[gmx-users] Question about analysing micelle structure

[Alif M Latif]

Greetings GROMACS users and developers,

I've been studying about the structure of a nanoemulsion of palm-oil and surfactant in water. Many simulations have been performed. My first objective is to replicate the experimental work done and then study the structural properties. I'm using GROMACS (its free, flexible, and fast!!). Simulations produced convincing results; at low composition=no micelle formation, 30% lipid=cylindrical micelle, higher % = two phase (bilayer-like). 

Its all going the right way until I changed the surfactant with higher HLB value which, (Israelachivli, 2005) theoretically tend to produce spherical micelle. I'm still getting cylindrical, I did simulation with only surfactant and water, (assuming the long-chained oil structure was the culprit). Both surfactants (higher and lower HLV value) still produced cylindrical micelle. My questions are: 

--Is this got anything to do with my parameters? (in .mdp file?) 

--Misconcept? Do i need to prepare spherical micelle as the initial structure and then run MD? right now my initial molecules scattered aroung the   simulation box randomly.

--Can longer simulation time produce spherical? (I've already did 10 ns)

I'm pretty confident about the composition of oil and surfactant (experimental data). Could anyone suggest better way? Valid way to do this.. I'm short of experience and no one had done this before right here. Sorry for the long mail. I need help. Thank you very much for reading. Advices, comments and suggestions are greatly welcomed.

Thanks again,

Alif (Msc. Student)
Chemistry Department,
Faculty of Science, Universiti Putra Malaysia.
Serdang, Selangor, Malaysia.


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