Hi, What do you mean by difficulties of creating surfaces? I speak for a person coming from the cryo-em world, that T4 RNAP surface pretty much looks like a 4A 3D reconstruction based on cryo-EM data. Compare with Ludtke's GroEL structure at about 4 A (Ludtke et al., 2008, Structure 16:441-448). Maybe compare with surface renderings of the 4A X-ray structure of holoenzyme by Murakami (Science, 2002) or the first x-Ray structure of RNAP2 at ~5A by Darst? I am sure that the Chimera team will tell you more about how the surface is calculated, but it looks correct to me. Sincerely, - S ------------------------------------------ Sacha De Carlo, Asst. Professor Marshak Building Room 1335 The City College of NY (212) 650-6070/6582 E-mail: sdecarlo@ccny.cuny.edu http://www.planetesacha.com/Work.htm ------------------------------------------