Introduction
Peptide research uses specialized terminology spanning biochemistry, pharmacology, analytical chemistry, and regulatory science. This glossary defines 50 essential terms that researchers working with research peptides encounter regularly, providing a quick reference for both new and experienced researchers.
Core Biochemistry Terms
Amino acid: The building block of peptides and proteins; organic compounds containing an amino group, a carboxyl group, and a unique side chain. Peptide bond: The amide bond (-CO-NH-) formed between the carboxyl group of one amino acid and the amino group of another, releasing water. N-terminus: The free amino (-NH2) end of a peptide chain, the starting point for sequence notation. C-terminus: The free carboxyl (-COOH) end of a peptide chain. Molecular weight (MW): The sum of atomic masses of all atoms in a molecule, expressed in Daltons (Da). Hydrophobicity: The tendency of a molecule to repel water; amino acids with nonpolar side chains are hydrophobic. Amphipathic: Having both hydrophobic and hydrophilic regions in the same molecule, enabling membrane interaction.
Synthesis Terms
SPPS (Solid-Phase Peptide Synthesis): The dominant method for chemical synthesis of research peptides, using a solid resin support. Fmoc: 9-fluorenylmethoxycarbonyl; a base-labile N-terminal protecting group used in modern SPPS. Coupling reagent: A chemical that activates the carboxyl group of an incoming amino acid for efficient peptide bond formation. Lyophilization: Freeze-drying; the process of removing water from a solution under vacuum to produce a stable dry powder. Crude peptide: The raw product of SPPS before purification, containing target peptide and synthesis impurities. Preparative HPLC: Large-scale HPLC used for purifying peptides from crude synthesis mixtures.
Analytical Terms
HPLC (High-Performance Liquid Chromatography): The primary method for measuring peptide purity based on peak area in a chromatogram. Mass spectrometry (MS): Analytical technique confirming peptide identity by measuring molecular weight. Purity (area %): The fraction of total UV-absorbing material in an HPLC sample that is the target peptide. CoA (Certificate of Analysis): The quality document accompanying a research peptide containing analytical data. Karl Fischer titration: The method for measuring water content in lyophilized peptides. TFA (Trifluoroacetic acid): Reagent used in SPPS that forms salts with peptide basic groups, contributing non-active mass.
Pharmacology Terms
Half-life (t½): The time for plasma concentration to decrease by 50% after administration. Bioavailability: The fraction of an administered dose reaching systemic circulation. Receptor agonist: A compound that binds and activates a receptor, producing a biological response. Receptor antagonist: A compound that binds without activating, blocking agonist access. EC50: The concentration producing 50% of maximum response; a potency measure. Kd: Dissociation constant; the concentration at which 50% of receptors are occupied at equilibrium; a binding affinity measure. Pharmacokinetics (PK): The study of how a compound is absorbed, distributed, metabolized, and eliminated. Desensitization: Reduced receptor responsiveness with continued agonist stimulation. Downregulation: Reduction in total receptor number through degradation exceeding synthesis.
Research Peptide-Specific Terms
GHRP (Growth Hormone-Releasing Peptide): A class of synthetic GHS-R1a agonists that stimulate GH release. GHRH (Growth Hormone-Releasing Hormone): Endogenous hypothalamic hormone that stimulates pituitary GH secretion; research analogues include Sermorelin and CJC-1295. GHS-R1a: The ghrelin receptor; the target of GHRP compounds. DAC (Drug Affinity Complex): The maleimide-containing extension of CJC-1295 that enables albumin binding for extended half-life. PEGylation: Covalent attachment of polyethylene glycol chains to extend half-life and reduce immunogenicity. Bioregulator: A short peptide (2-4 amino acids) in the Khavinson research program proposed to regulate gene expression in tissue-specific ways. BAC water: Bacteriostatic water; sterile water containing 0.9% benzyl alcohol preservative used for peptide reconstitution.
Regulatory Terms
RUO (Research Use Only): Designation indicating a compound is intended for in vitro and preclinical research, not human use. IND (Investigational New Drug): FDA application required to begin clinical trials with an investigational compound. IRB (Institutional Review Board): Independent committee that reviews and approves human subjects research. GCP (Good Clinical Practice): International standard for conducting clinical trials. GMP (Good Manufacturing Practice): Quality assurance framework governing pharmaceutical manufacturing conditions. WADA: World Anti-Doping Agency; maintains the Prohibited List of substances banned in competitive sport including many research peptides.
Conclusion
This glossary covers the foundational terminology spanning the full spectrum of research peptide science from synthesis to pharmacology to regulatory context. Building fluency in this vocabulary enables researchers to read literature critically, communicate precisely with colleagues and vendors, and evaluate quality documentation effectively. These 50 terms provide the core vocabulary for confident engagement with research peptide science.