Blocking Buffers:
For immobilization of proteins, we recommend using a casein buffer. We have a bead block buffer available (Cat. No. S-4023-025).Elution conditions:
We recommend using a glycine buffer (pH 2.8) for elution. You should collect the antigen in a neutral phosphate buffer, to limit exposure to the harsh pH conditions.Clumping Solutions:
To obtain a mono-disperse population of NanoLink™ Streptavidin beads, these procedures will help:
1. Vortex the beads for 1 minute in their original container to resuspend the pellet.
2. Remove a 10 µL aliquot (mass equivalent to 100 µg of beads) from the dispersed suspension using a P-10 pipette. Add the aliquot directly into a previously prepared solution of 1 M NaCl containing 1% Tween-20 and gently pipette up and down several times to disperse the beads while avoiding foam.
3. Immerse the tube containing the beads into a water bath sonicator (e.g., Branson 1200, 120 volts 50-60 Hz) for three min.
4. Remove a small aliquot of the beads and place them on a standard light microscope (e.g., 100X to 400X) to confirm monodispersity.
5. Once monodisperse, the beads can be washed twice (with a magnet) using molecular grade water. (Note: once the beads are monodisperse, they take a lot longer to pull them to the walls of the tube using a magnetic field (up to two full min).
6. Once the beads are monodisperse, they can be placed into any other suitable buffer you wish with or without Tween-20 and the majority of the population will remain monodisperse. Over time, (for example overnight), the beads will begin to reform aggregates due to the nature of streptavidin itself. This cannot be helped.

Important comments and notes: 1 M NaCl containing 1% Tween-20 combined with sonication does not adversely affect the biotin binding capacity of the NanoLink™ beads. Do not attempt to sonicate or disperse larger masses of beads at one time or in a larger volume. Attempts to disperse the entire volume of beads or even a smaller volume such as 100 µL beads (1 mg) at a single time is not effective. A large amount of sonication energy must be focused on a small volume and mass of beads (e.g., 100 µg in 100 µL) to fully re-disperse the beads into their mono-disperse state. Never use SDS at any concentration in an attempt to disperse the beads since this abolishes their biotin binding capacity.