I currently store my 10 mg/mL mixed composition of POPC+PGPC (9:1 mol/mol) in a chloroform/methanol (9:1, v/v) solution. For the BLM experiment I require a working volume of ~40-50 uL of this solution which I dry into a lipid film and subsequently re-suspend in organic solvents. I use a decane : butyl alcohol mix for plain POPC, but I am having trouble with stabilizing my POPC+PGPC due to PGPC's highly oxidized nature.
So far I have tried (v/v) 50:1, 20:1, 10:1, 5:1, and 3:1 ratios of decane to butyl alcohol, and in each case my lipid precipitated into a milky substance from between 30 minutes to 1.5 hours.
I would greatly appreciate it if someone had any insight into how I could stabilize my lipids in organic solvent for an entire day? No papers on supported lipid bilayers/BLM have insight into working with oxidized lipids.
Thank you, in advance.
Yousuf O. Ramahi
Consider adding tocopherols lipid oxidation inhibitors to the mix if it doesn't interfere with your problem.
Yuri Mirgorod Thank you for your suggestion. Because PGPC is already heavily oxidized I don't think that will reduce the problem. Additionally including tocopherols may influence the membrane's physicochemical properties, which I need to control.
Michal Surma
Thank you for your suggestion, as well. I think you may be correct in suggesting that the issue is one of solubility. Actually, I just found out that the POPC stock I was using was old, and that may have further contributed to the instability. Once I am able I will try again with fresh POPC and PGPC. If that fails then I will try to make solutions with hexane instead of decane, as you allude to.
@Yuri Mirgorod @Michal Surma
Hello, again;
I thought I would update you. It turns out that the POPC we had ordered was faulty (old, or manufacturing error). We purchased new POPC and my lipids stayed in solution.
It is worth noting that I have had much better results when ordering lipids that are pre-dissolved in chloroform, rather than opening the ampule and adding chloroform once they arrive in the lab.
Thank you for your input, again.
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