Microgram (mcg)
Definition
One millionth of a gram, written mcg or ug, with 1,000 of them to the milligram. Peptide quantities move between the two scales constantly, and a factor of a thousand is the easiest arithmetic error to make when reading a vial against a published protocol.
Terms used in this definition
Other entries this definition refers to.
What this means for research sourcing
Getting this right matters when preparing lyophilized research peptides for in vitro work. Volta ships compounds as lyophilized powder for reconstitution.
Related Terms in Preparation
Diluent
The liquid used to dissolve or further dilute a peptide. Buffered saline, dilute acetic acid and small fractions of organic solvent all appear in the literature, chosen for what the compound will dissolve in and what the assay will tolerate.
Buffer
A solution that resists pH change when acid or base is added. Peptide stability and solubility both track pH, so a buffered diluent keeps a preparation in a known state instead of a drifting one.
pH
The acidity of a solution on a logarithmic scale. It determines what charge a peptide carries, how soluble it is, and how fast deamidation and hydrolysis proceed, which makes it a stability variable rather than a detail.
Osmolarity
The total concentration of dissolved particles in a solution. Preparations used on living cells are matched to physiological osmolarity, because a hypotonic or hypertonic medium stresses the cells independently of whatever is being tested.
Lyophilization
Freeze-drying: the solution is frozen and the water removed by sublimation under vacuum, leaving a dry cake whose chemistry is far more stable than the solution it came from. Properly stored lyophilised peptide keeps for years at -20C.
Lyophilized
Freeze-dried. Research peptides ship in this form because a dry powder survives transport and storage that a solution does not, and it has to be reconstituted before any work can be done with it.
Aseptic Technique
The handling practices that keep a preparation from being contaminated: disinfecting a stopper before it is pierced, using a fresh needle, and not touching the parts of the equipment that meet the solution. It governs contamination, not sterility, which a container either had or did not.
Vial
The sealed glass or plastic container a peptide is supplied in, closed with an elastomeric stopper under an aluminium crimp. A single-dose vial carries no preservative and is intended to be entered once; a multi-dose vial carries one so it can be entered repeatedly.