Reference
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Factual reference for working with research peptides — nomenclature, lyophilization and solubility, reconstitution, storage and aseptic handling, purity by RP-HPLC and ESI-MS, and the analytical documentation that ships with each lot. Specifications and methodology only; supplied for laboratory research use.
Methodology
Reconstituting lyophilized peptides
How to reconstitute a lyophilized (lyophilized) research peptide: choosing a diluent, working out mg/mL from net content, swirling rather than shaking, 0.22 µm filtration, septum handling, and storing the solution.
Storing research peptides
How to store research peptides: the dry condition on the vial label (−20 °C for most, 2–8 °C for some) for the lyophilized (lyophilized) powder, 2–8 °C or frozen aliquots after reconstitution, the degradation route each control addresses, and what a retest date asserts.
Aseptic technique for laboratory handling
Aseptic technique for laboratory handling of research peptides: disinfecting the work area, swabbing a septum and avoiding coring, 0.22 µm sterile filtration and what it retains, one-pass aliquoting into sterile labware, and what belongs on the label.
Analysis
How to read a Certificate of Analysis
How to read a peptide Certificate of Analysis field by field: identity by ESI-MS, purity by RP-HPLC area percent at 220 nm, net content, water content by Karl Fischer, counter-ion content, appearance, the retest date, and matching the lot to your vial.
Peptide purity: RP-HPLC and ESI-MS
What a peptide purity percentage means: how RP-HPLC computes area percent at 220 nm, how to read a chromatogram, why two vendors' purity figures are not comparable, how ESI-MS charge-state envelopes establish identity, and what area percent cannot see.
Fundamentals
Peptide nomenclature and how to read a sequence
How to read a peptide sequence: the one-letter and three-letter codes for all twenty standard residues, N-terminus to C-terminus reading direction and residue numbering, the Ac- and -NH2 terminal modifications, cyclic and disulfide notation, non-standard residues, and two catalog sequences read field by field.
Lyophilization: what freeze-drying does to a peptide
What a lyophilized (lyophilized) peptide is: freezing, primary drying by sublimation and secondary drying for bound water, why the cake is the void structure the ice left, puck, film and powder forms, mannitol and trehalose as bulking agents, collapse and meltback, and residual moisture by Karl Fischer.
Peptide solubility and solvent choice
What solvent to use for a research peptide: what net charge, hydrophobicity, length and secondary structure decide, counting charged residues at neutral pH to get a net charge, trying water first at small scale, acetic acid, ammonium bicarbonate and DMSO as co-solvents, minimum solubility at the isoelectric point, and telling aggregation from insolubility.