about the life of the immobilizated chip

hi,Arnoud
I have some questions for your help.this is the problem:
At 2017.08.25 , I used a new CM5 coupling anti human IgG Fc to test antibody P034035,
The result is normal, as follows:
At 2018.02.01, I used the same chip to test P034035. Other’s conditions are the exactly the same.
The result is as follows, It doesn’t regenerate well.
I try to change a new chip, the result is normal.
I guess it's the chip, but why would the regeneration be bad to keep the chip in the buffer for a while? What are the reasons for this? Can you give me some answers?

Hi,

Generally the lifetime of a sensor chip surface (ligand) is determined by what you do with it. Each cycle of binding, dissociation and regeneration will usually destroy some of the ligand molecules. In addition, storage can also make the ligand molecules less functional. Only store sensor chips that are clean (no analyte present) and well equilibrated (no regeneration solution left). Storage in flow buffer at 4°C (with some sodium azide) is often recommended. However, this is not always the best condition. Some molecules benefit from higher or lower storage pH or higher salt content in the buffer. Optimal conditions are to be determined empirically. And some proteins don't like to be stored at all and we don't know why.

You already confirmed with a new chip and fresh ligand and analyte are working as before. So back to the stored chip. Indeed the picture looks weird with the upward drift. I trust that you have washed the chip on both sides with clean water and dried the sensor side with a lint-free cloth. The functional side you can dry by holding a tip of lint-free cloth in the corner before you insert it in the casing. Failing to dry the chip can insert liquid droplets on the optical interface which can give erroneous curves.
After inserting a stored chip we run some time at full flow rate to equilibrate fully with fresh buffer.

For your specific situation I don't have a precise answer.

Kind regards
Arnoud