CHARACTERIZATION OF THE N-RETINYL-3-SILYL-N-PROPYLAMINE MOIETY IN SOLUTION BY NMR-SPECTROSCOPY AND COVALENTLY BOUND TO CELITE BY HYDROGEN-ION BINDING

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 p reviously observed pH dependence of beta-lactoglobulin binding by this affinity matrix. N-Retinyl-3-(triethoxysilyl)-n-propylamine was synth esized as a soluble model compound for the affinity ligand. C-13 NMR a nd H-1 NMR spectra of this compound and its precursors, (3-aminopropyl )triethosysilane, all-trans-retinal, and the Schiff base, confirmed fo rmation of the Schiff base and its selective reduction with NaaCNBH(3) . Furthermore, H-1 NMR spectra confirmed that protonation of the secon dary amine in N-retinyl-3-(triethoxysilyl)-n-propylamine occurred upon treatment at pH 5.1.