Advanced starters guide
This walkthrough uses a small size example based on a real tomogram to covers several tasks.
The example data set
The data is a fraction of a tomogram. The full tomogram was used in "Cryo-electron tomography reveals novel features of a viral RNA replication compartment." (Ertel et al.), and represents several FHV viruses docked in the membrane of a mythocondrion.
In principle, you can download all the files related to this example with the command:
If it fails under Matlab or the Dynamo command line, you can try to directly use the linux order
This should have created the file called crop.rec in your current directory.
Size check of a file
You're probably curious to see what's inside, so that let's write first:
to let Dynamo check the dimensions of the file. The header of a .rec file is readed as a regular mrc, yielding:
filetype: volume size: 1285 x 956 x 786
So, it's a tomogram.
We can inspect quickly its contents with
dtmshow -otf crop.rec
Hereby, the flag -otf means "on the fly", telling dtmshow to not preload the full tomogram, but to access in disk the individual slices that are needed when inspecting a particular area.
Go up and down. We want to select the locations were the vesicles intersect the mythocondrion membrane and average them together. For this, we need to catalogue the tomogram, so that our annotations are stored with a clear relationship with the tomogram.
Cataloguing the tomogram
We can create catalogues just to contain a single tomogram. They are useful to keep track of all annotations, and of the typical transforms (binning, cropping of fractions) that we usually perform on a larged size tomogram of interest. In this case, we can create the catalogue directly from the command line:
>dcm -c create fhv
where dcm is the short form of dynamo_catalogue_manager and fhv is just an arbitrary name. The just created catalogue is empty, and we can add our tomogram with:
dcm -c fhv -at crop.rec
We can check that the tomogram is in the catalogue by asking Dynamo to show the contents of the catalogue
dcm -c fhv -l tomograms
dcm -c fhv -l t
The flag -l asks Dynamo to list items of a given category of catalogue contents, in this case tomograms
Prebinning the tomograms
We typically want to prebin the tomogram, i.e., have a version of smaller size that is known to the catalogue. This version will be useful in some operations that require a full tomogram in memory, an operation that can consume much memory and need a long time. In this example, this is probably not necessary: a tomogram with a sidelength on x and y of ~1000 pixels shouldn't pose any visualization problem. Still, in the command line, we can write
dynamo_catalogue_bin('fhv', 1, 'zchunk', 300);
where the parameter zchunk represents the maximum number of z slices that are kept simultaneously in the memory during the binning process. This parameter might be important for larger size tomograms.
Operation with GUI
These steps could have been performed thorugh the dcm GUI <tbi>
Annotation of particle positions
Now we can open the tomogram through the catalogue:
dtmslice crop.rec -c fhv -prebinned 1
Probably you don't like the initial contrast, change it with the button in the toolbar.