Absolute Mag™ Streptavidin Iron Oxide Nanoparticles, which are coated with amphiphilic polymer, are water soluble materials and covalently linked with streptavidin. These particles are very stable in most buffer solutions. Their zeta potential ranges from -20mV to -40mV. Their organic layers contain both monolayer of oleic acid and monolayer of amphiphilic polymer, whose thickness is about 4nm. The target molecules are always biotinylated molecules such as DNA, peptide and protein. Also for the reaction between biotinylated molecules and AMS, it's necessary to use monobiotinylated molecules, which have only one biotin linked to each biomolecule, to avoid aggregation of nanoparticles.