Channel mismatch?

Hi,

I'm a newbie to the SPR technique and got two unwanted spikes at the start and end of the sample injection, as shown in the attached picture. The biacore assay handbook suggests it may result from misalignment of the
reference and active sensorgrams. As I checked them individually, the signals of reference sensorgrams do come 1-2 secs earlier than the active sensorgrams.
Is there any way to adjust the alignment, as the spikes are so high that it affects kinetic analysis.

Many thanks to those whom may help.

Hi,
Since you do not mention how the data was processed the answer is more general (also see www.sprpages.nl/experiments/data-processing ).
Most evaluation programs align the data automatically or you can do it by hand. In general the data is aligned in discrete steps (e.g. 1 or 0.1 seconds) therefore there will be always slightly misaligned curves. This effect is more pronounced when the original data contains larger jump (bulk effect) at the start and end of the analyte injection. So, lowering the bulk shift during analyte injection may be an option. In addition, slower flow rates give a larger time delay between the channels.

Ultimately you can export the data as [time – response] pairs and align the time by hand (e.g. in excel) and import the data again to analyse.

Kind regards
Arnoud

Hi Arnoud,

Thanks a lot for your prompt reply. Guess I need to adjust the time by hand.
Say I export the time-response datas and re-align them, how do I import into the evluation software (I'm using Biacore X100), or shall I evluate the data by external softwares? If the latter, any suggestions?

Many thanks!

It seems that you cannot import files other than the original files from your instrument. Most likely due to the fact that imported files don't have the report point information any more.
As an external evaluation program I am very fond of Scrubber ( www.sprpages.nl/software-weblinks ).

Arnoud.

Dear Arnoud,

Thanks so much for your kind advice.
The buffer of anlyte and ligand is exactly the same, though the analyte is DNA and I don't know whether it could be the cause of bulk effect.
One more question. Can I adjust flow rate in the X100 control software? If so, how?

Again, many thanks.

Interestingly I find comparisons with the X-100 that the flow should be between 1 – 100 µl/min but nowhere in the manual is a reference to the flow rate. Maybe it is possible within the wizards?

Arnoud