Hi Amir, Ade, Mark and Tom,
Thanks a lot for your replies. Checking with BSA is a great idea and I
should've done it earlier. The BSA run for recent experiment is OK. I
cannot find a standard profile for my experiment one year ago. So I
guess that there was something wrong with the machine one year ago.
Besides, as Tom pointed out, 144KD is way off the MW of dimer. So I am
quite confident that I should use the new data.
BTW, the protein concentration is same. And it is a monomer-dimer
equilibrium (11.4ml and 10.0ml).
Zhen
Quoting Amir Khan <[log in to unmask]>:
> Hi Zhen
> -was concentration higher in old run? Might be monomer-dimer equilibrium,
> for recent paper, see Benfield et al. (JBC, in press)
> -we have a miniDAWN with a 'low-high-medium' setting in the back of
> the setting.
> Inadvertently changing the setting scales the MW values up and down.
> Have you run a BSA standard, to insure system is OK?
> -Amir
> ________________________________________
> From: CCP4 bulletin board [[log in to unmask]] On Behalf Of zhen
> zhang [[log in to unmask]]
> Sent: Thursday, April 21, 2011 5:32 PM
> To: [log in to unmask]
> Subject: [ccp4bb] Puzzle with MALS
>
> Dear All,
>
> I am having a consistency issue processing my SEC-MALS data. The
> sample is a 80KD protein which may form a dimer. The experiment I
> run a year ago shows a major peak at 11.4 ml (GE S200 column), which
> is calcuated to have a MW of 144kD. There is a minor peak at 10.0
> ml. In an effort to make nice looking pictures, I rerun the
> experiement using the same setup (column, buffer, protein, speed)
> and again the major peak is at 11.4 ml but it is calcuated to have a
> MW of 80KD. I rerun the sample multiple times with the same result.
> I tried to reprocess the old data and the calcuated MW is still
> 144KD. I am puzzled about what I have done wrong and which data I
> should trust. Well, I am inclined to trust the later experiment
> because I took extra caution and had multiple data sets. However, I
> should be able to reprocess the old data to have a MW close to 80KD
> if I can find out what is wrong and correct the mistake, which I
> have not been able to. Any suggestions?
>
> Zhen Zhang
>
>
>
>
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