Wavy sensorgram

Hi Arnoud,
I'm using a Biacore S200 with a CM5 sensor chip. I'm getting results where the sensorgram appears wavy. This result is also inconsistent with other runs where the green line is 2x the analyte concentration of the red line and should be spaced out more. Do you have any suggestion on what is causing the curved lines and the inconsistency between experiments? Thank you.

Hi,
It is difficult to say without the previous sensorgram and the analyte concentrations. It seems that the problems arise with the purple and red curve too because you can observe a large drift before the start of the injection. The curves seem to be processed (bulk is edited out – injection peak). So you need to provide more about the system (ligand – analyte – regeneration – solvents) to get a better answer.
Regards
Arnoud

Hi Arnoud,

Thank you for your response. The previous sensorgram is attached for comparison. The ligand in this study is a DNA hairpin and the analyte is a DNA binding molecule, and the buffer is 10 mM Hepes, 150mM NaCl, 0.05% surfactant P20, 0.01% DMSO. Regeneration is performed with 10 mM Glycine, pH 2.5 for 30 seconds.

I also had the curves switched in my original comment. The red line is 2x the concentration of the green line.

It is hard to say why one of the curves is not as good as the others. Especially when it is only one curve in a series. It could be the mixing, dust particles or some carry over from the previous step. If it stays with this curve I would leave it out. If it happens more often you should clean the instrument en make sure the buffer is free of particles. Mix your samples thoroughly and use caps.
Regards
Arnoud