Here are some lesser-known PyMOL tricks that let you do some pretty cool (and useful) things:
1. Display B-factors
If you want to see the “b-factor putty” view where the backbone is displayed as a tube with a diameter correlated to the b-factor of the structure, simply click the Action button of the object (the “A” button); mouse to “preset”; and select “b-factor putty.” The structure will automatically convert to a colored putty view suitable for slide figures or publications.
2. Poisson-Boltzmann electrostatics
Want to get a sense for the patches of positive and negative potential on the surface of your protein? No need for esoteric PB electrostatics solvers (at least at first!); PyMOL has got you covered. Click on the “action” button as before, but this time select “generate” and then “vacuum electrostatics.” Finally select “protein contact potential (local).”
Be sure to heed (or, more typically, ignore) the warning about how the results are qualitative and not quantitative. And then proceed to enjoy the lovely patches of negative and positive potential rendered on the surface of your protein of interest.
3. Quickly get an estimate of the solvent-accessible surface area (SASA) of a PDB structure
This takes advantage of the “get_area” command in PyMol. You’ll have to dive into the command line here to take advantage of this trick. For example, if you have a PDB object 1UBQ (ubiquitin) you would do the following at the command prompt (the bar below the structure viewing area):
set dot_solvent, 1 ## set dot_solvent to calculate the SASA
set dot_density, 4 ## most dots for most accurate calculation
get_area, 1UBQ ## calculate the SASA
Keep in mind that as in point #2, the SASA calculation in PyMOL is an estimate. For very accurate calculation, use a dedicated SASA solver.
4. Render a scene as a pen-and-ink sketch
This tip is a lot of fun, because it lets you see your molecules as if they had been drawn in a pen-and-ink manner, like a real cartoon. This is sometimes useful for presentations or other less-formal venues where you want to clearly illustrate something about your molecular structure.
Once again, we will use the command prompt. Start off by typing:
set ray_trace_mode, 3
PyMOL will render your scene and display the result. Here is what it looks like for 1UBQ:
5. “Rock” and roll
Finally, the last tip is extremely simple. If you and your colleagues are sitting around looking at a molecule structure, sometimes it helps to view it from different angles. Instead of twiddling the mouse back and forth, you can simply click the “rock” button at the top right of the PyMOL window to start the scene panning gently from side-to-side to aid visualization.
Please feel free to post any other useful PyMOL tricks and tips in the comments below.
Note: I am running PyMOL 1.3 Incentive on a Mac OS X 10.6.8 system.