title: Paramagnetic NMR investigation of dendrimer-based host-guest interactions.
abstract: In this study, the host-guest behavior of poly(amidoamine) (PAMAM) dendrimers bearing amine, hydroxyl, or carboxylate surface functionalities were investigated by paramagnetic NMR studies. 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) derivatives were used as paramagnetic guest molecules. The results showed that TEMPO-COOH significantly broaden the ¹H NMR peaks of amine- and hydroxyl-terminated PAMAM dendrimers. In comparison, no paramagnetic relaxation enhancement (PRE) was observed between TEMPO-NH₂, TEMPO-OH and the three types of PAMAM dendrimers. The PRE phenomenon observed is correlated with the encapsulation of TEMPO-COOH within dendrimer pockets. Protonation of the tertiary amine groups within PAMAM dendrimers plays an important role during this process. Interestingly, the absence of TEMPO-COOH encapsulation within carboxylate-terminated PAMAM dendrimer is observed due to the repulsion of TEMPO-COO- anion and anionic dendrimer surface. The combination of paramagnetic probes and ¹H NMR linewidth analysis can be used as a powerful tool in the analysis of dendrimer-based host-guest systems.
authors.affiliation: Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, People's Republic of China.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Naimin
authors.initials: N
authors.lastname: Shao
authors.forename: Yiyun
authors.initials: Y
authors.lastname: Cheng
mesh_terms: D000588:Amines / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D050091:Dendrimers / Q000737:chemistry*; D006878:Hydroxides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013499:Surface Properties
chemical_list: D000588:Amines; D001672:Biocompatible Materials; D002264:Carboxylic Acids; D050091:Dendrimers; D006878:Hydroxides; C104700:PAMAM Starburst; C031356:hydroxide ion