accomodating bigger samples in SAXS

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2107086a
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accomodating bigger samples in SAXS

#1 Post by 2107086a » 2016.07.13 17:12

Hey everyone,

I have a protein that oligomerises into long multimers that has an Rg of >300Angstroms. The last time I put it under HPLC-SAXS it eluted in the void volume and it was too big for the camera length. The concentration I used previously was 5 mg/ml. I'm having another beamtime next week and I'm putting the protein in different buffers ranging in concentration of salts and pH to test the effects on the oligomerisation of the protein. I also wanted to change the camera lenght in such a away that it would fit the data for the protein. Hwoever, the beamline scientist told me that the camera length could not be changed currently. Is there any other way of accomodating large samples without changing the camera length? I'm thinking of lowering the sample concentration but also looking for other options as well.

any ideas? :O

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Re: accomodating bigger samples in SAXS

#2 Post by Alex » 2016.07.13 20:13

The last time I put it under HPLC-SAXS it eluted in the void volume and it was too big for the camera length
I think you mean a distance between detector and a sample. At some beamlines this can be adjusted.
I also wanted to change the camera lenght in such a away that it would fit the data for the protein.
do you not see the Guinier region? in other words, why exactly do you want to change detector-sample distance?

I recall some work by Vestergaard and co-workers who studied fibrillation and saw fibrils up to 900A in Dmax, which was
actually at that time the max theoretical possible distance one could see:). Perhaps, this can be helpful and
perhaps you can consider a different beamline:
https://www.embl-hamburg.de/biosaxs/cou ... rgaard.pdf

HTH, Alex

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Re: accomodating bigger samples in SAXS

#3 Post by AL » 2016.07.19 10:43

2107086a wrote:Hwoever, the beamline scientist told me that the camera length could not be changed currently. Is there any other way of accomodating large samples without changing the camera length?
Well, at some beamlines it is possible to change the wavelength.
Basically the smallest angle you need should be qmin < 1/Rg = 0.003 1/A.
Or qmin < pi/Dmax (which is roughly the same value).

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