Dear Annaclaudia Burrelli ,

Not entirely sure why you need higher concentrations to start with. But more importantly have a good look at the terminology. According to:

Marsh, D. (2016). Equation of State for Phospholipid Self-Assembly. Biophysical journal, 110(1), 188-196.

above a certain chain length, you cannot speak of CMC since the lipid you talk about form a bilayer (see appendix in this paper). I suggest you have a look at the wealth of reference in this paper which certainly give ‘inspiration’ on how to set up your experiment. See for example:

Marsh, D. (2012). Thermodynamics of phospholipid self-assembly. Biophysical journal, 102(5), 1079-1087.

Best regards.

Dear Rob Keller ,

thanks for the answer. I've never worked with lipids before, I'm just a student working on her thesis. I want to study interaction between free lipids and proteins during protein fibrillation. But to weigh lipids for the preparation of my samples I will have high concentration of POPG and POPC and they will associate into MLV. I'm not sure of their behaviour after scalar dilutions. Will I obtain free lipids simply after the dilutions or they will remain associated in some vescicles? What can I do if they will still remain associated? I'm thinking on sonication but I can't find something on literature.

Dear Annaclaudia Burrelli ,

Well, I still advice you to check some papers in the link(s) I gave for ideas. Concerning your idea about sonication I am not sure; I know this will change MLVs into SUVs but whether it can change vesicles into free lipid I don't know at least not what exactly will happen at very low concentrations.

I think diluting your lipid solution (when dissolved in something like methanol or ethanol, use at least solutions miscible with water/buffer) will give free lipids and due to the dilution (let’s say a 100-fold) you do not have to worry about the trace amounts of solvent.

I have no personal experience with it but one of the links I suggested, seems to suggest that when you heat the lipid solution (after dilution of course) the equilibrium might shift from micelle/vesicle to free lipid. This will remain presumable a free lipid fraction if your concentration is low enough and after cooling down you can add your protein).

Unfortunately, I could not find a proper literature reference (so far) for this, but I think you come to a point to ‘just’ try.

Good luck and kind regards.