<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Hi Ernesto,<div class="">Sorry, there is no option to make a helix tube fit the residues more closely; it just makes one smooth arc per helix (no “S” or “J” shapes, only “C”), with no user control over the radius of curvature. I’ve also had these issues with certain structures.</div><div class=""><br class=""></div><div class="">However, these approaches might help:</div><div class=""><br class=""></div><div class="">(1) try breaking a long helix into two or more shorter helices.</div><div class="">(2) make tube radius fatter if the problem is certain sidechains far from tube</div><div class=""><br class=""></div><div class="">Details. (1) For example, this is part of chain C in 5gmk, with a very long S-shaped helix:</div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="939D33E9-09B2-4285-9792-261457EE92ED" src="cid:24C7680C-E044-4493-97EA-100559E94DC0@gateway.sonic.net" class=""></div><div class=""><br class=""></div><div class="">Then if I put the mouse over the structure I can see that the middle of the S shape is approximately residue 532 in chain C. I can break the helix by changing the type of that residue to non-helix, command:</div><div class="">setattr /c:532 res is_helix false</div><div class=""><br class=""></div><div class="">Then it fits better</div><div class=""><img apple-inline="yes" id="7BC90727-94BC-4B33-B606-C610B6369388" src="cid:58FE9C20-A187-4FBD-9931-DBAB07A90A4A@gateway.sonic.net" class=""><img apple-inline="yes" id="765E3569-39C2-483A-AB9D-ED1D8B749D48" src="cid:812D8D89-D67B-41C9-B740-D000479B18F1@gateway.sonic.net" class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">(2) Depending on the situation, however, the other approach of just making the tube fatter might work, e.g. command: cartoon style radius 4</div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="98C0D558-53CA-48B7-A3D5-C9803D25F611" src="cid:A1898148-B93E-414E-AC63-1316D199DC5B@gateway.sonic.net" class=""></div><div class=""><br class=""></div><div class="">I hope this helps,</div><div class="">Elaine<br class=""><div class="">-----<br class="">Elaine C. Meng, Ph.D. <br class="">UCSF Chimera(X) team<br class="">Department of Pharmaceutical Chemistry<br class="">University of California, San Francisco<br class=""></div><br class=""><blockquote type="cite" class="">On Oct 1, 2019, at 2:50 AM, Ernesto Arias Palomo <<a href="mailto:earias@cib.csic.es" class="">earias@cib.csic.es</a>> wrote:<br class=""><br class="">Good morning,<br class="">We are using the modeHelix tube to represent the secondary structure. However, our structure contains some long and curved helices, and the representation does not follow their shape with enough precision. Is there any option to increase the fit of the tube to the overall shape of long helices?<br class="">Thank you very much for your help.<br class="">Kind regards,<br class="">Ernesto.<br class=""></blockquote></div></body></html>