[3dem] Regarding Image Quality from FEI Tecnai G2 Polara

[Sayan Bhakta]

Hi,
We are facing many problems with our Cryo EM facility. I am giving some
details of the machine and one of the main problems we are facing. It would
be very helpful if people comment on this and help us to find the actual
problem.

Machine:
FEI Tecnai G2 Polara
300Kv
Have been running for last two years.

Camera:
FEI Eagle 4k*4K

Problem:
On the first day when we are putting our sample into the Cryo EM, we are
getting good images. From the second day the quality of the images
deteriorates.

1.  If we look at the images taken on the first day and second day, the
intensity values of the images decreased on the second day.
2.  From the FFT, we see nice thorn rings from the images taken on the
first day. But for the images taken in the second day, the FFT is very bad.
Most of them are having drifts.
3. Irrespective of the days, there are some images for which the 1D
spectrum is having a cut in between. What I mean by that is there is
spectrum upto certain distance in the 1D spectrum, then there is no waves,
then again there are some waves.
4. Irrespective of the days, images are sometimes with blakish shadow on
one side and with whitish shadow on other side. We need to do gain
correction more frequently than usual- a number of times in a day.

For your information:

1. The vacuum is stable on the second day.
2. We are giving Cryo-cycle each weekend.


If anyone has ever faced the same problem or has any advice on this regard,
it would be very helpful. We have been struggling very hard to standardise
many issues with our microscope.
-- 

Sayan Bhakta

Research Scholar

Group of Dr. Jayati Sengupta

CSIR - Indian Institute of Chemical Biology

Kolkata, West Bengal

India
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