Unspecific signals

Hi all,

Lastly I am seeing a lot of unspecific signals like interactions that I did not hope "a priori". Some of these occurs with streptavidin immobilized over the chip.
Is this a normal behaviour?
Usually NaCl buffer concentration is 150 mM and 0.005%Tween20.


Also, only comercial buffer injections show that the signal increases as the injection proceeds.

Any suggestion will be very appreciated

Thanks a lot

How does your non-specific signal looks like? Is a gradual drift up or down or jumps?
Is it on all channels the same?

Which commercial buffers do ou use? Do you repack them e.g. in an other flask?

Arnoud

Hi Arnoud, thanks for replying

The unspecific signals are like a gradual drift up in both FC1 and Fc2 channels of our Biacore X.

I do not repack commercial buffers which are from the same house as the machine is from.

I have seen a paper in which the authors increase the P20 concentration from 0.005% to 0.05% in order to minimize unspecific signals

Yes, you can raise the P20 concentration.

Sometimes a higer salt concentration can be of help but binding is often salt concentration depend. Thus you should check!

I see often drift after changing buffer type or cleaning the machine. This can last for one or two days. Thorough washing of the system is essential. Flowing overnight at 20 ul.min with some injections of the same buffer should stabilize the system.

And last. Calculate your drift back to the machine specifications. Often people want less drift than the machine can deliver.

Arnoud