On Sep 17, 2008, at 10:14 PM, Leo O'Young wrote:
I am new to the list, I am wondering if it is possible to increase the geometry of the Hydrophobicity-Surface models.
Thanks, Leo
Hi Leo, Welcome! The "hydrophobicity" in the preset is just a coloring scheme, so I will set that aside and discuss molecular surfaces. I am not sure what you mean by "increase the geometry." There are several ways you can adjust molecular surfaces in Chimera: change vertex density, probe radius, and also the radii of the underlying atoms. It is a molecular surface by the Richards definition, also known as the solvent-excluded surface, made of probe contact and re- entrant patches; it shows the VDW surface of the structure except with crevices smoothed. Currently Chimera does not show the solvent- accessible surface, which is where the probe center goes. <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/representation.html#surfaces
If you mean you want to make the surface "bigger" to enclose a greater volume, that can be done by increasing the VDW radii of the atoms, and to a lesser extent, increasing the probe radius, which will smooth the crevices more. One way to increase VDW radii is with a command; this would increase all radii by 0.7 A, for example: vdwdefine +0.7 (the command ~vdwdefine changes the radii back to defaults). <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/vdwrad.html> <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/vdwrad.html#changing
To change probe radius or other parameters of an existing molecular surface: - Ctrl-click the surface to select it - open the Selection Inspector (click the greenish button on the lower right corner of the Chimera window or choose Actions... Inspect from the menu) - in that dialog, Inspect "MSMS surface", and then edit the various parameters as desired <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/inspection.html#msmsprop
You can also set preferences to use different parameters for surfaces created in the future, so you don't have to change each one after you create it. To do that, choose Favorites... Preferences, go to the New Surfaces category, change parameters as desired and click Save. That only pertains to surface parameters, not VDW radii of atoms, however. <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/preferences.html#New%20Surfa...
I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html