Peptide Fundamentals: Structure, Synthesis, and Research Classification

What Is a Peptide?

A peptide is a short chain of amino acids linked by amide (peptide) bonds. Peptides occupy a structural space between small molecules and full proteins — generally defined as chains of roughly 2 to 50 amino acid residues, though the boundary with small proteins is not strict. Research peptides span a wide range of biological roles: signaling molecules (hormones, neuropeptides), structural fragments, and synthetic analogs of naturally occurring sequences.

How Research Peptides Are Synthesized

The overwhelming majority of research-grade peptides, including every product in this catalog, are produced by solid-phase peptide synthesis (SPPS), a method developed by Robert Bruce Merrifield in the 1960s (for which he received the 1984 Nobel Prize in Chemistry). SPPS builds a peptide chain one amino acid at a time on an insoluble resin support, allowing excess reagents to be washed away between coupling steps. After synthesis, the peptide is cleaved from the resin, purified — typically by reverse-phase high-performance liquid chromatography (HPLC) — and lyophilized (freeze-dried) into a stable powder form for storage and shipping.

Reading a Peptide Specification Sheet

Every product page in our catalog includes a standardized specification block. Here is what each field means:

• Sequence — the linear order of amino acids, typically abbreviated using three-letter or single-letter codes (e.g., Gly-Glu-Pro for Glycine-Glutamate-Proline).
• CAS number — a unique numeric identifier assigned by the Chemical Abstracts Service, used to unambiguously identify a specific chemical substance across databases and regulatory contexts.
• Molecular formula and molecular weight — the atomic composition and calculated mass of the compound, used to verify identity via mass spectrometry.
• Purity — typically expressed as a percentage determined by HPLC peak-area analysis, indicating what fraction of the sample is the target compound versus synthesis byproducts or residual solvents.
• Form — the physical state as supplied, almost always a lyophilized powder for the compounds in this catalog.

Peptide Classification in This Catalog

We group our catalog into four broad research categories, each covered in a dedicated overview article:

• Growth Hormone Axis peptides — GHRH analogs and GH secretagogues studied for their role in the growth hormone/IGF-1 signaling pathway.
• Repair & Recovery peptides — compounds studied in tissue repair, wound healing, and angiogenesis models.
• Nootropic peptides — CNS-active peptides studied for cognitive and anxiolytic research applications.
• Metabolic & Longevity peptides — compounds studied in the context of cellular metabolism, mitochondrial function, and aging biology.

Verifying Identity and Purity

Because peptide synthesis can introduce truncated sequences, diastereomers, or incomplete deprotection byproducts, independent verification matters. See our guide to COA documentation and purity testing for how we characterize every batch, and our storage and handling guidance for maintaining sample integrity after receipt.

All content on this page describes general peptide chemistry and research classification. It does not constitute dosing, administration, or clinical guidance. Peptide Factory products are supplied for research use only — not for human consumption.