Monitoring Glycan-Protein Interactions by NMR Spectroscopic Analysis: A Simple Chemical Tag That Mimics Natural CH- Interactions
Luis P. Calle, Begoña Echeverria, Antonio Franconetti, Sonia Serna, M. Carmen Fernández-Alonso, Tammo Diercks, F. Javier Cañada, Ana Ardá, Niels-Christian Reichardt, Jesús Jiménez-Barbero
Detection of molecular recognition processes requires robust, specific, and easily implementable sensing
methods, especially for screening applications. Here, we propose the difluoroacetamide moiety (an acetamide bioisoster) as a novel tag for detecting by NMR analysis those glycan–protein interactions that involve N-acetylated sugars. Although difluoroacetamide has been used previously as a substituent
in medicinal chemistry, here we employ it as a specific sensor to monitor interactions between GlcNAc-containing glycans and a model lectin (wheat germ agglutinin). In contrast to the widely employed trifluoroacetamide group, the difluoroacetamide tag contains geminal 1H and 19F atoms that allow both 1H and 19F NMR methods for easy and robust detection of molecular recognition processes involving
GlcNAc- (or GalNAc-) moieties over a range of binding affinities. The CHF2CONH- moiety behaves in a manner that is very similar to that of the natural acetamide fragment in the involved aromatic-sugar interactions, providing analogous binding energy and conformations, whereas the perfluorinated CF3CONH- analogue differs more significantly.