Sensorgram with a grey background

Hi everyone,

I'm working on protein interaction using a BIAcore 3000 system.
Today when I use the machine. I saw my Sensorgram with a grey background when I choose single flow cell, the value was pretty high. After I dock my CM5 chip, the signal of 2-1 3-1 and 4-1 was -75000 around.

Dose anyone know what's the problem?

Thanks!
Jakcie.

Hi Jackie,

In general this is a sign that the optical system is not working properly.
In most cases there is air on the sensor chip. Or you docked a maintenance chip!

First prime to flush out the air and run a sensorgram again.
Not good. Undock and inspect the sensor chip. It should be clean on both sides.
Dock again and run a sensorgram. It should be ok now.
If not you can try another chip or you have to call in the maintenance engineer.

Kind regards.

Thanks for your quick reply!!!

I ran Prime, Flush, Unclogging and desorb using a maintainace chip and then check my own CM5 chip. The Signal of most flow cell become normal but it's still about twice higher than what I get last time. Dose this mean there is still some air in the system?

Thanks!
Jackie.

Hi Arnoud,

When you said inspect the chip. Did you mean check the golden surface?
I took a picture of the surface of my chip. It seems there are something stuck on it.

Would this be a problem?

Thanks so much!

Jackie.

The gold surface should be perfectly clean on both sides.
This looks as if it is some buffer residue.

You can try to wash the surface and dry both sides with a clean tissue. Dry only the sides of the gold surface and dry also the glass side. You can also use air or a stream of nitrogen to dry the surface.

Depending on what is on the chip my experience is that a baseline with HBS is within 14000 - 25000 RU.

Thanks Arnoud,

I never know that I can wash the surface by hand. :woohoo:
I'm a little worried if I would wash away any immobilized ligand during washing.
Is this a problem?

Thanks!

Jackie.