Peptide glossary29

Semaglutide is a 31-amino-acid peptide that acts as a selective agonist of the GLP-1 (glucagon-like peptide-1) receptor. Its sequence is derived from native human GLP-1 with two modifications — an Aib substitution at position 8 to resist DPP-4 cleavage and a C18 fatty diacid attached to lysine-26 for albumin binding — that together extend its half-life from minutes to about a week. In research, it is studied for its effects on insulin secretion, gastric emptying, and central satiety pathways. It is discussed on Phase 1 Peptides only as an academic comparator in incretin-receptor research literature.

Tirzepatide is a 39-amino-acid peptide engineered as a dual agonist of the GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors. Built on a modified GIP backbone with a C20 fatty diacid for albumin binding, it differs from semaglutide in that it engages two receptor pathways simultaneously rather than one. In published research, this dual engagement produces stronger effects on glycemic and body-composition endpoints than selective GLP-1 agonism at comparable doses. Half-life is about 5 days, supporting once-weekly research protocols.

Retatrutide is a triple agonist that activates GLP-1, GIP, and the glucagon receptor (GCGR). The addition of glucagon receptor activity is what distinguishes it from tirzepatide's dual-agonist design. Glucagon receptor agonism increases hepatic lipolysis and energy expenditure — effects researchers hypothesize complement the satiety and insulin-modulating effects of GLP-1/GIP. The compound is earlier in its published pipeline than semaglutide or tirzepatide, making it a particularly active research subject for mechanism-isolation studies.

5-Amino-1MQ (5-amino-1-methylquinolinium) is a cell-permeable small-molecule inhibitor of NNMT (nicotinamide N-methyltransferase), an enzyme expressed primarily in adipose tissue and liver that methylates nicotinamide using S-adenosyl methionine (SAM) as the methyl donor. NNMT activity connects methionine one-carbon metabolism, NAD+ precursor recycling, and cellular methylation capacity. By inhibiting NNMT, 5-amino-1MQ raises intracellular SAM availability and shifts nicotinamide flux toward NAD+ biosynthesis via the salvage pathway. In rodent research, NNMT inhibition has been associated with alterations in fat mass, energy expenditure, and adipocyte differentiation. As a research tool, it occupies a distinct mechanistic niche from direct NAD+ supplementation: rather than supplying a precursor, it modulates the competing enzymatic pathway that consumes that precursor. While not technically a peptide, 5-amino-1MQ is studied alongside research peptides in NAD+ and metabolic biology contexts.

Mazdutide (IBI362) is a once-weekly synthetic peptide agonist designed to co-activate the glucagon-like peptide-1 receptor (GLP-1R) and the glucagon receptor (GCGR). Its dual-agonist design pairs GLP-1 receptor activity — which drives insulin secretion, gastric emptying delay, and central satiety signaling — with glucagon receptor activity, which promotes hepatic glucose output, fatty acid oxidation, and thermogenesis. This GLP-1/GCGR pairing is mechanistically distinct from tirzepatide's GLP-1/GIP combination: rather than engaging the incretin system via two different pathways, mazdutide targets the GLP-1 and glucagon axes. The same GLP-1/GCGR design is shared by retatrutide's dual component, though retatrutide extends further to triple agonism by adding GIP. Mazdutide has been investigated in published clinical research for metabolic endpoints, and is studied in research contexts as a comparator within the GLP-1/glucagon agonist class.

Cagrilintide is a long-acting synthetic analog of amylin — a 37-amino-acid peptide hormone co-secreted with insulin by pancreatic beta cells. Native amylin has a very short plasma half-life; cagrilintide achieves an approximately one-week half-life suitable for once-weekly research protocols through structural modifications including C-terminal amidation, alanine substitution at position 25, and a C20 fatty acid chain conjugated via a linker for albumin binding. Amylin and its analogs act through amylin receptors (calcitonin receptor complexed with RAMP proteins) expressed in the brainstem and hypothalamus to slow gastric emptying and modulate central satiety pathways — a mechanism complementary to GLP-1 receptor agonism. Research has examined cagrilintide both as a standalone amylin-axis compound and in co-administration with GLP-1 receptor agonists studied in multi-phase research programs, making it a relevant research tool for studying GLP-1/amylin axis synergy in metabolic models.

CJC-1295 is a synthetic analog of growth-hormone-releasing hormone (GHRH) modified for stability. Two versions exist: with DAC (Drug Affinity Complex) for an extended half-life of several days, and No DAC for short-pulse profiles closer to native GHRH. Both variants stimulate the pituitary to secrete growth hormone in episodic bursts. CJC-1295 is most often studied paired with a GHRP (growth-hormone releasing peptide) like Ipamorelin to engage the dual GHRH + ghrelin pathways simultaneously.

Ipamorelin is a pentapeptide ghrelin-receptor agonist (GHRP) that triggers a selective pulse of growth hormone release without the prolactin and cortisol elevation seen with earlier GHRPs like GHRP-6. Its short half-life (~2 hours) makes it especially useful for protocols that aim to mimic native pulsatile GH release. In the research literature it's most often studied in combination with a GHRH analog (CJC-1295) to engage both receptors at once.

Sermorelin is a synthetic 29-amino-acid peptide corresponding to the amino-terminal portion of human growth-hormone-releasing hormone (GHRH) — the shortest native-sequence fragment that retains full biological activity at the pituitary GHRH receptor. Unlike CJC-1295, which uses sequence substitutions to extend half-life, sermorelin preserves the native residue sequence and is rapidly cleared (half-life approximately 10–20 minutes), giving it a pulsatile profile close to endogenous GHRH. In research, it is studied for its direct stimulation of somatotroph cells in the pituitary, its downstream effects on GH secretion, and as a mechanistic comparator to longer-acting GHRH analogs. Because the pituitary response to sermorelin depends on intact somatotroph function, it has also been investigated as a diagnostic research tool for probing the GH axis.

Tesamorelin is a synthetic peptide consisting of the full 44-amino-acid sequence of human GHRH with trans-3-hexenoic acid conjugated to its N-terminus via an amide bond. The fatty acid modification substantially extends plasma half-life compared to native GHRH without altering the core receptor-binding sequence. In the GHRH analog research landscape, it occupies a distinct position from sermorelin (1-29 native sequence) and CJC-1295 (1-29 with stabilizing substitutions): tesamorelin covers the full GHRH sequence and uses a lipid chain rather than amino-acid modification for stability. Published research has examined its effects on visceral adipose tissue dynamics, GH-axis stimulation, and lipid-metabolism endpoints in animal and clinical models.

BPC-157 (Body Protection Compound 157) is a synthetic 15-amino-acid peptide derived from a partial sequence of a protein found in human gastric juice. It's notable for unusual stability in acidic and enzymatic environments, allowing oral administration in animal models — uncommon for peptides. Reported mechanisms in the literature include nitric oxide system modulation and VEGF-mediated angiogenesis. Most published research is in rodent tissue-repair, gut-barrier, and vascular models. It is commonly studied alongside TB-500 in combination protocols.

TB-500 is a synthetic peptide fragment derived from thymosin beta-4 (Tβ4), one of the most abundant proteins in mammalian cells. It interacts with G-actin and is implicated in cellular migration, actin cytoskeleton dynamics, and angiogenesis. In research models, it's studied for tendon, ligament, and cardiac repair endpoints. The combination of TB-500 (cellular migration) with BPC-157 (angiogenesis) is one of the most-replicated peptide stacks in the published literature for tissue-repair research.

GHK-Cu is a copper-bound tripeptide (glycyl-L-histidyl-L-lysine) found naturally in human plasma at concentrations that decline with age. It's been studied for its effects on collagen synthesis, antioxidant activity, and gene expression — notably modulating expression of dozens of genes related to tissue remodeling. Research applications span dermal repair, hair follicle, and longevity models. The copper ion is essential to its activity; GHK without copper has different properties.

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme essential to cellular energy metabolism, redox reactions, and DNA repair. NAD+ levels decline with age, which has driven research interest in NAD+ repletion as a focus of longevity biology studies. While it's not technically a peptide, it's commonly stocked alongside research peptides because it's used in adjacent mitochondrial and longevity research protocols.

MOTS-c is a 16-amino-acid peptide encoded within the mitochondrial DNA — one of the few known mitochondrial-derived peptides. It's been studied for its effects on metabolic homeostasis, insulin sensitivity, and exercise-mimetic pathways in animal models. As a mitochondrial-derived signaling molecule, it sits at the intersection of metabolic and longevity research.

Epitalon is a synthetic tetrapeptide (Ala-Glu-Asp-Gly) derived from epithalamin — a bioregulatory polypeptide fraction isolated from bovine pineal gland extract. It was developed by the Khavinson research group in Russia as part of a systematic program to identify minimum-active short peptide sequences from organ-specific tissue extracts. Research applications center on reported telomerase activation in cell culture and animal models, regulation of pineal melatonin output, and lifespan-extension effects in Drosophila and rodent longevity studies. Its mechanism — how a four-amino-acid peptide activates telomerase — is not fully characterized at the molecular level. The published evidence base is primarily from Russian and Eastern European research institutions.

Glutathione (GSH) is a tripeptide — L-glutamate, L-cysteine, and glycine joined in a gamma-glutamyl linkage — present at millimolar concentrations in most mammalian cells. It is the cell's primary intracellular antioxidant: the free thiol group of the cysteine residue donates an electron to neutralize reactive oxygen species, converting GSH to its oxidized disulfide form (GSSG), which is then reduced back to GSH by glutathione reductase using NADPH. Beyond direct radical scavenging, GSH serves as the obligate co-substrate for the glutathione peroxidase enzyme family, which catalyzes the reduction of hydrogen peroxide and lipid hydroperoxides. Research applications include oxidative stress models, redox biology, cellular detoxification pathway studies, and aging research examining the documented decline of intracellular GSH in aging cell and tissue models.

SS-31 (elamipretide) is a synthetic tetrapeptide (D-Arg-2′,6′-dimethylTyr-Lys-Phe-NH₂) that selectively targets the inner mitochondrial membrane through electrostatic interaction with cardiolipin — a negatively charged phospholipid almost exclusively found at that location. Cardiolipin is essential for the structural organization of electron transport chain complexes and cristae architecture. By associating with cardiolipin, SS-31 is hypothesized to stabilize cristae morphology, reduce electron leak, decrease reactive oxygen species production, and preserve ATP synthesis capacity under cellular stress. It has been investigated in animal and cell models of ischemia-reperfusion injury, heart failure, kidney disease, and aging-associated mitochondrial dysfunction. Its direct inner-membrane targeting distinguishes it mechanistically from other mitochondrial-focused compounds like MOTS-c, which acts via AMPK-dependent nuclear gene regulation.

Selank is a synthetic heptapeptide analog of tuftsin developed in Russia for nootropic and anxiolytic-related research. In animal models it's been studied for effects on GABAergic and serotonergic systems, BDNF expression, and stress-response endpoints. It is structurally short and water-soluble, with a reasonably short half-life that supports nasal administration in published protocols.

Semax is a synthetic heptapeptide analog of an ACTH(4-10) fragment, also of Russian origin. Research focuses on its effects on BDNF and NGF expression, dopaminergic systems, and stroke/ischemia models. Like Selank, it's typically studied via nasal administration and is often paired with Selank in cognitive-research protocols.

DSIP (delta sleep-inducing peptide) is a nonapeptide (Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu) first isolated from cerebral venous blood of rabbits during electrophysiologically defined slow-wave sleep. Despite its historical name, research on DSIP has revealed a broader profile of neuromodulatory effects than the original sleep-inducing label suggests: published animal studies have examined its interactions with the opioid and GABAergic systems, its modulation of ACTH and cortisol secretion, and its reported effects on stress-response endpoints. DSIP is notable for its apparent ability to cross the blood-brain barrier intact — unusual for a peptide of its size — which has made it a subject of interest in studies of central neuropeptide distribution and action. Its short sequence, water solubility, and reported BBB permeability make it a tractable research compound for central nervous system neuropeptide studies.

Kisspeptin refers to a family of peptide fragments encoded by the KISS1 gene that act as endogenous activators of GnRH (gonadotropin-releasing hormone) neurons. It sits upstream of the entire reproductive hormone axis — without functional kisspeptin signaling, the pituitary doesn't release LH and FSH normally. Research applications span reproductive endocrinology, puberty timing, and hypothalamic-pituitary-gonadal axis studies.

High-Performance Liquid Chromatography (HPLC) is the primary analytical technique used to measure peptide purity. A sample dissolved in a solvent is injected into a mobile phase flowing under high pressure through a column packed with stationary-phase particles. Each component in the mixture interacts differently with the stationary phase and elutes at a characteristic retention time. A UV detector — typically set to 220 nm for peptides — records a signal proportional to concentration, producing a chromatogram. Purity is calculated as the peak area of the target compound divided by the total peak area, expressed as a percentage. For research peptides, reverse-phase HPLC (RP-HPLC) is standard: the nonpolar stationary phase separates compounds by hydrophobicity. HPLC is fast, highly reproducible, and sensitive to low-percentage impurities — including truncation fragments, oxidation products, and synthesis byproducts. HPLC purity appears on every Certificate of Analysis (COA) as the headline analytical metric. It is complemented by LC-MS, which confirms molecular identity rather than purity percentage.

Liquid Chromatography–Mass Spectrometry (LC-MS) combines the separation power of liquid chromatography with mass spectrometric detection to confirm compound identity at the molecular level. Where HPLC measures relative peak areas to calculate purity percentages, LC-MS measures the mass-to-charge ratio (m/z) of ionized molecules to verify that the compound in the vial is actually the stated peptide. The technique can identify individual components in a complex mixture at very low concentrations, and can detect synthesis byproducts, truncation fragments, oxidation products, and sequence errors that HPLC alone cannot distinguish from the target compound. On a Certificate of Analysis, LC-MS results typically appear as an observed molecular weight compared against the theoretical mass of the stated peptide. Agreement within instrument accuracy (typically ±0.1–1.0 Da depending on the mass analyzer) constitutes identity confirmation. The combination of HPLC purity percentage and LC-MS identity confirmation on the same COA is the standard dual-assay benchmark for research peptide quality characterization.

A Certificate of Analysis (COA) is a laboratory document that records the analytical results for a specific batch of a research compound. For research peptides, a COA typically includes: the compound name, lot or batch number, the testing laboratory's name, date of analysis, methods used (HPLC for purity, LC-MS for identity), and the numerical results for each assay. HPLC purity is reported as a percentage; mass spectrometry results are reported as observed versus theoretical molecular weight. The COA is lot-specific — it represents a single production batch, not a blanket product-level quality assertion. When evaluating a COA, key checks include: (1) the compound name and batch number match the product in hand; (2) HPLC purity meets the threshold required for the research application; (3) LC-MS observed mass matches the theoretical mass of the stated sequence; and (4) the testing date is recent relative to the batch. Some COAs include additional assays — endotoxin (LAL), residual solvent, heavy metals — though these are not standard for all research peptide batches. Lot-specific COA availability is the standard documentation model for research-use-only compounds.

Lyophilization (freeze-drying) is a dehydration process used to preserve labile compounds — including research peptides — by removing water under vacuum while the sample remains frozen. The process occurs in three stages: freezing the sample; primary drying, in which vacuum is applied to sublime frozen water crystals directly from solid to vapor without passing through liquid phase; and secondary drying to remove residual bound water adsorbed to the compound. For research peptides, lyophilization produces a stable dry powder with substantially extended shelf life compared to solution-phase material. The dry powder form is resistant to the hydrolysis and microbial degradation that degrade peptide solutions over time. Lyophilized peptides are typically stored at −20 °C or 4 °C and are stable for months to years depending on the compound and storage conditions. Before use in a research protocol, the lyophilized powder must be reconstituted with an appropriate solvent — typically bacteriostatic water or sterile water — to produce a working solution. The white-to-off-white powder appearance is the standard supply form for virtually all catalog research peptides.

Research Use Only (RUO) is a designation applied to chemical and biological compounds — including synthetic peptides — that are intended exclusively for laboratory and scientific research purposes. RUO products are not intended for diagnostic, therapeutic, clinical, or consumer use, and are not evaluated or approved by regulatory agencies for any in-human application. The designation establishes that the supplier has no role in clinical or consumer product chains, and that appropriate oversight — institutional review, safety protocols, regulatory compliance — for any research application is the researcher's responsibility. RUO is distinct from terms such as investigational, clinical-grade, or pharmaceutical-grade, which imply regulatory engagement with human-use pathways. For research peptides, RUO means the products are supplied solely for use in laboratory settings: analytical studies, in vitro research, and animal research conducted under appropriate institutional oversight. The designation is not a quality grade — it specifies intended use context, not purity or analytical specifications. Phase 1 Peptides supplies all products strictly as research-use-only materials and makes no representations about human or veterinary applications.

Biological half-life (t₁/₂) is the time required for the concentration of a compound in a biological system to decrease by 50% under physiological conditions. For research peptides, half-life is a critical pharmacokinetic parameter that governs the duration of measurable compound levels and informs research study design — particularly dosing interval, sampling time points, and washout periods in pharmacokinetic experiments. Peptide half-lives vary enormously by structural design. Native peptides are rapidly degraded by ubiquitous serum and tissue proteases, giving half-lives measured in minutes: native GLP-1 is cleared in approximately 2 minutes; native GHRH in approximately 7 minutes. Structural modifications can extend half-life substantially: fatty acid conjugation to albumin-binding sequences (used in semaglutide and cagrilintide), amino acid substitutions to block DPP-4 or protease cleavage sites (used in CJC-1295), and full-sequence analogs retaining the native peptide framework (as in tesamorelin). Understanding the relationship between structural modification and half-life is central to interpreting published pharmacokinetic data and designing valid research protocols. For a cross-class reference spanning GLP-1, GHRH, GHRP, and neuropeptide families, see the Peptide Half-Life Reference guide.

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, which suppresses bacterial growth and extends the usable life of reconstituted peptides from hours (with plain sterile water) to weeks. It is the standard solvent used for peptide reconstitution in research labs. An opened/pierced vial is generally considered usable for 28 days; unopened vials remain stable for years at room temperature.