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A
Acetate salt Chemistry
A common salt form for supplied peptides in which the peptide is paired with acetate counterions. Adds mass beyond the peptide free base; typically lighter than the trifluoroacetate (TFA) salt alternative. See Molecular Weight Database for salt-form implications.
Acetylation Chemistry
The addition of an acetyl group to the N-terminus of a peptide, denoted with the Ac- prefix in a sequence. Blocks enzymatic degradation at the N-terminus and stabilizes the peptide. The true TB-500 fragment is Ac-LKKTETQ.
Aib (alpha-aminoisobutyric acid) Chemistry
A non-standard, non-coded amino acid used in synthetic peptides because it resists cleavage by degradation enzymes. Has no single-letter code and is always written out. Appears in Ipamorelin, Semaglutide, and Tirzepatide.
Albumin binding Pharmacokinetics
A stabilization strategy in which a fatty acid or chemical group is attached to a peptide to make it bind albumin, the most abundant protein in blood plasma. Extends half-life from minutes to days by shielding the peptide from enzymatic clearance and kidney filtration.
Aliquot Storage
A single-use portion of a solution, divided from a larger reconstituted vial before freezing. Aliquoting allows long-term storage of a reconstituted peptide while avoiding damaging freeze-thaw cycles on the whole vial. Standard practice for peptide storage beyond the refrigerated window.
Amidation Chemistry
The conversion of a C-terminal carboxyl group to an amide, denoted with the -NH2 suffix. Improves peptide stability against enzymatic degradation. Many research peptides including Ipamorelin and the GHRPs are C-terminally amidated.
Amino acid Chemistry
The building blocks of peptides and proteins. Twenty standard amino acids exist in biology, each with a three-letter code (Gly) and single-letter code (G). Synthetic peptides may also contain non-standard residues like Aib. See the Sequence Database for the full code table.
Aggregation Degradation
The clumping of peptide molecules in solution into forms that are no longer active. Accelerated by mechanical stress — shaking, foaming, air-liquid interface exposure. The chemical basis for the universal rule to swirl, never shake, a reconstituted vial.
B
Bacteriostatic water (BAC water) Solvent
Sterile water containing 0.9% benzyl alcohol as a bacteriostatic preservative. The standard solvent for reconstituting research peptides intended for multi-dose use. See the BAC Water reference for full comparison.
Benzyl alcohol Solvent
The 0.9% preservative added to bacteriostatic water that inhibits bacterial growth in multi-dose vials. Bacteriostatic rather than bactericidal — prevents growth without actively killing existing bacteria. Mild enough not to damage peptide structure.
Bioavailability Pharmacokinetics
The fraction of an administered dose that reaches systemic circulation in active form. Route of administration is the single biggest determinant — subcutaneous injection typically yields 80–100%, oral for most peptides less than 1%. See Administration Methods.
Blood-brain barrier (BBB) Pharmacology
The selective barrier separating the bloodstream from the central nervous system. Most peptides cross it poorly, which is one reason intranasal delivery matters for nootropic peptides — the olfactory pathway allows some compounds to partially bypass the BBB.
BPC-157 Peptide
A 15-amino-acid peptide (sequence GEPPPGKPADDAGLV) derived from a larger protein in gastric juice. Studied for tissue and gut repair, angiogenesis, and cytoprotection. Molecular weight 1,419.5 g/mol; half-life approximately 4 hours.
C
C-terminus Chemistry
The carboxyl-terminated end of a peptide chain. By convention, sequences are written with the C-terminus on the right. C-terminal amidation (denoted -NH2) is a common stabilizing modification.
Certificate of Analysis (COA) Quality
The document issued by a peptide manufacturer for a specific batch, listing the actual peptide content, salt form, purity, water content, and other batch-specific parameters. The authoritative source for values that vary between batches.
CJC-1295 Peptide
A 29-amino-acid GHRH analog, produced in two forms — without DAC (Modified GRF 1-29, half-life ~30 min) and with DAC (Drug Affinity Complex, half-life ~6–8 days). The two share nearly the same backbone but differ radically in duration due to the DAC modification.
Clearance Pharmacokinetics
The rate at which the body removes a compound from circulation, through metabolism (enzymatic breakdown), excretion (primarily kidneys), or both. Fast clearance produces a short half-life; slow clearance produces a long one.
Concentration Math
The mass of peptide per volume of solvent, typically expressed in mg/mL or mcg/mL. Calculated as labeled peptide mass divided by bacteriostatic water volume. See the Reconstitution Reference for the full formulas.
Cyclic peptide Chemistry
A peptide whose backbone forms a closed ring rather than a linear chain. Cyclization improves resistance to enzymatic degradation and gives the peptide a more rigid, defined structure. PT-141 and Melanotan II are cyclic heptapeptides.
D
DAC (Drug Affinity Complex) Chemistry
A modification appended to CJC-1295 that causes the peptide to bind blood proteins, extending its half-life from roughly 30 minutes (without DAC) to 6–8 days (with DAC). The most striking single-modification half-life extension in common research peptides.
D-amino acid Chemistry
The mirror-image form of an amino acid, denoted with a D- prefix (D-Ala, D-Phe). Naturally occurring amino acids are almost all L-form; incorporating D-residues into a synthetic peptide slows enzymatic degradation because enzymes are shape-specific.
Dalton (Da) Chemistry
The unit of atomic and molecular mass. For peptide purposes, equivalent to grams per mole (g/mol). A peptide of molecular weight 4,113.6 g/mol is 4,113.6 daltons.
DPP-4 (dipeptidyl peptidase-4) Pharmacology
An enzyme that cleaves peptide bonds at specific positions, rapidly degrading native GLP-1 and many other peptides. Synthetic modifications like Aib substitution are specifically designed to resist DPP-4 cleavage, which is why lipidated GLP-1 agonists survive so much longer than the native hormone.
E
Endotoxin (pyrogen) Quality
Bacterial cell wall fragments that persist even after sterilization and cause reactions when injected. Pharmaceutical-grade solvents and peptides are tested to be pyrogen-free. This is a core reason tap water and consumer distilled water are unacceptable reconstitution solvents.
Epitalon Peptide
A four-amino-acid peptide studied for effects on the pineal gland and telomerase activity. The smallest peptide in the standard research library — molecular weight 390.3 g/mol.
F
First-pass metabolism Pharmacokinetics
The metabolic processing of an orally administered compound by the liver before it reaches general circulation. One of the three main reasons peptide oral bioavailability is so poor — even peptides that survive digestion are aggressively cleared on first pass through the liver.
Free base Chemistry
The peptide molecule itself, without associated salt counterions or bound water. Molecular weights published in chemical databases refer to the free-base form; the powder in a vial always weighs more because it includes salt and hydration.
Freeze-thaw cycle Storage
The full sequence of freezing a reconstituted solution and thawing it back to liquid. Each cycle inflicts a small amount of cumulative degradation on the peptide, which is why aliquoting before freezing matters — each aliquot is thawed only once.
G
GHRH analog Peptide class
A peptide that mimics growth hormone-releasing hormone, stimulating pituitary GH release. Includes Sermorelin (unmodified GHRH 1-29), CJC-1295 with and without DAC, and Tesamorelin.
GHRP Peptide class
Growth hormone-releasing peptide — a class of synthetic peptides that stimulate GH release by acting on the ghrelin receptor. Includes GHRP-2, GHRP-6, and Hexarelin. Mechanistically distinct from GHRH analogs though functionally related.
GHK-Cu Peptide
A copper-bound tripeptide (Gly-His-Lys plus copper). Studied for skin remodeling, wound healing, and hair follicle activity. Notable for being pale blue in solution (from the copper) rather than clear — this is normal, not a sign of degradation.
GLP-1 receptor agonist Peptide class
A peptide that binds and activates the GLP-1 receptor. Includes Semaglutide (single agonist), Tirzepatide (dual GIP/GLP-1 agonist), and Retatrutide (triple GIP/GLP-1/glucagon agonist). All are lipidated for albumin binding and multi-day half-lives.
GRCh37 / GRCh38 Genomics
Successive versions of the human reference genome. Also called hg19 and hg38 respectively. All four major consumer DNA testing services use GRCh37; most current research databases use GRCh38. Position numbers differ between builds. See Raw DNA File Format Reference.
H
Half-life Pharmacokinetics
The time required for the plasma concentration of a peptide to fall by half. Ranges from roughly 1–2 minutes for native unmodified peptides like VIP to about 7 days for the lipidated GLP-1 agonist Semaglutide. See Half-Life Reference.
HPLC purity Quality
The purity of a peptide as measured by high-performance liquid chromatography, typically reported as a percentage on the certificate of analysis. Research peptides commonly report 95–99% HPLC purity.
Hydrolysis Degradation
The chemical breakdown of a peptide bond by reaction with water. The core reason reconstituted peptides are less stable than lyophilized ones — the solvent that dissolves the peptide is also the reactant that degrades it.
Hygroscopic Chemistry
Attracting and retaining moisture from the air. Lyophilized peptides are hygroscopic, which is why sealed vials matter and why bound water contributes mass beyond the peptide free base.
I
IGF-1 Peptide
Insulin-like growth factor 1, a 70-amino-acid protein. Engineered variants studied as research peptides include IGF-1 LR3 (long-acting, 83 residues) and IGF-1 DES (67 residues). The largest peptides in the standard database — MW around 7,000–9,000 g/mol.
Insulin syringe (U-100) Equipment
The standard syringe for research peptide subcutaneous administration. Calibrated so that 100 units = 1 mL, meaning 1 unit = 0.01 mL. Available in 0.3 mL (30-unit), 0.5 mL (50-unit), and 1 mL (100-unit) capacities.
Intramuscular (IM) Administration
Administration by injection into muscle tissue, using a longer needle than subcutaneous injection. Yields bioavailability similar to subcutaneous (~80–100%) but with faster onset due to greater vascularity.
Intranasal Administration
Administration by spray into the nasal cavity, where the vascularized nasal mucosa absorbs the peptide. Bioavailability roughly 1–30%; the route developed for nootropic peptides like Semax and Selank, and one that allows partial bypass of the blood-brain barrier.
Ipamorelin Peptide
A five-amino-acid selective growth hormone secretagogue with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. Molecular weight 711.9 g/mol; half-life approximately 2 hours. Notable for its selectivity — stimulates GH release without significantly affecting cortisol or prolactin.
IU (International Unit) Math
A unit of biological activity, not mass — defined differently for each substance based on its measured effect. For research peptides sold by mass in mg or mcg, IU conversions apply only to specific compounds and are not universal.
K
kDa (kilodalton) Chemistry
One thousand daltons, i.e. 1,000 g/mol. Used to express molecular weight for larger peptides and small proteins. Semaglutide at 4,113.6 g/mol is roughly 4.1 kDa; IGF-1 LR3 at 9,111 g/mol is about 9.1 kDa.
L
Lipidation Chemistry
The attachment of a fatty acid chain to a peptide, which promotes albumin binding and dramatically extends half-life. The mechanism behind the multi-day half-lives of Semaglutide and Tirzepatide.
L-amino acid Chemistry
The naturally occurring form of an amino acid. Nearly all amino acids in biology are the L-form; the D-form is the mirror image and is used deliberately in synthetic peptide design for stability.
Lyophilized Storage
Freeze-dried. The state in which research peptides are supplied — as a dry powder in a sealed vial. Lyophilized peptide is far more stable than reconstituted peptide because the water that drives hydrolysis has been removed.
M
mcg (microgram) Math
One millionth of a gram; one thousandth of a milligram. Most peptide research doses are in the mcg range — for example, a common BPC-157 dose is 250 mcg (0.25 mg). Confusing mcg and mg produces a 1,000-fold dosing error.
mg (milligram) Math
One thousandth of a gram; 1,000 mcg. Peptide vials are commonly labeled by mass in mg (e.g. 5 mg, 10 mg vial). The labeled mg refers to the gross weight of the lyophilized powder, not the net peptide free base.
Molar concentration Math
The concentration of a solution expressed in moles per liter (M, mM, µM). For peptides, calculated as mass concentration divided by molecular weight. Rarely needed for routine reconstitution; standard in receptor-binding and cell-culture assays.
Molecular formula Chemistry
The exact atom count of a molecule — for example, BPC-157 is C62H98N16O22. Changes with salt form and modifications, so the formula on a certificate of analysis or PubChem entry is specific to the free base of that peptide.
Molecular weight (MW) Chemistry
The mass of one mole of a compound, in grams per mole (g/mol). For peptides, this is usually reported as the free-base average molecular weight — the mass of the peptide molecule alone, excluding salt counterions and bound water. See Molecular Weight Database.
N
Net peptide content Chemistry
The mass of actual peptide free base in a vial, excluding salt counterions and bound water. Typically lower than the labeled gross weight of the lyophilized powder. Reported on the certificate of analysis and used for precise mass work.
No-call Genomics
A position in a raw DNA file that the genotyping chip could not confidently read. Represented as -- in 23andMe files or 0 in AncestryDNA allele columns. Must be handled explicitly when parsing, not treated as a valid genotype.
Nootropic peptide Peptide class
A peptide studied for effects on cognition, mood, or neuroprotection. Semax and Selank are the defining examples — both seven-residue peptides sharing a -Pro-Gly-Pro stabilizing tail and developed for intranasal delivery.
N-terminus Chemistry
The amino-terminated end of a peptide chain. By convention, sequences are written with the N-terminus on the left. N-terminal acetylation (denoted Ac-) is a common stabilizing modification.
O
Oral administration Administration
Administration by swallowing. For most peptides, bioavailability is under 1% due to stomach acid, digestive enzymes, and first-pass metabolism. Viable only for peptides specifically engineered for oral delivery (e.g. SNAC-formulated oral semaglutide) or for non-peptide small molecules.
Oxidation Degradation
A degradation pathway in which oxygen-sensitive amino acids (particularly methionine and cysteine) react with dissolved oxygen. Reduced by cold storage, minimizing air exposure, and keeping vials sealed.
P
Peptide bond Chemistry
The amide linkage connecting adjacent amino acids in a peptide chain. Formed by condensation (with loss of a water molecule) during peptide synthesis, and cleaved by hydrolysis during degradation.
Pharmacokinetics (PK) Pharmacology
The study of how a compound moves through the body — absorption, distribution, metabolism, and excretion. For peptides, half-life and bioavailability are the two most commonly cited PK parameters.
Plasma half-life vs duration of effect Pharmacokinetics
Two related but distinct concepts. Plasma half-life is how long the peptide molecule remains in blood. Duration of effect is how long the biological response persists. These can diverge substantially — nootropic peptides like Semax have minutes of plasma half-life but effects that outlast plasma presence.
PubChem CID Reference
A unique numeric identifier assigned to a chemical compound in the PubChem database, the reference resource for verifying molecular formula, molecular weight, and structural data for research peptides.
Pyrogen Quality
A fever-inducing contaminant, typically bacterial endotoxin, that persists even after sterilization of a solvent or preparation. See Endotoxin.
R
Raw DNA file Genomics
A plain text file containing the genotype results from a consumer DNA test — typically several hundred thousand SNPs listed with rsID, chromosome, position, and genotype. See the Raw DNA File Format Reference.
Reconstitution Handling
The process of dissolving a lyophilized peptide in a solvent (typically bacteriostatic water) to produce a dosable liquid solution. See the Reconstitution Reference for the full procedure and math.
Residue Chemistry
An amino acid as it exists within a peptide chain — "residue" refers to what remains after the amino acid has joined the chain via peptide bonds. A 15-residue peptide has 15 amino acids linked together.
rsID Genomics
A reference SNP identifier — a standardized name from the dbSNP database that allows the same genetic variant to be referenced consistently across any dataset or study. rsIDs are build-independent, unlike position numbers.
S
Salt form Chemistry
The counterion form in which a synthetic peptide is isolated — most commonly trifluoroacetate (TFA) or acetate. The salt form adds mass beyond the peptide free base and is listed on the certificate of analysis.
Semaglutide Peptide
A 31-amino-acid lipidated GLP-1 receptor agonist. Molecular weight 4,113.6 g/mol; half-life approximately 7 days. The long half-life comes from a fatty acid chain that binds albumin.
Sequence Chemistry
The ordered list of amino acids making up a peptide, written from the N-terminus (left) to C-terminus (right). Everything else about a peptide — molecular weight, structure, function — follows from the sequence. See Sequence Database.
SNAC Chemistry
Sodium N-(8-[2-hydroxybenzoyl] amino) caprylate — the permeation enhancer that makes oral semaglutide viable by temporarily protecting the peptide and helping it cross the stomach lining. Achieves roughly 1% oral bioavailability, requiring approximately 100-fold higher dose than the injectable form.
SNP Genomics
Single nucleotide polymorphism — a single-base variation in the DNA sequence at a specific position. The units of data in a consumer raw DNA file; each row records the SNP identifier (rsID), its location, and the observed genotype.
Sterile water for injection Solvent
Pyrogen-free sterile water containing no preservative. Suitable for single-use reconstitution within 24 hours but not for multi-dose vials because it lacks the bacteriostatic protection of BAC water's benzyl alcohol.
Subcutaneous (subQ) Administration
Administration by injection into the fatty layer between skin and muscle, using a short fine needle. The default route for research peptides — bioavailability typically 80–100% with simple equipment (U-100 insulin syringe).
Sublingual Administration
Administration by absorption through the mucosa under the tongue. Bypasses digestive tract and first-pass liver metabolism, yielding bioavailability of roughly 3–10% — better than oral, worse than injection. Works only for small, short peptides.
T
TB-500 Peptide
An ambiguous label. Technically, TB-500 is a synthetic 7-amino-acid fragment (Ac-LKKTETQ) of Thymosin β4. In practice, most material sold as TB-500 is full-length 43-amino-acid Thymosin β4 itself (MW ~4,921 g/mol). Always confirm which molecule a certificate of analysis describes.
TFA salt Chemistry
Trifluoroacetate salt — the most common counterion form for synthetic peptides, derived from standard HPLC purification. Heavier per counterion than the acetate salt alternative, and one reason the labeled powder weight differs from net peptide content.
Thymosin β4 Peptide
A 43-amino-acid peptide (sequence beginning Ser-Asp-Lys-Pro-Asp-Met-Ala-Glu-Ile-Glu-Lys...) studied for tissue repair and actin regulation. Most material sold as "TB-500" is actually Thymosin β4 rather than the true 7-residue fragment.
Tirzepatide Peptide
A 39-amino-acid dual GIP/GLP-1 receptor agonist with molecular formula C225H348N48O68. Molecular weight 4,813.5 g/mol; half-life approximately 5 days. Lipidated for albumin binding.
Topical Administration
Administration by application to the skin. Systemic bioavailability is typically under 1%, so topical is appropriate only when the target is the local tissue itself — as with GHK-Cu in cosmetic research contexts.
U
U-100 Equipment
The unit scale for standard insulin syringes: 100 units = 1 mL, so 1 unit = 0.01 mL. Research peptide dosing is typically expressed in units on a U-100 syringe for practical injection.
UniProt Reference
A comprehensive protein sequence and function database. The authoritative reference for sequences of peptides derived from natural proteins — for example, Sermorelin as GHRH residues 1-29.
V
VCF (Variant Call Format) Genomics
A standardized file format for storing genetic variants, used by whole genome sequencing services like Nebula Genomics. More complex than the four-column text files used by chip-based tests like 23andMe.
Vial Storage
The sealed glass container in which lyophilized peptide is supplied, closed with a rubber stopper that permits multiple needle entries. The vial doubles as the reconstitution and multi-dose storage container after BAC water is added.
All compounds referenced in this glossary are discussed strictly for in vitro research and laboratory use. None are approved by the FDA for human consumption, therapeutic use, or veterinary application. This glossary is provided for educational and reference purposes only and does not constitute medical advice.