To the best of my knowledge, x-ray small angle scattering is used to measure the size, shape and structure of macromolecules. Does anybody have any experiense in this field? We used SAXS only for nanoparticle size determining purposes. What kind of instrument should we have for molecular measurements? What do you think about this instrument (http://www.rigaku.com/products/xrd/smartlab), is it good for this purpose?
Generally, for x-ray scattering, and similarely neutron scattering, the spatial resolution, i.e. the size of structures that is resolvalbe, is inverse to the scattering angle the signal is resolved. This means for example for macromolecules like proteins of a few nanometer size have a pronounced scattering pattern at higher angles than for instance colloids of 50 nm. Thus, also particles without a periodic structure can be resolved. Depending on your solvent - water or an organic component - the scattering contrast is significantly affected. In case you are studying proteins, there are plenty good review articles and of course software for free- You should have for instance a look at: http://www.saxier.org/forum/
To my best knowledge SAXS is used for periodic structures (such as lamellar structures in folded polymer crystals) or for other, well defined structures (e.g. core-shell structures, lipid vesicles with multilayers etc.), where the scattering function can be calculated in advance and the parameters can be fitted. For independent macrmolecules in solution rather light scattering, neutrons scattering and similar techniques are used.
Generally, for x-ray scattering, and similarely neutron scattering, the spatial resolution, i.e. the size of structures that is resolvalbe, is inverse to the scattering angle the signal is resolved. This means for example for macromolecules like proteins of a few nanometer size have a pronounced scattering pattern at higher angles than for instance colloids of 50 nm. Thus, also particles without a periodic structure can be resolved. Depending on your solvent - water or an organic component - the scattering contrast is significantly affected. In case you are studying proteins, there are plenty good review articles and of course software for free- You should have for instance a look at: http://www.saxier.org/forum/
After the checking of the measurement range, I would propose SAXS/SANS combo, but I do not think that you would see anything with a table-top X-ray mashine using one single detector. Go to a larger source.
For organic nanoarticles the best technique is SANS/USANS, X-rays are blind for . In fact neutrons are strongly sensitive to H and you can you the fact that the cross section is completely different for hydrogen and deuterium you can use contrast method to enhance the signal coming from your sample if it is in solution.
Doing SAXS on proteins/macromolecules is feasible with a lab-source. In our laboratory we have Nanostar provieded by Bruker. With this machine we are able to measure SAXS signals from proteins or polymers.
The answer to your question, if the instrument which you have linked is suitable for your SAXS is no. Because this machine is optimized for X-ray diffracation (XRD). Check the internet site of Rikagu, they have also dedicated SAXS machines with 2D detectors, which are optimized for such experiments. http://www.rigaku.com/products/saxs
Yes, it depends on the molecule sizes and their contrast level in the solvent. For example, we measured scattering intensity from heteropolyanions, asphaltenes and etc.
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