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Unformatted text preview: THE HELIX HANDOUT by Frank Deis Most people have trouble remembering the difference between a right-handed helix and a left-handed helix. Since helices crop up in biochemistry, here are some hints for keeping them straight in your head. The first concept you need is that helices continue to look the same when you turn them upside down. You can't turn a right-handed helix into a left-handed helix just by inverting it, you have to untwist it and sart over. An easy way to classify helices is by looking at the direction the visible fibers run when the helix is vertical. They will either go up to the right or up to the left. If they go up to the right, the helix could be called a "Z- twist" helix, because the vertical stroke of the letter Z goes up to the right. "Z-twist" helices are right-handed. Notice that a "Z" looks the same when turned upside down, just like a helix. The other possible form of helix would have fibers which go up to the left, like the vertical stroke of the letter "S". Thus, left-handed helices would have fibers which go up to the left, like the vertical stroke of the letter "S"....
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- Spring '11