Measurement of glycan-based interactions by frontal affinity chromatography and surface plasmon resonance.

Proteins and lipids are often modified with glycan chains, which due to their large hydration effect and structural heterogeneity, significantly alter the surface physicochemical properties of proteins and biomembranes. This "glyco-atmosphere" also serves as a field for interactions with various molecules, including other glycans, lipids, peptides, proteins, and small molecules such as neurotransmitters and drugs as well as lectins. Therefore, sensitive techniques for measuring these glycan-based interactions are becoming more and more necessary, with the appropriate method largely depending on the interacting molecules. In this chapter, we focus on frontal affinity chromatography (FAC) and surface plasmon resonance (SPR) for examining polysialic acid-involved interactions with neurotransmitters and neurotrophins. FAC is characterized by its applicability to analyze weak interactions that are difficult to measure using conventional methods, and by the ease of principle and experimental procedures. SPR is advantageous due to the availability of suitable surface materials and for real-time monitoring with nonlabeled analytes.