Features of Ribbon Diagrams
| Secondary Structure | ||
|---|---|---|
| α-Helices | Cylindrical spiral ribbons, with ribbon plane approximately following plane of peptides. | |
| β-Strand | Arrows with thickness, about one-quarter as thick as they are wide, shows direction and twist of the strand from amino to the carboxyl end. β-sheets are seen as unified, because neighboring strands twist in unison. | |
| Loops and miscellaneous | ||
| Nonrepetitive loops | Round ropes that are fatter in the foreground and thinner towards the back, following smoothed path of Cα trace. | |
| Junctions between loops and helices | Round rope that gradually flattens out into a thin helical ribbon. | |
| Other features | ||
| Polypeptide direction,
NH2 and COOH termini |
Small arrows on one or both of the termini or by letters. For β-strands, the direction of the arrow is sufficient. Today, the direction of the polypeptide chain is often indicated by a colour ramp. | |
| Disulfide bonds | Interlocked SS symbol or a zigzag, like a stylized lightning stroke | |
| Prosthetic groups or inhibitors | Stick figures, or ball&stick. | |
| Metals | Spheres (e.g., see top image). | |
| Shading and colour | Shading or colour adds dimensionality to the diagram. Generally, the features at the front are the strongest, while becoming lower in contrast towards the back (as in the triose P isomerase drawing above). |
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