Sarah Witzke wrote:
Dear gmx users,
I am sorry to ask this question again, but reading in the email achieve did not
enlighten me. I found this email which describes my problem, but unfortunately
it has no replies:
http://lists.gromacs.org/pipermail/gmx-users/2008-July/034950.html
Also there are these two recently emails:
http://lists.gromacs.org/pipermail/gmx-users/2010-January/047767.html
<http://lists.gromacs.org/pipermail/gmx-users/2010-January/047767.html> , but I
am still in doubt.
So my question is regarding the unsaturated lipid chain of POPC. I would like
to calculate the order parameters for my united atoms so I make first an index
file with the tail atoms from the carbonyl-C to the methyl-C and then I run
g_order -od. Then I make a new index file with the two atoms of the double bond
and the atom before and after the double bond (four atoms in total) running
g_order -unsat -od
I then take the two values from the last g_order run and replace them with the
order parameters for the double bond calculated without -unsat. When looking at
the graph and comparing to the literature this graph it looks wrong: First
there is a small dip in the order for the atom before the double bond, then it
goes a bit up for the first double bonded C, and then for the next double
bonded C and the atom after that the order is quite low. I know this
description is not good, but it was just to explain, that the graph is not as
expected.
I would very much appreciated if anyone could tell me, where I go wrong.
I don't see why a drop in the order parameter is unexpected. I see it all the
time in published papers of unsaturated lipids, for example:
http://pubs.acs.org/doi/abs/10.1021/jp902131b
http://www3.interscience.wiley.com/journal/114209721/abstract
-Justin
Thank you,
Sarah
--
========================================
Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
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