[phenixbb] difference density maps

[rpai at berkeley.edu]

Hi,

I have a question on difference density maps.

We are soaking in a substrate into my enzyme and am trying to see if it is
in there by looking at difference density maps.

We looked at an fobs-(fobs-fcalc) map and see density and 5 sigma at each
catalytic active site in roughly the same place, its not great, but it
seems like there is something there.

so then, I thought I would confirm this by an fobs-fobs map.

But I just used the phenix fobs-fobs difference electron density map and I
dont see anything there.

So I am curious as to an explanation of the difference.

Any ideas?
Raj