What is a peptide?

A peptide is a short chain of amino acids linked together by peptide bonds. Amino acids are the same building blocks that make proteins, but peptides are shorter often in the range of 5 to 30 amino acids for many research applications.

Step 1 — Designing the sequence

Everything starts with the order of amino acids (the “sequence”). Even a single change can alter solubility, stability, or activity.

Example (simplified):
H–Tyr–Gly–Gly–Phe–Leu–OH

At this stage, chemists often anticipate “trouble spots” (difficult couplings, aggregation, or sequences that benefit from double coupling, longer reaction times, or different solvents).

Step 2 — Solid-Phase Peptide Synthesis (SPPS)

Most modern peptides are made by solid-phase peptide synthesis, where the growing peptide is built while attached to an insoluble resin bead. This makes washing easy: add reagent → react → wash away excess → repeat.

The core loop

Common equipment

• Automated peptide synthesizer (or manual reaction vessel with filtration)
• Vacuum manifold / fritted vessels for efficient washing
• Agitation (shaker or recirculation) and inert gas supply
• Controlled temperature options for tough sequences

Step 3 — Cleavage from resin

When assembly is complete, the peptide is still attached to the resin and often has side chain protections still in place. A cleavage step releases the peptide and removes protecting groups, producing a crude peptide.

“Crude” means it contains a mixture: desired peptide + truncated sequences + side products. It’s not yet distribution-grade.

Step 4 — Purification (typically RP-HPLC)

To isolate the target peptide, labs commonly use reverse phase HPLC. The crude material is dissolved and run through a column (often C18), and fractions are collected as peaks elute.

• Main peak is often the target peptide
• Smaller peaks correspond to impurities or deletions
• Fractions are tested and pooled based on identity/purity

Step 5 — Analytical confirmation

Before drying and filling, labs confirm identity and purity using a combination of:

• Analytical HPLC (purity profile)
• Mass spectrometry (molecular weight confirmation)

This is the quality checkpoint: confirming the correct mass and verifying that impurities are within spec for the intended grade.

Step 6 — Lyophilization (freeze drying)

The familiar “white puck” appears after lyophilization. The peptide is frozen in a vial and then dried under vacuum so ice sublimates directly into vapor (skipping the liquid phase).

• Improves stability for storage and shipping
• Reduces hydrolysis and other solution-phase degradation pathways
• Creates a dry, accurately measurable material for later reconstitution

Step 7 — Sealing, labeling, and distribution

After lyophilization, vials are stoppered and sealed. Labels typically include the peptide identifier, quantity, lot number, and storage guidance. From there, material is packaged for distribution to research teams and end users.