A solid-state and suspended-state magic angle spinning nuclear magnetic resonance spectroscopic investigation of a 9-ethyladenine molecularly imprinted polymer

Suspended-state high resolution/magic angle spinning nuclear magnetic resonance spectroscopy and solid-state cross-polarization/magic angle spinning nuclear magnetic resonance spectroscopy were employed to study the interactions between 9-ethyladenine and a 9-ethyladenine molecularly imprinted polymer, and a non-imprinted polymer, respectively, both are copolymers of methacrylic acid and ethyleneglycol dimethacrylate. Template-related structural differences between the materials were revealed by contact time measurements and solid-state nuclear magnetic resonance. Rebinding of the template to the imprinted polymer resulted in shorter contact times for nuclei believed to be involved in the binding site interactions whereas the non-imprinted polymer did not exhibit such effects. This indicates that binding site reoccupation has a stiffening effect lowering the mobility of nearby nuclei. More detailed information was obtained from suspended-state saturation transfer difference high resolution/magic angle spinning nuclear magnetic resonance experiments. These revealed molecular level details concerning the interactions of the adenine guests with the polymer binding sites. Thus, a relatively larger transfer of magnetization was observed in the solute when bound to the molecularly imprinted polymer at a position where multiple hydrogen bonds between the analyte and the template can be expected to take place in the molecularly imprinted polymer only.