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Mar 20, 2019 at 10:43 history edited Reto Höhener CC BY-SA 4.0
typo
Dec 22, 2015 at 6:39 comment added Greg I think your problem is the difference between the chemist and physicist notation of dipoles / polarization: they use opposite definition, and most of them not aware. So there might be big mix-ups in the references, if you are not careful.
Dec 22, 2015 at 4:52 answer added Martin - マーチン timeline score: 14
S Jul 6, 2015 at 20:58 history bounty ended CommunityBot
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S Jul 4, 2015 at 15:10 history suggested WYSIWYG
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Jul 4, 2015 at 14:24 review Suggested edits
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Jul 2, 2015 at 0:59 comment added user3786990 scienceline.ucsb.edu/getkey.php?key=2477
Jun 30, 2015 at 11:21 comment added WYSIWYG @Loong You can add that as an answer and you can claim the bounty too (a petty 50 points, but I don't have much to spare here)
Jun 29, 2015 at 15:08 comment added user7951 av8n.com/physics/electric-dipole.htm#sec-mutations
Jun 28, 2015 at 19:47 history tweeted twitter.com/#!/StackChemistry/status/615245172956364800
S Jun 28, 2015 at 18:59 history bounty started WYSIWYG
S Jun 28, 2015 at 18:59 history notice added WYSIWYG Canonical answer required
Jun 27, 2015 at 9:12 answer added Jan Jensen timeline score: 8
Jun 27, 2015 at 6:11 history migrated from biology.stackexchange.com (revisions)
Jun 23, 2015 at 12:32 comment added WYSIWYG @Zalumon Electrical dipole moment is always negative to positive. See here. I am not sure why in chemistry a reversed direction is used for molecules. Perhaps because they want to denote the direction of electron cloud density. This seems to be a case of conflict of semantics. It is better to ask this question in Chemistry-SE.
Jun 23, 2015 at 9:57 comment added Reto Höhener @WYSIWYG thanks. my question is: why do people draw the macro/net/sum dipole of a linear alpha helix from negative to positive, but for a water molecule they draw it from positive to negative.
Jun 23, 2015 at 3:43 comment added WYSIWYG Dipole moment is a vector. The molecular dipole moment that you are talking about is the net dipole moment i.e. sum (vector addition) of all bond dipole moments. Like all vectors, dipole moment has direction. When you say there is a dipole moment from C-terminus to N-terminus you are thinking of protein as a linear molecule, ignoring the tertiary structure. The net dipole moment of the protein will depend on the tertiary structure and the side chains. If this comment necessarily answers your question then I'll convert it as answer.
Jun 22, 2015 at 21:38 comment added canadianer The direction of the arrow is just a convention. Apparently no hard rule exists for denoting the dipole moment of alpha helices. What is important is that you know that the C-terminus is partially negative and the N-terminus is partially positive. I guess it's also important to know which way your teacher wants the arrow drawn.
Jun 22, 2015 at 20:50 comment added Reto Höhener The more "alpha helix dipole" google images I look at, the more confused I get. Everybody seems to have a different idea. And wikipedia says that there is some controversy about the alpha helix macro dipole, but doesn't give a direction.
Jun 22, 2015 at 20:43 comment added Reto Höhener The images were just the first that came up when googling for "molecular dipole" and "alpha helix dipole". We have this exercise where something about alpha helix stability is argued with the helix macro dipole.
Jun 22, 2015 at 20:31 comment added James The O to H in the backbone will be massively irrelevant compared to polar or charged amino acids, or non-polar (hydrophobic) residue r groups. In structural biology you don't worry about the backbone charge direction as it will not affect the iso/leucine and polar groups that form the "surface" of the helix. I guess this question is confusing without any context. Could you cite the origin of the images?
Jun 22, 2015 at 20:23 comment added Reto Höhener Any alpha helix I guess.
Jun 22, 2015 at 20:19 comment added James Are you talking about alpha helices in membranes or in protein cores? Either way it has been a while since the polarity was described as going from C to N.
Jun 22, 2015 at 20:03 history asked Reto Höhener CC BY-SA 3.0