Hello, I observed that Chimera (like almost all other protein viewers) aligns the ribbon of a helix in a way that the ribbon is parallel in every twist (the ribbon virtually forms a cylinder). My question is: is this correct, strictly speaking? I thought that the ribbon should lie in the plane defined by two successive C-alpha atoms and the associated O atom? (Mike Carson defines it that way in his "Ribbons", following the instructions of Richardson's "The anatomy and taxonomy of protein structure"). If you draw it that way, the ribbon forming the helix will tilt slightly outwards. Is the alignment of the helix ribbon in Chimera done simply because it looks better this way or is there another reason? I did some research on this topic via google and even asked a certified biologist (scientific assistant), but the internet had not much to say about it and the biologist only told me that cartoon drawings don't have to be very accurate, since they are only a tool to get a general idea of the protein's structure. Best regards, Michael Krone