroscopy indicates that glutamate is electrostatically physisorbed on PAH surface in the zwitterionic form. Index matching neutron experiments have been done where the scattering length density of the solvent is varied, by changing the ratio of heavy water and light water, until it completely matches with that of the polyelectrolyte layer. The resulting absorption of the glutamic acid leads to changes in scattering profile which are analyzed and it is seen that the adsorption is restricted only to the surface layers. On the other hand, terminal poly(styrenesulfonate) multilayers show resistance toward glutamate. Such repulsion and adsorption between the neurotransmitter and polyelectrolytes could be potentially used in a variety of medicinal applications.