We ran SPR using dextran chips and always obtained very good data. For example, we can clearly discriminate wide type analytes and mutations. Recently, we failed all SPR works and can't repeat any previous experiments. However, we still can detect good SPR signals using BSA and anti-BAS antibody.

Here is an example to study PDL-1 protein/PDL-1-1 aptamer. You may see good activation, protein immobilization, blocking, but just no protein aptamer binding. Again, we did genearate strong signals using the same materials before (the same proteins and DNA aptamers, which are two months old and stored well at -20C). It seems something changes protein conformation since we know antibody still can recognize BSA even it is denatured. Could it be sodium acetate (pH 4.8) or ethanolamine etc? But how and why? Can anyone pls help us?

Thank you very much!