Protein immobilization

HI,

There is also the possibility that you change the charge of your chip surface by activating the carboxyl-groups on the dextran matrix. Normally, this does not cause problems in changes preconcentration, but in cases where the difference in charges is very small to cause or electrostatic attraction in the one case (on non-actived carboxyls) or repulsion in the other case (on activated carboxyls) this can give problems.

Try to increase the ionic strength of your buffer to mitigate for these effects, ideally by adding KCl in your buffer, which has a bigger electrostatic effect than e.g. NaCl. As suggested before, the use of Zwitterions in the buffer could also help for mitigation of this effect, HEPES is a good example of such buffer.