Characterization of the N-Retinyl-3-silyl-n-propylamine Moiety in Solution by NMR Spectroscopy and Covalently Bound to Celite by Hydrogen Ion Binding

Abstract

Binding of hydrogen ions by N-retinyl-Celite indicates an approximate pK of 5.6 for the secondary amino group which is consistent with the previously observed pH dependence of β-lactoglobulin binding by this affinity matrix. N-Retinyl-3-(triethoxysilyl)-n-propylamine was synthesized as a soluble model compound for the affinity ligand. 13C NMR and 1H NMR spectra of this compound and its precursors, (3-aminopropyl)triethoxysilane, all-trans-retinal, and the Schiff base, confirmed formation of the Schiff base and its selective reduction with NaCNBH3. Furthermore, 1H NMR spectra confirmed that protonation of the secondary amine in N-retinyl-3-(triethoxysilyl)-n-propylamine occurred upon treatment at pH 5.1. Keywords: N-Retinyl-Celite; N-retinyl triethoxysilyl n-propylamine; 13C NMR spectra; 1H NMR spectra; hydrogen ion binding