currently im working on biotinylated liposomes for this purpose i need to use biotin but since i have it only in 10 mg , hence i want to make a stock of it to use it later too. The paper im following says to use 0.01 molar ratio or 0.1 % of biotin.But i do not know how to make stock and how to make this molar ratio for it can any one please help me in this.
Shall be very thankfull for such favor.
Regards
Mehral Aslam
Dear Mehral Aslam ,
You first start with the molecular weight of DSPE-PEG(2000) Biotin. According to:
https://avantilipids.com/product/880129
It is 3014.867 g/mol.
So 3014.867 g/L corresponds to 1 mol/L or 1 M. This is equal to 3014.867 mg/mL. Let say you make a 0.001 M (which is of course 1 mM) solution you need 3,015 mg/mL.
The remark in the paper about 0.01 molar ratio means you add your biotin labelled lipid in a 100 fold dilution in relation to the other (not labelled) phospholipids. Let say the phospholipid mixture is 1 mM you add 10 μL of your stock to 1 mL of the phospholipid mixture.
PS. The remark 0.1% biotin is somewhat mysterious it only makes sense if they mean 0.1 volume%. Since this would mean a 1000 fold dilution once mixed with the phospholipid mixture.
Hope this helps.
Best regards.
Rob Keller
Dear Rob,
what if i need 0.1 mole percent biotin? what shall i have to do in this case ?
how to calculate the mole percent of biotin to add in lets say 10 ml of the organic solvent (methanol:chloroform)with PC and CH in it?
thankyou for your answer i am following it and i really do hope to get good results
Thanks
Regards,
Mehral Aslam
Dear Mehral Aslam ,
Thanks for sending me some additional info. One of the papers (you named biotinlimolratio) is somewhat sloppy in using %, molar ratio etc. But in the end both papers mean either 0.1 mol% or 1 mol% biotin labelled lipid.
The term 1 mol % means that 1 out of the 100 lipids are labelled lipid, which is used because of the rational ‘enough label to measure an effect and not more than necessary because of potential disruptive effects because of the introduction of a label (‘unnatural’) element. Of course 0.1 mol% gives potentially even less chance of unwanted side-effects.
Anyway, the mentioned 0.1 mol% means a molar ratio of 1:1000 of biotin labelled lipid to unlabelled lipid. The paper (you named b2) mentioned a lipid mixture of 2 mg/mL once in buffer. Let say you make a 100 mL solution of lipid and cholesterol (let say 2.5 mol%) in chloroform using this amount (2 mg/mL) as well:
-For this you use 100 x 2 mg lipid = 200 mg. According to:
https://avantilipids.com/product/850375
The molecular weight is 785.593 g/mol which is of course similar to 785.593 mg/mmol. So 200 mg DOPC corresponds to: 200/785.593 = 0.255 mmol.
-2.5 % of 0.255 mmol = 0.006375 mmol. This corresponds to 0.006375 x 386.65 = 2,46 mg cholesterol. Using mw of cholesterol, see:
https://en.wikipedia.org/wiki/Cholesterol
-0.1 mol% DSPE-PEG(2000)biotin means 0.1 % of 0.255 mmol = 0.000255 mmol. This corresponds to 0.000255 x 3014.867 = 0.0777 mg.
PS. This is very small but the ‘trick’ is to solve 7.77 mg in 100 mL chloroform (or 1 mg in 12, 87 mL) and then add 1 mL to the lipid solution.
-According to the procedure evaporate the chloroform and add 100 mL buffer to get the mentioned 2 mg/mL concentration of lipid suspension.
Hope this clarifies things.
Good luck with your research and best regards.
PS. The other paper (biotinlimolratio) you send used another biotin lipid without PEG! Here the biotin and PEG labelled lipid are two different lipids. They as well used 0.1 and 1 mol% biotin labelled lipid and talk about a molar ratio of Lipid/Cholesterol/Bx-lipid of either 54/44/1 or 54.9/44,9/0.1 molar ratio.
Rob Keller
Dear Rob,
Thank you so very much.
I will follow your guidance and i hope to get good results
Regards
Mehral Aslam
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