Solid State NMR: Dynamics in Host-Guest Systems

Dynamic 2H MAS NMR of amino acids in an aqueous environment at the inner surface of meso porous materials

In this project our interest is to study the mobility and interaction of amino acids and small peptides, in aqueous solution, in the vicinity of silica surfaces. We mostly study materials with high surface areas, such as SBA-15 and MCM-41, for gaining better signal-to-noise ratios.

By measuring 1H and 2H MAS NMR at different hydration levels and as a function of the temperature we obtain information regarding the hydration level of our samples (by 1H NMR) and the nature of the guest molecules with respect to the surface (by 2H NMR). We assume that the mobility of the guest molecules near the surface can be described by a two-site exchange model, in which the guest molecules can either be bound to the surface or free reorienting in the vicinity of it.

Because the quadrupole interaction of deuterium is very sensitive to dynamic processes, using 2H NMR spectra we are able to retrieve information regarding the relative amount of guest molecules that are attached to the surface at certain conditions, and do not contribute to the dynamic process, and about the guest molecules that do take part in the exchange process. By comparing their spectral components to calculated ones we can determine dynamic parameters such as the desorbtion rate and the relative amount of bound dynamic molecules at each moment.


  1. The normalized broad components after deconvolution of the 2H experimental MAS spectra of alanine-d3 in a sample of SBA-15 at different p values.
  2. The best fit simulated spectra and their simulation parameters.