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Hi,
Our lab has recently got an Innova AFM. My question is that dose it have the capability to scan membrane proteins? I have been working on it for the past two months and found that the instrument is unstable and the results not reproducible. I haven't been successful in scanning nanoscale molecules. Moreover, I haven't seen any published papers using Innova. I just don't know why. Could any tell me? Thank you!
Zhuoyang
Dear Zhouyang, I do not have experience on the innova, but I do have some experience with membrane proteins. IN general, it is more likely that sample perparation/scanning optimisation is hampering your results than the inherent capabilities of the instrument. I would be fairly certain that the isntrumetn has the resolution required.
How are you scanning these proteins? How are they fixed on the surface, and what environment are you using? Scanning in liquids, with biological samples can be challenging.
Pete.
My (limited) understanding on imaging membrane proteins is that the preparation is key which should be independent of the Bruker AFM used. I am sure you have seen this paper:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1614478/
Getting data like that should absolutely not be a problem with the Innova. Better even, Innova would get these data in closed-loop xy. A few things I would suggest looking out for:
1. Make sure that your fluid holder is cleaned before an experiment. Typically washing it with very little detergent, thorough rinsing with destilled (not just deionized) water, and drying will do.
2. For Tapping Mode operation using the SNL C-lever or equivalent. This lever will excite very nicely around 15 kHz on Innova. Once you are a bit closer to the surface you should get a reasonably clean peak. For the first 5 minutes or so you may want to pull the z-piezo back 500nm or so and re-tune.
3. The deflection sensitivity of Innova is significantly higher than on an MM. So do not get concerned if you see some detector movement in the beginning. Once the system is in (thermal) equilibrium this will disappear.
4. Your experiment space should be setup properly but if it is not or in case you are using an older software version it is beneficial to check that your closed-loop xy feedback settings are lower than they are for air. In case you see some oscillations just reduce the I parameters until they disappear and save those settings for the future.
5. Enjoy your Innova and enjoy getting great results