I am using a buffer insoluble peptide for EGFR protein interaction study. For all other purpose I generally use 1% DMSO while preparing solutions. Do I need to add 1% DMSO in SPR buffer while running SPR. Also, for protein coupling/immobilization, is it fine if I use DMSO containing buffer. As I heard, DMSO also have high RI, how can I be sure the graph is from peptide, not from DMSO.
DMSO has some effect on the refractive index of the solution, hence will give a bulk effect. To reduce the difference in bulk effect between flow buffer and sample you can add DMSO to the flow buffer.
You can immobilize a ligand dissolved in DMSO. Assuming that you use the amine-coupling I would try the lowest DMSO concentration possible. If you use the build-in immobilization protocol this will probably not go well since the instrument does not take into account the DMSO bulk effect. It is better to immobilize ‘by hand’. After activation, inject the ligand for a short period and stop. Wait until the new baseline is established and calculate how much ligand is coupled. Inject the ligand again if more is to be immobilized. And finish with the deactivation.