What type of binding interaction is most likely between proteins and dextran in size-exclusion chromatography?

• A. Aromatic
• B. Hydrophobic
• C. Salt bridge
• D. Hydrogen bonding

Answer: (D)

In size-exclusion chromatography, the separation of proteins and other biomolecules is based on their size, allowing smaller molecules to enter the pores of the stationary phase while larger molecules are excluded. Dextran, which is often used in the stationary phase, is a polysaccharide that can create a hydrophilic environment.

The most relevant binding interaction between proteins and dextran in this process is hydrogen bonding. Many proteins contain polar or charged side chains that can form hydrogen bonds with the hydroxyl groups present in dextran. This interaction helps to facilitate the capture of proteins when they fit within the constraints of the chromatography matrix without fully entering its porous structure.

While hydrophobic interactions can also play a role in protein behavior, they are not the primary interaction in size-exclusion chromatography, where the focus is on size rather than hydrophobic complementation. Other interaction types such as salt bridges, which involve ionic interactions between charged side chains, or purely aromatic interactions are less significant in the context of how proteins interact with a dextran-based column under these specific conditions. Therefore, hydrogen bonding is the key interaction facilitating the relationship between proteins and dextran during size-exclusion chromatography.