Glossary
- Lyophilised
- Freeze-dried. Water is removed under vacuum from a frozen solution, leaving a dry cake or powder considerably more stable than the same material in solution.
- Reconstitution
- Returning lyophilised material to solution by adding a solvent.
- HPLC
- High-performance liquid chromatography. Separates the components of a mixture so each can be quantified. Reported purity is the main peak as a percentage of total peak area.
- Mass spectrometry
- Measures the mass-to-charge ratio of ionised molecules, giving molecular weight. Used to confirm that the compound synthesised matches the compound intended.
- Chromatogram
- The output trace of a chromatographic run, showing detector response over time as separated components elute.
- Net peptide content
- The proportion of material in a vial that is peptide rather than counterion or residual water. Typically determined by amino-acid analysis.
- Counterion
- The ion paired with the peptide in its salt form, commonly acetate or trifluoroacetate. Contributes mass without contributing peptide.
- Bacteriostatic water
- Sterile water containing a preservative, conventionally 0.9% benzyl alcohol, which inhibits microbial growth and so permits more than one withdrawal from a vial.
- Endotoxin
- Bacterial cell-wall fragments that survive sterilisation and can confound biological assays. Screened for separately from purity.
- Sequence
- The order of amino-acid residues in the chain, written in one-letter or three-letter code. The sequence defines the molecule; two preparations sharing a name but not a sequence are not the same substance.
- Fragment
- A defined portion of a larger protein rather than the whole. A fragment behaves differently from its parent protein and should not be described interchangeably with it.
- Aggregation
- Association of peptide molecules with one another, often coming out of solution. Promoted by shaking, foaming and repeated freeze-thaw cycling.
- Hydrolysis
- Cleavage of peptide bonds by water. The principal reason material is supplied and stored dry.
- Aliquot
- A measured portion divided off from a larger volume, so the remainder is not disturbed.
- Lot / batch number
- The identifier tying a specific vial to a specific synthesis and its certificate.
- RUO
- Research use only. The material is supplied as a laboratory reagent, not as a drug, supplement, food or cosmetic, and not for human or animal consumption.
Units and conversions
| Quantity | Equivalent | Note |
|---|---|---|
| 1 mg | 1,000 mcg | The conversion behind most order-of-magnitude errors |
| 1 g | 1,000 mg | |
| 1 mL | 1 cc | Used interchangeably on syringe barrels |
| 1 mL | 100 units on a U-100 syringe | U-100 graduations are insulin units, not millilitres |
| 10 units (U-100) | 0.1 mL | |
| 1 IU | Compound-specific | An international unit measures biological activity, not mass, and does not convert to milligrams by any general rule |
On international units. IU is defined separately for each substance by reference to a biological standard. There is no universal IU-to-milligram conversion, and applying one from a different compound produces a meaningless number.
General references
Sources used for the analytical and handling material in this reference. None are affiliated with this site, and none are suppliers.