[3dem] [TEM] amplitude contrast

Philip Koeck Philip.Koeck at ki.se
Tue Aug 15 06:05:20 PDT 2017


Thanks for your answer, Steve.

One clarification: By specimen thickness I meant actual protein thickness, for example 2 layers of catalase rather than 1,
or a long cylindrical molecule in top view rather than side view.
Wouldn’t that lead to a big difference in percent amplitude contrast if amplitude contrast is due to multiple scattering?

Från: Ludtke, Steven J [mailto:sludtke at bcm.edu]
Skickat: den 15 augusti 2017 14:48
Till: Philip Koeck
Kopia: Sacha De Carlo; 3dem at ncmir.ucsd.edu
Ämne: Re: [3dem] [TEM] amplitude contrast

If it’s due to multiple scattering, it must depend strongly on specimen thickness.
If it’s due to inelastic scattering, why is it so weak (about 10%)? Inelastic scattering has a larger cross section than elastic, I believe.

Clearly the attenuation of the beam is impacted strongly by specimen thickness. However, the effect you are referring to as amplitude contrast is due to the difference in scattering in one part of the specimen vs another. That is, uniform solvent added above or below the feature producing contrast simply attenuates the beam uniformly, and doesn't produce "contrast".


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