The compounds referenced on this page are research-grade reference peptides supplied strictly for in-vitro and other controlled laboratory research. They are not for human or animal consumption, are not FDA approved, and are not drugs, supplements, cosmetics, or treatments for any condition. This article is third-person science education about how peptide names are constructed and read. It does not describe or endorse taking, dosing, or administering any substance, and any question about human health belongs with a licensed clinician.
Why Peptide Names Are So Inconsistent
A single research peptide can appear under four or five different names depending on who is writing about it. A patent may use a development code, a regulatory filing may use an International Nonproprietary Name, a journal article may spell out the amino acid sequence, and a catalog may use an informal shorthand that grew up in the research community. None of these is wrong. Each naming system was built for a different purpose, and the same molecule simply passes through several of them over its history.
For a laboratory, this inconsistency is more than a curiosity. Two materials with similar names can be different molecules, and two materials with very different names can be the same molecule. Reproducible research depends on knowing exactly which sequence, which terminal modifications, and which salt form is in the vial. Names are a convenient label, but the sequence and the analytical data are the real identity of the compound.
This guide walks through the main naming systems in the order a researcher is likely to meet them: sequence notation, development codes, nonproprietary names and their stems, fragment and analog names, and the salt and counterion suffixes that appear on certificates of analysis. The underlying chemistry of what makes a short amino acid chain a peptide is covered in the primer on what peptides are.
Sequence Notation: The Most Precise Name
The most exact way to name a peptide is to write out its amino acid sequence. By convention, sequences are written from the N-terminus, the end carrying a free amino group, to the C-terminus, the end carrying a free carboxyl group. Reading direction matters. The tripeptide Glu-Asp-Arg and the tripeptide Arg-Asp-Glu contain the same three amino acids but are different molecules with different properties.
Two alphabets are in common use. The three-letter code writes each residue as an abbreviation such as Gly, Ala, Glu, or Lys, separated by hyphens. The one-letter code compresses each residue to a single capital letter, so glycine becomes G, glutamic acid becomes E, aspartic acid becomes D, and lysine becomes K. Short sequences are often written both ways, and longer sequences are almost always given in one-letter form because the three-letter version becomes unwieldy.
- Three-letter code: Ala-Glu-Asp-Gly, readable and unambiguous for short chains.
- One-letter code: AEDG, the same tetrapeptide in compact form.
- N-terminal modifications are written at the left, for example Ac- for an acetyl group.
- C-terminal modifications are written at the right, for example -NH2 for an amide.
- D-amino acids are marked with a D- prefix, such as D-Trp, because the default assumption is the natural L form.
- Non-standard residues get their own abbreviations, and a well-written specification defines each one.
Terminal modifications are easy to overlook and they matter. An amidated C-terminus removes a negative charge and is studied for its effect on stability against carboxypeptidases, while an acetylated N-terminus removes a positive charge and is studied for resistance to aminopeptidases. A sequence written without its terminal groups is incomplete, and two materials that differ only in a terminal amide are different compounds for analytical and research purposes.
Development Codes: BPC-157, TB-500, CJC-1295, and PT-141
Many of the best-known research peptides are known by development codes: a short string of letters followed by a number. These codes were typically assigned inside a research program or company to track candidate molecules before any formal name existed, and some of them stuck because the compound was discussed widely under that label long before, or instead of, receiving a nonproprietary name.
The important lesson is that the number in a development code usually does not describe the molecule. It is a catalog or series designation, not a residue count or a molecular weight. The examples below show how often the number and the chemistry are unrelated.
BPC-157
BPC stands for body protection compound, a name drawn from the protein fraction the sequence was originally associated with. The compound itself is a 15-residue peptide, a pentadecapeptide, so the 157 is a designation rather than a size. Its research profile is summarized at BPC-157.
TB-500
TB-500 refers to a synthetic peptide associated with a region of thymosin beta-4, a much larger naturally occurring protein. The code signals the relationship to thymosin beta-4 but does not by itself specify the exact sequence, which is why the certificate of analysis and the stated sequence matter more than the label. See TB-500.
GHRP-2 and GHRP-6
GHRP stands for growth hormone releasing peptide. GHRP-6 happens to contain six residues, which leads many readers to assume the number is a length. GHRP-2 is also a six-residue peptide, however, so the number is a series designation. The family is compared in detail in the GHRP family guide.
CJC-1295 and PT-141
Codes like CJC-1295 and PT-141 follow the common pattern of an originator prefix plus a compound number. PT-141 later received the nonproprietary name bremelanotide, which illustrates how a single molecule can carry both a development code and a formal name at the same time. Profiles are at CJC-1295 and PT-141.
Nonproprietary Names and What Their Stems Mean
When a compound advances far enough in pharmaceutical development, it may receive an International Nonproprietary Name, a single global generic name coordinated through the World Health Organization. These names are built from shared stems, usually endings, that signal a pharmacological family. Learning a handful of stems makes it possible to guess the general research category of an unfamiliar peptide from its name alone.
Stems describe family resemblance, not identical behavior. Two compounds that share a stem can differ substantially in structure, receptor selectivity, and half-life in research models. The stem is a starting point for orientation, and the compound page and published literature are where the specifics live.
- -relin: peptides studied as stimulators of pituitary hormone release, as in sermorelin, tesamorelin, and gonadorelin. See tesamorelin and gonadorelin.
- -glutide: analogs of glucagon-like peptide 1, as in semaglutide. See semaglutide and the GLP-1 incretin research guide.
- -tide: a broad ending used for many peptides, including multi-receptor agonists such as tirzepatide and retatrutide.
- -melanotide: melanocortin-related peptides, as in bremelanotide.
- -pressin and -tocin: analogs related to vasopressin and oxytocin respectively.
Some well-known peptides have a formal name that is rarely used in catalogs. Thymosin alpha-1, for example, has the nonproprietary name thymalfasin, yet research literature and suppliers usually use the descriptive name. When searching the literature for a compound, it is worth searching under every known name, because different research groups and different decades favor different labels.
Descriptive Names, Transliterations, and Community Shorthand
A third group of names grew up informally. Some are descriptive, naming the parent hormone and the change made to it. Others are transliterations from another alphabet, which is why Epithalon and Epitalon both appear in print for the same tetrapeptide. Still others are community abbreviations, such as MT-2 for Melanotan II, that save space but carry no formal standing.
Transliteration variants are harmless as long as the sequence is stated. Epithalon is generally described as the tetrapeptide Ala-Glu-Asp-Gly, or AEDG, and that sequence is what identifies it regardless of spelling. See Epithalon for its research profile. Abbreviations are more hazardous, because the same short string can be reused by different communities for different compounds. A catalog that lists an abbreviation without a sequence, molecular formula, or molecular weight is giving less information than a researcher needs.
Fragments, Analogs, and Modified Forms
Many research peptides are defined relative to a larger parent protein, and their names encode that relationship. Reading these names correctly requires knowing a few conventions.
Residue ranges
A name such as fragment 176-191 identifies a segment by the residue numbers it occupies in the parent protein, counted from the N-terminus. The numbers describe position, not the number of residues in some other sense. Compounds discussed in relation to a growth hormone fragment, such as AOD-9604, are often described this way, and the exact sequence supplied should always be confirmed on the certificate of analysis because modified fragments can add or change residues.
Substitution notation
Substitutions are often written as the original residue, its position, and the replacement. IGF-1 LR3 is a useful example: the name signals a longer form of IGF-1 with an N-terminal extension, the L, and an arginine placed at position 3, the R3. Each part of the name corresponds to a specific structural change. See IGF-1 LR3.
Terminal modifications in the name
Some names spell out terminal changes directly. N-Acetyl Semax Amidate describes the Semax sequence with an acetyl group added at the N-terminus and an amide at the C-terminus. The name is long because it is precise, and it tells a researcher that the compound is not interchangeable with unmodified Semax. See N-Acetyl Semax Amidate and Semax.
Conjugates and extended forms
Names that include terms such as DAC, a lipid description, or PEG indicate that something beyond the amino acid chain has been attached, usually to change how long the molecule persists in a research model. These additions change the molecular weight substantially and must be reflected in the analytical data. How structural changes like these are studied for their effect on exposure is covered in the guide to peptide bioavailability in research models.
Salt Forms and Counterions on the Label
Research peptides are usually isolated as salts. Charged side chains and termini pair with counterions left over from synthesis and purification, most commonly acetate or trifluoroacetate. A label or certificate that reads, for example, a compound name followed by acetate is specifying the salt form, and that detail is part of the material's identity.
The salt form matters for two practical reasons. First, the counterion contributes mass, so the total powder in a vial is not all peptide. The fraction that is peptide is called net peptide content, and it is distinct from chromatographic purity. Second, different counterions can affect solubility and handling in the laboratory. Neither of these facts changes the sequence, but both affect how a research team interprets quantities. The analytical side of this is explained in how peptide purity is measured and in the purity testing and COA questions.
Trade Names and Why Research Suppliers Avoid Them
Approved pharmaceutical products carry brand names, and those brand names refer to a specific finished product: a defined formulation, manufactured under drug regulations, with an approved label. A research-grade reference material is not that product, even when it shares a nonproprietary name or a sequence with the active ingredient of an approved drug.
For this reason, a responsible research supplier names materials by sequence, development code, or nonproprietary name and does not use pharmaceutical brand names to describe them. Using a brand name would suggest an equivalence in formulation, manufacturing controls, and intended use that does not exist. Research materials are supplied for laboratory work only and are not substitutes for any medication. The regulatory framing is covered in the legality and compliance questions.
A Practical Checklist for Reading a Peptide Name
When a laboratory evaluates a catalog listing or a certificate of analysis, the name is only the first line. The checklist below captures the details that together establish what a material actually is.
- Is the full amino acid sequence stated, in one-letter or three-letter code?
- Are N-terminal and C-terminal modifications specified, such as acetylation or amidation?
- Are any D-amino acids or non-standard residues identified and defined?
- Does the stated molecular formula match the sequence and modifications?
- Does the observed mass on the mass spectrometry result match the expected molecular weight?
- Is the salt form or counterion stated, and is net peptide content reported separately from purity?
- Are all known synonyms, including development codes and nonproprietary names, consistent with one another?
Lot-specific documentation is available through the certificate of analysis library. Laboratories setting up an account or requesting materials can do so through the order page, and the wider library of answer-first topics is at /questions.
Why Nomenclature Matters for Reproducible Research
Published research is only reproducible if another laboratory can obtain the same material. When a methods section names a compound only by an informal abbreviation, a later group may source a different salt form, a differently modified terminus, or even a different fragment, and then report results that appear to contradict the original work. A surprising amount of apparent disagreement in the peptide literature traces back to materials that shared a name but not a structure.
The discipline that prevents this is simple to state. Record the full sequence, the terminal modifications, the salt form, the supplier lot, and the analytical results alongside every experiment. Treat the name as an index entry and the sequence plus analytical data as the definition. Laboratories that follow this practice can compare their work with confidence, and readers can interpret published results without guessing which molecule was used.
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Frequently asked questions
What is the most precise way to name a peptide?
The most precise name is the full amino acid sequence written from the N-terminus to the C-terminus, together with any terminal modifications, non-standard residues, and the salt form. Development codes, nonproprietary names, and catalog names are convenient labels, but only the sequence and its modifications define the molecule unambiguously. Analytical data such as mass spectrometry then confirm that the material in a given lot matches that definition. All materials discussed are for laboratory research use only.
Does the number in a code like BPC-157 or GHRP-6 describe the molecule?
Usually not. Numbers in development codes are catalog or series designations assigned during early research. BPC-157 is a 15-residue peptide, so its number is not a length, and although GHRP-6 contains six residues, GHRP-2 is also a six-residue peptide. Treat the number as an identifier and confirm the actual structure from the stated sequence and the certificate of analysis rather than inferring it from the code.
What does the ending -relin or -glutide tell a researcher?
These endings are stems from the International Nonproprietary Name system. The -relin stem marks peptides studied as stimulators of pituitary hormone release, such as tesamorelin and gonadorelin, while -glutide marks analogs of glucagon-like peptide 1, such as semaglutide. Stems indicate a pharmacological family, not identical behavior, so compounds sharing a stem can still differ in structure, selectivity, and persistence in research models.
Why do Epithalon and Epitalon both appear in the literature?
They are transliteration variants of the same name, arising from translation between alphabets. The compound is generally described as the tetrapeptide Ala-Glu-Asp-Gly, or AEDG, and that sequence is what identifies it regardless of spelling. When searching published research, it is worth searching under every spelling and synonym, because different groups and different decades favor different forms of the name.
What do acetate or TFA mean after a peptide name?
They identify the counterion in the salt form of the peptide. Acetate and trifluoroacetate are the most common counterions left from synthesis and purification. The counterion contributes to the total mass of powder in a vial, which is why net peptide content is reported separately from chromatographic purity. The salt form is part of a material's identity and should be recorded alongside the lot number in research records.
Is a research peptide the same as a branded drug with the same active ingredient?
No. A branded drug is a specific finished product with a defined formulation, manufacturing controls, and an approved label. A research-grade reference material that shares a sequence or nonproprietary name is not that product and is not a substitute for any medication. Research materials are supplied for in-vitro and laboratory use only, are not for human or animal consumption, and anyone with a health question should consult a licensed clinician.
How can a lab confirm that a material matches its name?
The standard approach compares the stated sequence and molecular formula against analytical results for the specific lot. Chromatography, typically HPLC, reports purity, and mass spectrometry reports observed mass, which should match the expected molecular weight including terminal modifications and any conjugates. Short sequence permutations can share a mass, so fragmentation-based methods add confidence where sequence order matters. Lot documentation is available through the certificate of analysis library at /coa.
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External references: U.S. Food and Drug Administration · Peptide (Wikipedia)