Microsoft Excel and a hazy recollection of O-Level trigonometry. As you know, DNAĬan adopt a variety of structures: A, B, Z (but crucially, they areĬoordinates of blocks were calculated by Andy Bates, using It explains why helical structures are so common. Molecular explanation of the actual conformation of DNA, but Simple model presented here is a not a substitute for this sort of Of course, the actual shape of DNA is determined by the allowedīond angles in the sugar-phosphate backbone, the way the hydrophobicīases stack together and the interaction between the two strands. The molecule, for repeated additions of nucleotide not to formĪ helical structure. Relationship of one nucleotide to the next, given the asymmetry of It would actually be difficult to arrange the Think of it as an asymmetric block, as before. OfĬourse, to make a double helix, we can simply fill in the other Realistic) rules about the way monomers (blocks) stack together. So, it's really fairly easy to form a helix given some simple (and If we now continue to add blocks with the same Hereīut this time the second block stacks onto it with a Is very likely to be some asymmetry in the way the blocks stack. Will stack on top of each other in a regular face to face way. We can model this in a simple way by considering aĬauses the stack to curve around, in this case intoīut, there is no reason why the building blocks (monomers) General chiral, asymmetric, molecules, not regular rectangularīlocks. However, the building blocks of macromolecules are in Surprised to see a simple stack of blocks! , with each block having the same relationship to the previous one.
You can rotate the structure in the left-hand window at any time. If you have rotated it, then click to reset it to its original The amino acids of a protein) as building blocks. We can address this question by simplifying the situation.Ĭonsider the repeating units of a polymer (the nucleotides of DNA or
So the question above might be recast as: Why are helices so common in macromolecules? Have a characteristic left-handed helical The triple helix of poly proline-glycine helices in.The helix of protein subunits in tobacco mosaic virus,.Helices are actually extremely common in macromolecules - the obvious example is the Structure, you can rotate it around at will. This tutorial uses a utility called Jmol, which allows us General response to the stacking up of single monomer units into a In fact, as this short tutorial aims to show you, the helix is a Solution to the problem of the replication of DNA - how to make twoĮxact copies from one original - but why is DNA helical? Many people perceive the double helical structure of DNA (left) toīe an extremely elegant, and in some ways miraculous structure.Ĭlearly, the presence of two complementary strands is an efficient
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