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Sorry, my question probably was not complete enough. The crystals aren't a membrane protein and in most cases are probably more than one layer thick. They are however quite thin and we can get nice TEM images and diffraction patterns. The fact that they aren't one layer may cause more problems later, but for now I'd like to come up with projection images of a hypothetical unit cell and the corresponding diffraction patterns. Since the crystals lay flat on the grids the beam is essentially aimed directly down one unit cell axis. Thanks, Jeff ________________________________________ From: Jacob Keller [[log in to unmask]] Sent: Saturday, November 27, 2010 5:45 PM To: Jeffrey D Brodin Cc: [log in to unmask] Subject: Re: [ccp4bb] generating 2D projections Assuming that your 2d crystals are membrane proteins and are truly 2d (one layer thick), how can there be a screw axis? JPK On Sat, Nov 27, 2010 at 12:02 PM, Jeffrey D Brodin <[log in to unmask]> wrote: > Hi all, > > I'm currently working on a project where we are attempting to compare a single crystal X-ray structure with 2D crystals we've imaged with TEM. I have nice 2D cyrstals and low dose cryo images. > > My question is whether there is a program in ccp4 that will let you input a model and then generate a 2D projection using different plane groups. We are pretty sure, based on electron diffraction, that the 2D crystals contain a screw axis, as did the X-ray structure. Also, after generating the images, is there another program that will calculate structure factors and a diffraction pattern? Thanks in advance for the help, > > Jeff Brodin