Use of neutrons reveals the dynamics of cell surface glycosaminoglycans

Cell surface glycosaminoglycans (GAG), such as heparan sulfate (HS) and heparin, are key multifunctional cell regulators, which are involved in numerous molecular events associated with tumor growth, metastasis, pathogen attachment, and immune response. GAG dynamically bind and regulate the activities of many signaling proteins such as growth factors, chemokines, and cytokines. GAG-binding interactions with proteins rely on the coupling between the geometry, flexibility, and rigidity of the polysaccharide chain. Understanding GAG dynamics at the molecular level can therefore provide fundamental insights into GAG function in a cellular context. Elastic incoherent neutron scattering is a powerful tool for the exploration of fast molecular motions in biological macromolecules. Recently, the technique was used to evaluate HS flexibility and rigidity on different timescales between the picosecond (ps) and the nanosecond (ns). Here, neutron spectroscopy experimental procedures are presented, with emphasis on the practical details necessary to prepare samples, run neutron scattering experiments, and extract the dynamics parameters from the data.