In this work, classical molecular dynamics (MD) simulations have been used to provide unique insights on the nature and extent of intermolecular interactions present in a phenylalanine anilide (PA) molecularly imprinted polymers (MIP) prepolymerization mixture.

Molecular Imprinting is a technique for producing highly selective synthetic receptors for a predetermined molecular structure, and involves the formation of cavities in a synthetic polymer matrix that are of complementary functional and structural character to a template molecule.¹ It is generally accepted that the recognition properties of a MIP is a product of the interactions between monomers and template during the prepolymerization stage. Accordingly, studies of the nature and extent of the interactions present in prepolymerization mixtures, in patricular those involving template, should yield information which can be related to the observed recognition properties of the final MIP.

Phenylalanine anilide MIPs have been the subject of a significant number of studies aimed at producing an understanding of the mechanisms underlying the recognition processes. Interestingly, two different models have been proposed to explain the behaviour of PA-MIPs. Studies by Sellergren et al. proposed that template selectivity, was a consequence of  the presence of a functional monomer-template complexes of 2:1 stoichiometry.² Later, however, Katz and Davis proposed an alternative model,³ where the template (PA) recognition sites in the MIP were suggested to arise from functional monomer-template complexes of 1:1 stoichiometry in combination with the presence of higher order template-template complexes.

To resolve this conjecture, we performed a series of MD studies, the results of which demonstrated both the presence of PA-PA self association complexes, and that the most statistically prevalent monomer-PA complex stoichiometry was of a 1:1 nature, though differetn in character from that proposed by Katz and Davis.  Moreover, the role of cross-linker in forming recognition sites was apparnet in these studies, a fact not previously considered.

References

1. Alexander C, Andersson HS, Andersson LI, Ansell RJ, Kirsh N, Nicholls IA, O’Mahony J, Whitcombe MJ. Molecular imprinting science and technology: A survey of the literature for the years up to and including 2003. Journal of Molecular Recognition 2006;19:106-180
2. Sellergren B, Lepistö M, Mosbach K. Highly enantioselective and substrate selective polymers obtained by molecular imprinting utilizing noncovalent interactions. NMR and chromatographic studies on the nature of recognition. Journal of the American Chemical Society 1988;110:5853-5860
3. Katz A, Davis ME. Investigations into the mechanisms of molecular recognition with imprinted polymers. Macromolecules 1999;32:4113-4121