We have recently performed an SPR screen for small molecules against a CM5-chip bound protein. The samples contained DMSO, yet being "rookies" to this method, we did not add DMSO to the running buffer. We now understand this to be a mistake, and are preparing to rerun with DMSO in the running bugger.
We understand that some of our "hits" from the first screen may be false positives (effects of DMSO), so we will rerun all of the hits. My question is - do we need to also rerun the negatives? i.e. - is it possible that not adding DMSO to the running buffer resulted in false negatives?
I have no experience with this kind of 'mistake'. If there are not too many samples and there is enough of each sample, I would repeat all the compounds (e.g. overnight run). In addition, rerun the positives at different concentrations to verify that they are real interactions. You could try to match all the samples to the same DMSO concentration to rule out any differences there. If you really want to compare different compounds you should also do some DMSO calibration to compensate for small DMSO differences.