Dear Austin,
The 2D class average images should look like true projections, as they are
merely the average of many individual particles, each of which is of
course also a projection. So your interpretation of the 2D class averages
until recently was not correct: you will see 'everything' in the path of
the electrons, not just on the face of the particle.
HTH,
Sjors
> After some searching, I couldn't find an answer to this question.
>
> Up until recently I had always seen 2D classes similar to looking at
> different angles of a solid object (like I was rotating the protein in my
> hand). I see a surface. This is different from a 2D projection, which I
> have always seen as 3D density information flattened into a 2D image. In a
> projection, features have no context in the z-axis. So if you see
> something, you wouldn't be able to tell its absolute position on the
> particle, only its relative orientation.
>
> I had always seen classes as the opposite: if you see features in a 2D
> class, it is on that face of the particle.
>
> Is that true? Or do I have my understanding mixed up? Recently some of our
> classes (Relion) have shown features we expected on a different face
> (based on biochemical data).
>
> Thank you for indulging a lowly assistant :)
> - Austin Dixon
>
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--
Sjors Scheres
MRC Laboratory of Molecular Biology
Francis Crick Avenue, Cambridge Biomedical Campus
Cambridge CB2 0QH, U.K.
tel: +44 (0)1223 267061
http://www2.mrc-lmb.cam.ac.uk/groups/scheres
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