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Sample Preparation SAXS

For academical use for members of the Heinrich-Heine-University and external users we provide a widespread scientific support and service.

For SAXS experiments the proteins have to fulfill some minimum prerequisites, that will be explained in detail below.

We provide the possibility to perform SAXS measurements. The CSS is equipped with a Xeuss 2 in-house SAXS device from Xenocs. The detector distance is variable from 250 mm to 2500 mm. The system is equipped with a Cu source with a wavelength of 1.5 Å. Samples can be measured in capillaries or small cells. For biological samples we offer the option to use a temperature-controlled flow cell where samples can be automatically injected via a temperature-controlled autosampler.

For a planned SAXS measurement, some aspects are of importance and some documents/chemical agents are needed (see also order form):

  1. the low molar protein buffer should contain as less agents as possible (just as much as is required for protein stability; avoid phosphate buffer and more than 5 % glycerol)
  2. protein needs to be pure (at least 95 % on SDS-PAGE), and homogenous (only one oligomeric state)
  3. protein has to be stable over at least two days (at 4 °C, 12 °C or 20 °C)
  4. protein concentration at least: 5 - 10 mg/ml
  5. minimum protein volume per measurement: 70 µl
  6. please provide about 2 ml protein buffer with declaration of all ingredients. (Important: It has to be exactly the same buffer used for the protein purification/dialysis/concentration for proper intensity determination!)

Furthermore, some information are essential for our experiments:

  1. date of the protein purification and storage/stability conditions
  2. image of SDS-PAGE
  3. homogeneity verification (e. g. gel filtration)
  4. protein concentration, molecular weight, extinction coefficient and composition of the protein buffer
  5. if the protein requires certain ligands (like metal ions, cofactors etc.) for activity and/or stability, please state
  6. Protein sequence including purification tags and cleavage sites (text file)
  7. If available: structure or homology model

For further information or appointments please contact us.

For conduction of the experiments we additionally need some further information about the protein and possibly agents, wherfore we need a filled in order form and therein mentioned documents for every project.

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