Projecting 3D model

Input:

  • 3D model in .mrc format (e.g. input.mrc)

How to

To project for particle picking, you do not need many fews. Therefore, a coarse angular sampling is recommended, such as 20 or 30 degrees.

We will use RELION for projecting the 3D volume. But, before projecting, we will low-pass filter the model.

Log into any lab machine and type:

$ module load relion
$ relion_image_handler --i input.mrc --o input_lp.mrc --angpix 1 --lowpass=10
$ relion_project --i input_lp.mrc --o input_lp_proj --nr_uniform 10

This will output a stack of projects in .mrcs format and an accompanying .star file.

Converting into individual files for Appion

If you want to pick particles in Appion, you will need to create individual .mrc files for these projections.

To do this:

$ module load eman2
$ e2proc2d.py input_lp_proj.mrcs mrc  --unstacking

This will output a series of files named mrc-??.mrc that can be uploaded to Appion.