Paramagnetism-Assisted Nuclear Magnetic Resonance Analysis of Dynamic Conformations and Interactions of Oligosaccharides

Abstract

Nuclear magnetic resonance (NMR) spectroscopy has considerable potential for describing dynamic oligosaccharides at the atomic level in solution and in complexes with other biomolecules. However, conformational restraints primarily provided through measurements of nuclear Overhauser effect and spin–spin coupling, which act as information sources about local conformation, are insufficient, limiting the adequate carbohydrate characterization by conventional NMR approaches. Recently developed paramagnetism-assisted NMR techniques have addressed this issue by exploiting the effects of magnetic dipole–dipole interactions between nuclei and an unpaired electron. This method is utilized to describe the overall conformation of oligosaccharides. Specifically, paramagnetic probes, such as a lanthanide-chelating tag and a nitroxide radical, are employed to determine the geometrical arrangements of individual nuclei in the target oligosaccharides relative to the paramagnetic center position. Inspection of paramagnetic effects such as pseudocontact shift and relaxation enhancement, in conjunction with molecular dynamics simulations, gives atomic long-distance information – extremely valuable data for characterization of conformational dynamics and interactions of oligosaccharides.