Specially in the case of cyclodextrin, Crown ether system which would be more superior??
Cryo-EM is still budding if high resolution is considered. Both techniques have their own advantages and limitations.
Cryo-EM
1. When you have high molecular weight complex, membrane protein where sample amount is limited
2. Prior information say homology model is required.
3. At present not suitable for completely novel fold
4. Difficult to get resolution higher than 4A (with few exceptions)
5. Specific interactions : Difficult to claim
Crystallography:
1. If you have ample amount of homogeneous protein, go for it
2. Getting a good diffracting crystal not always possible
3. Resolution can be improved
Coming to cyclodextrin is very good cryoprotectant for CryoEM. It all depends on what protein you are working
I would say if the molecules are willing to crystallize, a diffraction method will always give you way higher resolution. (Of course, one may argue that the conformation of a molecule in a crystal packing can be different from the conformation in solution, which difference might be quite relevant for bio molecules.)
Moreover, if you want to measure the structure of cyclodextrin and crown ethers, they are both too small for cryo-EM. I vaguely remember the lower limit in molecular size is about 150 kDa (there are different opinions, though they are always above several tens of kDa).
Anyhow, there is also a method in between which is Electron Diffraction!
It is also named EDT (electron diffraction tomography). In principle it is a single-crystal diffraction experiment like in XRD. It's main advantage is ED requires much smaller crystals (max100-200 nm in thickness) that are unsuitable for XRD. If the sample is vacuum-sensitive or beam-sensitive, the measurement can be done in cryo-conditions, similar to cryo-TEM.
With the current state of the art and availability, no doubt, concentrate your efforts in getting nice crystals about 0.3 mm wide. There are plenty of places everywhere to measure them, better at low temperature. With good crystals and even using an old style diffractometer you can obtain precise atom positions for it.
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography