Do I need to use a linker to bind my ligand to the particle to avoid steric hindrance issues?
Linkers usually imply a low molecular weight compound such as a heterobifunctional linker with molecular weight below 1000. In coupling to noadsorptive solid phases linkers have proven value by increasing the accessibility of reactive sites on the protein. Hovever, linkers are of no value in coupling to polystyrene microparticles. Proteins bind to PS MP by adsorptive interactions . This is true even with covalent coupling protocols. Adsorption happens very rapidy and covalent interactions follow with slower kinetics. Thus, it is the rapid adsorptive interactions which determine the orientation of a bound protein. Note also that the size of typical linkers is very small relative to any protein that is being coupled to a microparticle. So the belief that a linker will act as a so called spacer arm is incorrect. The use of albumin as a carrier for haptens such as drugs of abuse or monitored drugs does have value as a spacer. Here a large molecule, albumin, presents a much smaller molecule
