I got the peptide solution (dissolved in sterile distilled water) in a concentration of 5 mg/ml from another lab and keep it in -80C. I want to dilute it into 100 ug/ml but I don't know which one is a better vehicle for extending peptide's shelf life between basal cell culture media or 1x PBS. Are there any differences between them? Another question is that, is synthetic peptide sterile? Should I need to add some more antibiotic in the diluent? I don't want to filtered the peptide solution, in order to avoid yield losing.
Thanks in advance
I dilute my peptides in sterile DMSO and keep small aliquotes at -20C, any other solution would not preserve the peptide integrity and sterility for long. I defreeze and refreeze the same aliquote up to 2-3 times with no loss of peptide integrity.
It really depends on your downstream application. You can prevent microbial growth by addition of sodium azide (poison) to a final concentration of 0.02%. Of course adding this to cells would not be a good idea, but would be compatible with in vitro assays. Storing frozen will also prevent microbial issues, but it is best to freeze aliquots so as to avoid problems with repeated freeze-thaw cycles. In general proteins (and perhaps peptides) are more stable in the presence of counter-ions provided by some salt (like PBS) than in pure water.
Dear Nithipong, There's a nice guide from Bachem in which they answer most questions you might have about handling of peptides, you can find it in the attached link. Regarding your specific question:
Dissolved peptides are less stable than the lyophilizates. The solutions are best aliquoted before freezing to avoid thawing-refreezing cycles stressing the peptide. Solution stability depends on the type of solvent and the pH (pH 5-7 is considered as optimum). Peptides containing Asn, Gln, Cys, Met, Trp, Tyr tend to be less stable. Stock solutions of peptide substrates are best prepared in dry organic solvents to avoid premature hydrolysis. The stability of the aliquots may range from weeks to months.
We've used peptide solutions with cell cultures many times without any sterilization, although our experiments are typically very short (few hours tops) and bacterial contamination wouldn't be a problem.
http://www.bachem.com/service-support/faq/handling-of-peptides/
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