Molecular Transform Superimposed on a Dataset

From: Bernhard Rupp (Hofkristallrat a.D.)
Date: 13 February 2012 02:10

I found a free program that can be used to quickly play with molecule image
FFTs.

Install Jimage
http://rsbweb.nih.gov/ij/

Load for example my image
http://www.ruppweb.org/images/transparent_molecule.gif
into Jimage
Select FFT, select option complex FFT, and execute.
Zoom in to the center a few times, and you get a real coarse pixelated image
that
looks like my transform. I recall having to scale the FFT range when F90
hardcoding the FT
which I used to calculate the raw data which were then contour-plotted in
Mathcad.

Note that the resulting FFT has 2 parts (use the slider on the bottom),
the real part is always centrosymmetric,
while the complex (phase) part is not.

Probably needs some tweaking to be really useful for presentation purpose.

BR

-----Original Message-----
From: Bernhard Rupp (

This may give some idea:
Illustration of a molecule and its cosine transform:

http://www.ruppweb.org/garland/gallery/Ch6/pages/Biomolecular_Crystallograph
y_Fig_6-16.htm

and sampled by lattice points

http://www.ruppweb.org/garland/gallery/Ch6/pages/Biomolecular_Crystallograph
y_Fig_6-01_PART3.htm

BR