Glossary
A comprehensive glossary of 20+ key terms used in peptide research, with clear definitions, cross-references, and structured JSON-LD semantic markup for integration with search engines and knowledge graphs.
📖 Glossary Terms¶
A¶
Amino Acid¶
Organic compounds that serve as the building blocks of peptides and proteins. Each amino acid contains an amino group (-NH₂), a carboxyl group (-COOH), and a unique side chain (R-group). Standard peptides are composed of L-amino acids linked by peptide bonds. The 20 proteinogenic amino acids form the basis of most natural and synthetic peptides.
See also: Peptide Bond, SPPS
Amidation¶
A post-translational or synthetic modification in which the C-terminal carboxyl group (-COOH) is converted to a carboxamide group (-CONH₂). C-terminal amidation is common in bioactive peptides and generally increases metabolic stability and receptor binding affinity. Examples include Cerebrolysin peptide fragments and Argireline.
See also: Proteolysis
B¶
Bacteriostatic Water¶
Sterile water containing 0.9% benzyl alcohol as a preservative. Used as a solvent for reconstituting lyophilized peptides. The benzyl alcohol inhibits bacterial growth during multi-dose use. Bacteriostatic water is preferred over sterile water for multi-dose peptide vials because it allows repeated access over 7–28 days.
See also: Reconstitution
Bioavailability¶
The fraction of an administered dose that reaches systemic circulation intact. For peptides, bioavailability is influenced by route of administration, molecular weight, lipophilicity, and resistance to proteolytic degradation. Intranasal administration often achieves higher CNS bioavailability than oral or intravenous routes.
See also: Half-life (t½), SC
C¶
CAS Number¶
A unique numeric identifier assigned by the Chemical Abstracts Service to every chemical substance described in the open scientific literature. CAS numbers for peptides enable precise identification across databases, regulatory documents, and analytical references. Format: XXX-XX-X (e.g., 80714-61-0 for Semax).
D¶
Deamidation¶
A non-enzymatic chemical reaction in which the side-chain amide group of asparagine (Asn) or glutamine (Gln) is hydrolyzed to form a free carboxylic acid, converting Asn to Asp and Gln to Glu. Deamidation is a common degradation pathway in peptides and can affect biological activity.
See also: Lyophilization
Disulfide Bridge¶
A covalent bond formed between the thiol (-SH) groups of two cysteine residues, creating a cystine linkage (-S-S-). Disulfide bridges stabilize peptide tertiary structure and are critical for maintaining the bioactive conformation.
E¶
ESI-MS (Electrospray Ionization Mass Spectrometry)¶
An analytical technique that ionizes peptides from solution into the gas phase by applying a high voltage to a capillary tip. ESI produces multiply charged ions, allowing accurate mass determination. For most research peptides (300–5000 Da), ESI-MS provides molecular weight confirmation with accuracy of ±0.01% or better.
See also: Molecular Weight (MW), HPLC
H¶
Half-life (t½)¶
The time required for the concentration of a peptide in plasma or serum to decrease by 50%. Half-life is influenced by proteolytic degradation, renal clearance, and receptor-mediated elimination. Modifications such as amidation, PEGylation, or fatty acid acylation can extend half-life.
See also: Proteolysis, Bioavailability
HPLC (High-Performance Liquid Chromatography)¶
A chromatographic technique used to separate, identify, and quantify peptide compounds. Reversed-phase HPLC (RP-HPLC) with C18 columns and UV detection at 214 nm is standard. Purity ≥ 98% is the typical threshold for research-grade peptides.
See also: ESI-MS
L¶
Lipophilicity (logP)¶
A measure of a compound's affinity for lipid environments relative to aqueous environments (octanol/water partition coefficient). Negative logP = hydrophilic; positive logP = lipophilic. Lipophilicity affects membrane permeability, bioavailability, and tissue distribution.
See also: Bioavailability
Lyophilization (Freeze-Drying)¶
A dehydration process in which a frozen peptide solution is placed under vacuum for ice sublimation. Produces a stable dry powder for extended storage. Must be carefully controlled to avoid degradation.
See also: Reconstitution
M¶
Molecular Weight (MW)¶
The sum of atomic weights of all atoms in a peptide molecule (Da or g/mol). Both monoisotopic and average mass are reported. MW is the primary parameter for LC-MS method development.
See also: ESI-MS
P¶
Peptide Bond¶
A covalent amide bond formed between the carboxyl group of one amino acid and the amino group of another. Peptide bonds have partial double-bond character and define the primary structure.
See also: Amino Acid
pI (Isoelectric Point)¶
The pH at which a peptide carries no net electrical charge. Determined by the sum of ionizable groups (N-terminus, C-terminus, and side chains of Asp, Glu, Arg, Lys, His).
Proteolysis¶
The enzymatic cleavage of peptide bonds by proteases and peptidases. The primary metabolic pathway for peptide degradation. Resistance is achieved through D-amino acid substitution, amidation, cyclization, or N-methylation.
See also: Half-life (t½)
R¶
Reconstitution¶
The process of dissolving lyophilized peptide powder in a suitable solvent. Proper technique — gentle swirling, correct solvent volume, aseptic method — is critical for peptide integrity.
See also: Lyophilization, Bacteriostatic Water
S¶
SC (Subcutaneous)¶
Injection into the subcutaneous tissue layer. The most common route for research peptides with 60–90% bioavailability and ease of administration.
See also: Bioavailability
Solid-Phase Peptide Synthesis (SPPS)¶
The standard method for chemical peptide synthesis on an insoluble resin support. Fmoc chemistry with HBTU/HOBt coupling is most common. Enables synthesis of peptides up to 30–50 amino acids.
T¶
Telomerase¶
A ribonucleoprotein enzyme that adds TTAGGG repeats to chromosome ends, counteracting telomere shortening during cell division. Epitalon uniquely upregulates hTERT expression and activates telomerase in somatic cells.
TFA (Trifluoroacetic Acid)¶
A strong organic acid used in HPLC (ion-pairing agent) and SPPS (cleavage/deprotection). Residual TFA in peptide products (1–10% by weight) should be accounted for in dosing.
TrkB Receptor¶
High-affinity receptor for BDNF; activates MAPK/ERK, PI3K/Akt, and PLCγ pathways. Semax and Noopept exert neurotrophic effects through TrkB-mediated signaling.