Yes. The major commercial peptide suppliers in the US advise .2 micron filtration can be used if sterilization of reconstituted solution is desired, which indicates, at least at that filter size, peptides of all lengths will pass. Protein adhesion varies between filter materials, so its worth checking to ensure your filter type isn't "high protein adhesion", few are though.
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Here's something very interesting I came across regarding peptide filtration.
"Protein aggregates", folded and clumped proteins. aka DIMER:
1: Can cause an immune response, leading to any number of side effects. Several peptide drug trials in the last few years failed due to immunogenicity. They detected an immune reaction and stopped the trial. It's now believed this was caused by dimer formed by #2
2: Chemicals leaching from the stopper coring fragments, and especially silicone, cause peptides to clump into aggregates, ie, dimer.
3: Peptide aggregates can be filtered out. Thereby avoiding potential side effects. Several proposals suggest "bedside filtration" of peptide based drugs just prior to injection for improved patient safety. and better outcomes from the compound.
This is from a peptide vial that appears clear to the naked eye.
Personally I find the potential to clear out defective, possibly side effect inducing, malformed protein lumps from reconstituted peptides, and improving their performance, a very exciting possibility. I'd love others to research this topic and see what they can come up with as well.
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