What Are Research Peptides? A Complete Introduction
An introduction to research peptides covering what they are, how they are used in scientific research, common categories, quality indicators, and regulatory considerations.
What Are Peptides?
Peptides are short chains of amino acids held together by peptide bonds. The boundary between peptides and proteins is somewhat arbitrary, but generally anything under 50 amino acids gets called a peptide, and anything larger is a protein. That smaller size matters -- it changes how these molecules fold, how they interact with receptors, and how easily they can be synthesized in a lab.
Your body already produces thousands of peptides. They act as hormones, neurotransmitters, antimicrobial agents, and signaling molecules that coordinate everything from appetite to wound healing. Research peptides are synthetic versions of these natural compounds, manufactured under controlled conditions for use in laboratory experiments.
How They Are Made
The workhorse behind modern peptide production is solid-phase peptide synthesis, or SPPS. Bruce Merrifield developed this technique in 1963 and won the Nobel Prize in Chemistry for it two decades later. The core idea is elegant: you anchor the first amino acid to an insoluble resin bead, then build the chain one residue at a time.
Each cycle follows the same logic. A protected amino acid is coupled to the growing chain. The protecting group is removed. The next amino acid is coupled. Once the full sequence is assembled, the peptide is cleaved from the resin and purified -- typically by HPLC (High-Performance Liquid Chromatography), which separates the target peptide from truncated sequences and side products. The final step is lyophilization: freeze-drying the purified material into a stable powder that can be stored and shipped without degradation.
SPPS can reliably produce peptides up to about 50 residues. Beyond that, yields drop and side reactions accumulate, which is one reason why longer sequences are usually produced through recombinant expression in bacteria or yeast instead.
Common Categories in Peptide Research
Tissue Repair and Healing
BPC-157 is a 15-amino-acid fragment derived from a protein found in gastric juice. It has been studied extensively in rodent models of tendon, ligament, and muscle injury, where it appears to accelerate angiogenesis and modulate growth factor expression. TB-500 (Thymosin Beta-4) is a naturally occurring 43-amino-acid peptide involved in actin regulation, cell migration, and tissue repair. GHK-Cu, a copper-binding tripeptide, shows up repeatedly in wound healing literature -- it promotes collagen synthesis and has been studied for its remodeling effects in skin and connective tissue.
Longevity and Cellular Health
SS-31 (Elamipretide) is a mitochondria-targeted tetrapeptide that concentrates in the inner mitochondrial membrane. Researchers use it to study how mitochondrial dysfunction contributes to age-related disease. FOXO4-DRI gained attention for its ability to selectively induce apoptosis in senescent cells in mouse models -- a targeted approach to clearing the "zombie cells" that accumulate with age. NAD+ precursor peptides support research into cellular energy metabolism and the decline of NAD+ levels during aging.
Cognitive and Neuroprotective
Semax, derived from a fragment of ACTH (adrenocorticotropic hormone), has been studied in models of cerebral ischemia and neurodegeneration. Russian researchers have published extensively on its neurotrophic effects. Selank is a synthetic analogue of the immunopeptide tuftsin, investigated for anxiolytic-like properties in animal behavioral assays. Dihexa is a smaller molecule studied for its interaction with the hepatocyte growth factor / c-Met receptor system, with published data suggesting effects on synaptic connectivity in rodent hippocampal models.
Metabolic Research
Semaglutide, a GLP-1 receptor agonist, hardly needs introduction at this point -- it has become one of the most studied peptides in metabolic research over the past several years. Tirzepatide takes a dual approach, activating both GIP and GLP-1 receptors, and has generated significant clinical interest. AOD-9604 is a modified fragment (residues 177-191) of human growth hormone, studied specifically for its effects on lipid metabolism without the broader growth-promoting activity of the full hormone.
How to Evaluate Peptide Quality
Purity
Peptide purity is determined by HPLC and expressed as a percentage. For most standard research applications, a purity above 95% is adequate. High-sensitivity assays -- binding studies, dose-response curves where impurities could confound results -- typically call for 98% or higher. Pharmaceutical-grade reference standards push past 99%, but that level of purity is rarely necessary for routine lab work and comes at a significant cost premium.
Certificates of Analysis
A proper Certificate of Analysis (COA) should show the actual HPLC chromatogram, not just a number. It should include mass spectrometry data confirming the molecular weight matches the target sequence, a batch or lot number for traceability, and the name of the testing lab along with the analysis date. If a supplier provides a COA that lacks any of these elements, that is a red flag.
Third-Party Verification
The most reliable quality assurance comes from independent testing by accredited laboratories. Janoshik Analytical, for example, has become a widely recognized name in the research peptide space specifically because they operate independently from the manufacturers. A third-party COA removes the conflict of interest that exists when a supplier tests their own product.
Applications in the Lab
Research peptides are tools for laboratory investigation. In cell culture experiments, they help researchers study how specific signaling pathways respond to peptide stimulation. Binding assays measure how tightly a peptide interacts with its target receptor and how selective it is over related receptors. Stability studies expose peptides to different temperatures, pH levels, and enzymatic environments to understand degradation kinetics. Structure-activity relationship (SAR) work -- modifying a peptide's sequence and observing how each change affects function -- is one of the foundational methods in peptide drug discovery.
Animal model research represents another major application, though it requires institutional ethics review and appropriate regulatory approvals before any in-vivo work begins.
Regulatory Status
Research peptides are classified as research chemicals, not drugs or supplements. They are not approved for human consumption, and selling them for that purpose is illegal in most jurisdictions. Buyers are expected to have a legitimate research purpose, and some peptides carry additional restrictions depending on local laws. It is the researcher's responsibility to understand and comply with the regulations that apply in their jurisdiction.
Handling and Storage
Lyophilized peptides are relatively stable, but they degrade quickly once reconstituted if you are not careful. Store the dry powder at -20 degrees Celsius or colder. When you are ready to use a peptide, reconstitute it with bacteriostatic water or an appropriate buffer, and work under aseptic conditions. Keep reconstituted solutions refrigerated, protected from light, and use them within the timeframe recommended for that specific peptide. Document everything -- storage temperatures, reconstitution dates, solvent used -- because poor record-keeping is one of the most common sources of irreproducible results in peptide research.
For more detail on storage protocols, see our Peptide Storage Guide.
Choosing a Supplier
Not all peptide suppliers are equal, and price alone is a poor indicator of quality. The most important question is whether a supplier provides independently verified COAs for every batch. Beyond that, look for transparency about synthesis methods, purity specifications, and shipping conditions. A supplier that maintains cold-chain integrity and can answer technical questions about their products is far more trustworthy than one offering suspiciously low prices with vague documentation.
At PeptidesDirect, every batch ships with a Janoshik-verified Certificate of Analysis. We believe independent testing is not optional -- it is the baseline for credible research supply.
FOR RESEARCH USE ONLY. The information provided in these articles is for educational and research purposes only. Not intended as medical advice. All products are sold strictly for in-vitro research and laboratory use.