[3dem] amplitude contrast valuesHi,

[David Gene Morgan]

Hi,

	I'm trying to do some automated defocus determination (initially trying 
Niko's ctffind3 program) and would like some input on appropriate 
amplitude contrast values for various types of samples.  I know that ice 
embedded images usually are said to have an amplitude contrast of 0.07 
to 0.1.  I also know that with protein/nucleic acid complexes in ice, 
amplitude contrast may need to be set a bit higher (say to as much as 
0.15 for some data I worked on awhile ago).

	But I don't have any sort of feeling for appropriate values of 
amp;itude contrast for different sorts of negative stains (either cryo 
negative stain or standard negative stain).  It should be "high," but I 
don't know how high might be appropriate.

	If anyone has either some practical or theoretical insight into this, 
I'd appreciate some suggestions.  Also, does anyone know about an 
appropriate amplitude contrast for a standard Au/Pd waffle grid?

	Thanks in advance for all your help.

-- 
                  David Gene Morgan
              Electron Microscopy Center
                   047D Simon Hall
                   IU Bloomington
                812 856 1457 (office)
                812 856 3221 (3200)
             http://bio.indiana.edu/~cryo