The basic definition
A peptide is a chain of amino acids linked together by peptide bonds. Proteins are also chains of amino acids, but peptides are shorter - typically defined as fewer than 50 amino acids, though the boundary is not strict. Insulin, for example, has 51 amino acids and sits right on the line between peptide and small protein.
Amino acids are organic molecules that share a common backbone: an amine group (NH₂), a carboxyl group (COOH), and a variable side chain that gives each amino acid its distinct properties. When the carboxyl group of one amino acid bonds to the amine group of another, a water molecule is released and a peptide bond forms. String enough of these together and you have a peptide.
Why peptides are studied
Peptides occur naturally throughout the human body. Hormones like glucagon and oxytocin are peptides. So are many signalling molecules, antimicrobial compounds, and fragments released when larger proteins are broken down. Because peptides interact with specific receptors on cell surfaces, they can influence a wide range of biological processes - which is why they attract research interest across metabolism, immunology, neuroscience, and more.
The interest in synthetic peptides follows from this: if a naturally occurring peptide has a measurable effect in a biological system, a synthetic version of that peptide (or a modified analogue) can be used in laboratory settings to study, replicate, or isolate that effect.
Lyophilization and vial format
Most research peptides are sold in lyophilized form - freeze-dried into a white or off-white powder. Lyophilization removes water from the peptide solution, dramatically extending shelf life and stability during storage and shipping. Before use in research, the powder must be reconstituted by adding a sterile liquid (typically bacteriostatic water) to dissolve it back into solution.
The concentration of the resulting solution depends on how much liquid is added to the vial. This arithmetic is at the core of peptide research preparation.
Purity and synthesis
Synthetic peptides are produced by solid-phase peptide synthesis (SPPS), a method developed by Robert Bruce Merrifield, who received the 1984 Nobel Prize in Chemistry for the work. SPPS builds the peptide chain one amino acid at a time while anchored to a solid resin support, then cleaves and purifies the final product.
Purity is typically reported as a percentage measured by high-performance liquid chromatography (HPLC). Research-grade peptides generally carry purity figures above 98%, meaning less than 2% of the mass consists of truncated sequences, deletion products, or other synthesis impurities.
The research use context
Peptides sold for research are not pharmaceutical products. They are not manufactured under the same regulatory framework as medicines, are not approved for administration to humans or animals, and are not accompanied by clinical safety data specific to the supplied lot. The "research use only" designation reflects this - they are tools for scientific study, not clinical preparations.
References: Merrifield RB. Solid phase peptide synthesis. J Am Chem Soc. 1963. Kastin AJ (ed). Handbook of Biologically Active Peptides. Academic Press, 2013.
The basic definition
A peptide is a chain of amino acids linked together by peptide bonds. Proteins are also chains of amino acids, but peptides are shorter - typically defined as fewer than 50 amino acids, though the boundary is not strict. Insulin, for example, has 51 amino acids and sits right on the line between peptide and small protein.
Amino acids are organic molecules that share a common backbone: an amine group (NH₂), a carboxyl group (COOH), and a variable side chain that gives each amino acid its distinct properties. When the carboxyl group of one amino acid bonds to the amine group of another, a water molecule is released and a peptide bond forms. String enough of these together and you have a peptide.
Why peptides are studied
Peptides occur naturally throughout the human body. Hormones like glucagon and oxytocin are peptides. So are many signalling molecules, antimicrobial compounds, and fragments released when larger proteins are broken down. Because peptides interact with specific receptors on cell surfaces, they can influence a wide range of biological processes - which is why they attract research interest across metabolism, immunology, neuroscience, and more.
The interest in synthetic peptides follows from this: if a naturally occurring peptide has a measurable effect in a biological system, a synthetic version of that peptide (or a modified analogue) can be used in laboratory settings to study, replicate, or isolate that effect.
Lyophilization and vial format
Most research peptides are sold in lyophilized form - freeze-dried into a white or off-white powder. Lyophilization removes water from the peptide solution, dramatically extending shelf life and stability during storage and shipping. Before use in research, the powder must be reconstituted by adding a sterile liquid (typically bacteriostatic water) to dissolve it back into solution.
The concentration of the resulting solution depends on how much liquid is added to the vial. This arithmetic is at the core of peptide research preparation.
Purity and synthesis
Synthetic peptides are produced by solid-phase peptide synthesis (SPPS), a method developed by Robert Bruce Merrifield, who received the 1984 Nobel Prize in Chemistry for the work. SPPS builds the peptide chain one amino acid at a time while anchored to a solid resin support, then cleaves and purifies the final product.
Purity is typically reported as a percentage measured by high-performance liquid chromatography (HPLC). Research-grade peptides generally carry purity figures above 98%, meaning less than 2% of the mass consists of truncated sequences, deletion products, or other synthesis impurities.
The research use context
Peptides sold for research are not pharmaceutical products. They are not manufactured under the same regulatory framework as medicines, are not approved for administration to humans or animals, and are not accompanied by clinical safety data specific to the supplied lot. The "research use only" designation reflects this - they are tools for scientific study, not clinical preparations.
References: Merrifield RB. Solid phase peptide synthesis. J Am Chem Soc. 1963. Kastin AJ (ed). Handbook of Biologically Active Peptides. Academic Press, 2013.
