POPC @ 310K, 450 mM of CaCl_2. Charmm36 with ECC-scaled ions

Simulations of a POPC bilayer with 450 mM of CaCl_2. 
The goal was to study the effect of salt on the order 
parameters of the lipid head group and the glycerol 
backbone for the NMRlipids project, see 
http://nmrlipids.blogspot.fi for more information.

A POPC bilayer consisting of 200 lipids (100 per leaflet) 
is simulated in the presence of 450 mM CaCl_2. The Charmm36 
model is employed for lipids, the Charmm compatible variant 
of the tip3p model for water, and the recent ion parameters 
by Kohagen et al. [2] for CaCl_2.

The Charmm36 force field parameters were obtained from
CHARMM-GUI [3] at http://www.charmm-gui.org

The ion parameters are available at
https://bitbucket.org/hseara/ions/

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The files are in GROMACS format. Trajectory (.xtc) is 
100 ns long with data saved every 100 ps. These data
were collected once the adsorption and desorption of 
CaCl_2 to the surface has reached equilibrium, namely
after 700 ns of simulation. Additionally, the initial 
structure (.gro), topology (.top), index file (.ndx), 
simulation paremeter file (.mdp), binary run input file 
for GROMACS v. 5.0–> (.tpr) and the energy output file 
(.edr) are provided. 

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[1] Update of the CHARMM All-Atom Additive Force Field 
for Lipids: Validation on Six Lipid Types
Jeffery B. Klauda, Richard M. Venable, J. Alfredo Freites, 
Joseph W. O’Connor, Douglas J. Tobias, Carlos Mondragon-Ramirez, 
Igor Vorobyov, Alexander D. MacKerell, Jr., and Richard W. Pastor
The Journal of Physical Chemistry B 2010 114 (23), 7830-7843
DOI: 10.1021/jp101759q

[2] Accurate Description of Calcium Solvation in Concentrated Aqueous Solutions
Miriam Kohagen, Philip E. Mason, and Pavel Jungwirth
The Journal of Physical Chemistry B 2014 118 (28), 7902-7909
DOI: 10.1021/jp5005693

[3] CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, 
and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field
Jumin Lee, Xi Cheng, Jason M. Swails, Min Sun Yeom, Peter K. Eastman, 
Justin A. Lemkul, Shuai Wei, Joshua Buckner, Jong Cheol Jeong, Yifei Qi, 
Sunhwan Jo, Vijay S. Pande, David A. Case, Charles L. Brooks, III, 
Alexander D. MacKerell, Jr., Jeffery B. Klauda, and Wonpil Im
Journal of Chemical Theory and Computation 2016 12 (1), 405-413
DOI: 10.1021/acs.jctc.5b00935