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Selective molecular recognition in imprinted polymeric adsorbents and in biological macromolecules

Citation

Sundaresan, Vidyasankar (2002) Selective molecular recognition in imprinted polymeric adsorbents and in biological macromolecules. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:05052011-134334164

Abstract

This thesis describes the synthesis and use of molecularly imprinted polymeric adsorbents for use in ligand-exchange chromatographic separations of structurally similar substrates. A general model of stereo selectivity is also described, which can be applied both to chromatographic adsorbents and to biological receptors. Crosslinking polymerization of trimethylolpropane trimethacrylate (TRIM), under controlled conditions yields macroporous polymers bearing surface-accessible unpolymerized methacrylate residues. These residues have been utilized for copolymerization with different functional monomers to obtain composite polymer matrices with surface coatings of functional polymer chains. Surface modification has been carried out by molecular imprinting, using ternary Cu^(2+) complexes of [N-(4- vinylbenzyl)imino]diacetate and bisimidazole templates, with ethylene glycol dimethacrylate as comonomer. Selectivity characteristics similar to bulk-copolymerized polymers have been observed. The physicochemical characteristics of these functional polymer matrices have been evaluated by ^(13)C NMR, X-ray photoelectron spectroscopy, IR spectroscopy, and scanning electron microscopy. The ability of molecular imprinting to impart enantioselectivity to polymeric adsorbents has been studied using Cu^(2+) complexes of the achiral monomer [N-(4- vinylbenzyl)imino]diacetate and α-amino acids. Crosslinking polymerization with ethylene glycol dimethacrylate as the comonomer yields polymeric adsorbents capable of enantioresolutions of underivatized α-amino acids. Chromatographic adsorbents have been prepared by grafting the imprinted polymer on to silica particles. The observed enantioselectivity increases corresponding to the size of the side chain of the amino acid used as template, with the best enantioresolutions being obtained for materials imprinted against phenylalanine (~1.65 for D,L-phenylalanine enantioresolution). Adsorbents imprinted for alanine show negligible enantioselectivity. Cross-selectivity patterns towards non-template amino acids have been investigated, and the ability of an amino acid imprinted material to resolve analogous chiral amines has been demonstrated. The mechanisms underlying enantioselectivity in imprinted polymers are discussed in terms of the three-point interaction model. This model has been extended to a stereocenter-recognition (SR) model for substrates with multiple stereocenters. For N stereocenters in a linear chain, it has been demonstrated that a minimum of N + 2 interactions need to be distributed over all stereocenters, such that three effective interactions exist per stereocenter. The general applicability of the SR model is demonstrated for biological ligand-receptor interactions, by reinterpreting several previous experimental observations.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemical Engineering
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Arnold, Frances Hamilton
Thesis Committee:
  • Unknown, Unknown
Defense Date:18 September 2001
Record Number:CaltechTHESIS:05052011-134334164
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05052011-134334164
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6376
Collection:CaltechTHESIS
Deposited By: Tony Diaz
Deposited On:16 May 2011 16:56
Last Modified:26 Dec 2012 04:35

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