Ribbons computation are based on the method developped by Carson et al. ref . By default it is a wireframe ribbon representation of five parallel strands, but you can change the number of strands to be used (up to 21) in the Ribbons Preferences. The number of strands to be used during the real time operations can also be changed independently.
If you want nicer images with solid ribbons, you will have to use POV-Ray or enable OpenGL (option 'Render in 3D' from the Display menu) and ensure that the 'Render as Solid Ribbon' option from the Prefs:Ribbons menu is enabled.
You can vary the width and height of the solid ribbon independently for helices (see difference between Fig.1 and Fig.2), strands and coils; and you can add an arrow at the C-term position of helices and strands to show the direction of the chain. The width and height of this arrow is expressed in percentage of the ribbon width and height.
By default, the top and bottom faces color of the ribbon are taken from the ribbon color associated to each amino-acid. See the Control Panel section to know how to change the ribbon color for individual amino-acids.
In any case, you can bypass those individual colors and provide a color to be used for all top, bottom or side faces by enabling the corresponding checkbox and clicking on the associated Color Button of the dialog. For example,default helices and strands sides colors are grey (as shown in Fig.1).
Finally, the shape of the helices, strands and coils can be independently choosed among four possibilities (rectangle, ovoid, top-flat-ovoid or bottom-fat-ovoid). The possibility to define custom shapes will be added later.
|Fig.1 Default settings, with helices and strands sides in grey.|
|Fig.2 Height and witdth of strands has been increased while helices width and height have been set equal to the one defined for coils. Side of helices is no longer grey.|
|Fig.3 Arrows have been removed, and the ribbon has now the same width for helices, stands and coils. The default gray side color has been disabled, and an ovoid shape has been selected for all structures.|
|Fig. 3b Same as before but rendered with a metallic texture in POV-Ray.|