Peptide Research Glossary

July 9, 2026

Peptide Research Glossary

This glossary defines terms that appear on research-supply labels, in lab notes, and in reconstitution math. Entries are definitions only. They describe chemistry, units, storage, and equipment, and nothing else. For the calculations that connect several of these terms, see the reconstitution and blend calculators.

Physical Form and Preparation

Lyophilized. Freeze-dried. Lyophilization is a process that removes water from a frozen material under vacuum, leaving a dry powder or cake. Many research peptides are supplied lyophilized because the dry form is more stable in transit and in long-term cold storage than a solution would be.

Reconstitution. The act of returning a lyophilized (dry) substance to liquid form by adding a measured volume of liquid. Reconstitution does not change the amount of peptide in the vial. It only disperses that fixed amount into a chosen volume of liquid.

Diluent. The liquid added to a dry substance during reconstitution, or added to an existing solution to lower its concentration. Common diluents referenced in peptide research include sterile water, sterile water for injection, bacteriostatic water, phosphate-buffered saline, and sterile saline. The diluent is the carrier, not the active material.

Water and Storage Terms

Bacteriostatic water. Sterile water that contains a small amount of a preservative, typically 0.9 percent benzyl alcohol. The prefix "bacteriostatic" means the additive slows or halts bacterial growth rather than killing all microbes outright. Because of the preservative, a reconstituted vial made with bacteriostatic water is generally described as having a longer usable window under refrigeration than one made with plain sterile water. Sterile water, by contrast, contains no preservative.

Aliquot. A measured portion divided out from a larger quantity. To aliquot is to split a solution into several smaller, separately stored containers. Researchers describe aliquoting as a way to reduce how often a single stock container is opened, since each portion can be handled on its own.

Amount Units: mcg, mg, and IU

mg (milligram). A unit of mass equal to one thousandth of a gram. Peptide quantity in a vial is commonly labeled in milligrams, for example 5 mg or 10 mg.

mcg (microgram). A unit of mass equal to one thousandth of a milligram. So 1 mg equals 1,000 mcg, and 0.5 mg equals 500 mcg. The symbol mcg is used in place of the Greek "µg" to avoid handwriting confusion.

IU (International Unit). A unit defined by biological activity rather than by mass. For substances measured in IU, a conversion factor ties the unit back to milligrams, and that factor is specific to each substance. Because the factor differs by compound, IU and mg are not interchangeable without knowing the substance in question.

Concentration and Syringe Terms

Concentration. The amount of substance present per unit of volume of solution, usually written as mass per volume, such as mg per mL or mcg per mL. Concentration is set at the moment of reconstitution by the pairing of a fixed peptide amount with a chosen diluent volume. A larger diluent volume produces a lower concentration for the same amount of peptide. The relationship is amount divided by volume, and the reconstitution and blend calculators handle this arithmetic.

U-100. A labeling standard for insulin syringes. U-100 means the syringe scale is calibrated so that 100 units correspond to 1 mL of liquid. On that scale, 1 unit equals 0.01 mL, and 50 units equals 0.5 mL. The unit markings on a U-100 syringe measure volume, meaning how far the liquid sits along the barrel, not the mass of any dissolved substance. Reading that volume from the scale is a measurement task and is independent of what the solution contains.

Tools and supplies

For laboratory and research reference only. Educational content, not medical, dosing, injection, or therapeutic guidance, and not intended for human or animal use. Confirm anything involving health with a licensed professional.