hello,
I have two peptides one is 11 AA and another is 15 AA long.
I got them delivered in powdered form.
Now I want to dissolve it. One is soluble in water and another is in DMSO.
But the problem is the company said: for long term storage, it is strongly recommended that you store peptide in powder form at -20°C, away from strong light, and under dry condition. Repeated freeze-thaw cycles
should be avoided. A peptide solution once prepared should be used as soon as possible. If storage in solution is unavoidable, use sterile buffers at pH 4-6 and store in aliquots at -20°C or lower to prolong the storage life.
I have got 5 mg of each peptide.
My questions are:
How can I weigh my peptide for dissolving in a sterile way?
What is the ph of DMSO solution? Which concentration should I use ?
If my peptide is soluble in water can I also use PBS to dissolve it?
I really need to know all these information very urgently.
Thanks in advance.
Simple answer, you can't. Depending on the application of the peptide, sterility most likely isn't a problem. I have never worried about sterility while making a peptide solution for my in vitro experiments. Just make sure to sterile filter your DMSO, water, or buffer before using it to make the peptide solution. DMSO is an aprotic solvent...so pH doesn't really apply. When I have dissolved my hydrophobic peptides in DMSO, the solution tends to have a pH between 6-8. If your peptide is soluble in water, then you can use PBS to make your solution.
Like Forest said it not that easy to do it in a sterile way, just sterile filter your solvents and use sterile plastic. Weighing out something like 1-2 mg of peptide is possible, remember to let the powdered peptide come to room temp, don't wear gloves because they sometimes cause static electricity that causes the freeze-dried powder to cling to the glove/tube/spatula. In my experience it is worth it to use weight a little more peptide for accuracy, then just freeze it in aliquots at -80 is probably better than -20.
Dissolve your peptide and divide in smaller fractions (for example 0.1 mg quantities) in separate vials. Freeze in liquid nitrogen and store at -80 °C. You can also opt for freeze drying the smaller fractions and store those in -20 °C. In which buffer you dissolve depends on what you are going to do afterwards with the peptides. Freezing the peptides dissolved in PBS by putting the sample in a -20 °C without freezing in liquid nitrogen might result in pH shift, buffer salts will freeze out.
Easy.
Dissolve your peptide in a buffer containing 50:50 MeCN:H20 that but itself will sterylize the solution. Be sure you use a container that is sterylized.
Lyophilize the sample on a sterylized container containing a filter to prevent any particles going inside your peptide when you break the vaccum. I wouldl recommend usign a 0.5 µm filter.
Voila! You have your peptide sterylized. We use it all the tim eto test our peptides in vivo (mice and rats).
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