What Are Peptides? A Plain Guide to the Research Peptides UK Labs Buy

Peptides are chains of amino acids, the same building blocks that make proteins, but shorter. That one sentence covers insulin, oxytocin and the lyophilised vials sold to research laboratories, and it hides a century of chemistry.

This guide explains what a peptide is, how the first ones were isolated and then synthesised, how Bruce Merrifield's 1963 method still makes almost every research peptide sold today, why the product is a freeze-dried powder, and how it is stored. It ends with a tour of what UK laboratories order.

A peptide is a short chain of amino acids

An amino acid is a small molecule with an amine group at one end and a carboxylic acid at the other. Join the acid of one to the amine of the next and water is lost; the bond that remains is a peptide bond. Repeat, and a chain grows.

Two amino acids joined make a dipeptide, three a tripeptide, and chains of a few dozen are oligopeptides or polypeptides. The boundary with proteins is a matter of convention rather than chemistry; the review literature puts therapeutic peptides at molecular weights of roughly 500 to 5,000 daltons, which corresponds to chains of a handful to about 50 amino acids (Wang et al., Signal Transduction and Targeted Therapy, 2022).

The order of amino acids is the sequence, and the sequence is the identity. BPC-157 is 15 amino acids in a fixed order; swap two and it is a different molecule with a different mass. That is why the identity test on a lab report is mass spectrometry rather than a glance at the powder.

In the body peptides act mainly as messengers. The BBC's science desk put it simply in 2026: they "act as chemical messengers, helping cells communicate and playing roles in processes including skin health, immune function and hormone regulation" (BBC News, 2026).

The first peptides medicine borrowed

The story starts with insulin, a 51-amino-acid peptide hormone. Frederick Banting isolated it in 1921 at the University of Toronto, it reached patients within a year, and in 1923 it became the first commercial peptide drug (Wang et al., 2022). For the next ninety years it was extracted from animal pancreases, because nobody could make a chain that long from scratch.

Shorter chains came first. In 1953 Vincent du Vigneaud's group at Cornell reported in the Journal of the American Chemical Society "the synthesis of an octapeptide amide with the hormonal activity of oxytocin", the first time a peptide hormone had been built in a flask and shown to work (du Vigneaud et al., JACS, 1953).

Building it in solution took years, because each coupling step had to be purified before the next and losses compounded. Longer chains needed a different idea.

Merrifield's solid phase method, 1963

The idea came from Bruce Merrifield at the Rockefeller Institute. In a paper published on 1 July 1963, "Solid Phase Peptide Synthesis. I. The Synthesis of a Tetrapeptide", he anchored the first amino acid to an insoluble polystyrene resin and then added the rest one at a time (Merrifield, Journal of the American Chemical Society, 1963).

The advantage is in the washing. Because the growing chain is stuck to a solid bead, excess reagents and by-products can be rinsed away between steps with no purification, and the cycle of couple, wash, deprotect, wash can be repeated dozens of times. At the end the finished chain is cleaved from the resin.

Encyclopaedia Britannica records that the method "can be carried out by machine" and proved significant for research on hormones and enzymes and for commercial manufacture (Britannica, Bruce Merrifield). Automated synthesisers followed, and solid phase peptide synthesis, usually shortened to SPPS, is now how almost every research peptide is made.

The modern form uses temporary protecting groups so that only the intended bond forms at each step. Two schemes dominate, named after the group on the amine: Boc, removed with acid, and Fmoc, removed with a mild base (Thermo Fisher Scientific, Peptide Synthesis). Fmoc chemistry is the common choice for the lengths sold to research labs.

The crude product off the resin is then purified by reversed-phase HPLC, and the fraction containing the target is collected. A companion post explains how to read a peptide certificate of analysis, which is where that purification is reported.

Why peptides are sold as freeze-dried powders

A peptide in water is a peptide slowly falling apart. Hydrolysis, oxidation and deamidation all proceed in solution, and the longer the chain the more sites there are to attack. The pharmaceutical answer is to remove the water.

Wei Wang's review of solid protein pharmaceuticals states that "the most commonly used method for preparing solid protein pharmaceuticals is lyophilization (freeze-drying)" (Wang, International Journal of Pharmaceutics, 2000). The solution is frozen, then held under vacuum so the ice sublimes directly to vapour, leaving a dry cake or powder in the bottom of the vial.

The same review is honest about the cost. Freezing and drying are themselves stresses that can denature proteins, and "even after successful lyophilization with a protein stabilizer(s), proteins in solid state may still have limited long-term storage stability". For short peptides the problem is smaller than for large proteins, which is why a research vial of a 15-residue peptide survives the post in a way a vial of an antibody would not.

Lyophilisation is also why the number on a vial is a gross weight: the dried cake contains bound water and counter-ions from purification along with the peptide.

The powder is reconstituted in a laboratory when needed. Bacteriostatic water, sterile water with 0.9% benzyl alcohol, is the usual multi-draw diluent for a research vial that will be sampled over several sessions.

How lyophilised peptides are stored

The clearest published storage expectations come from the US National Cancer Institute's clinical proteomics consortium, CPTAC, which set standards for the synthetic peptides used as mass spectrometry calibrators. Its recommendations say such peptides "would ideally be stable in solution for at least 30 days at 4 °C and for 3 years at -20 °C", and should tolerate repeated freeze-thaw cycles and at least one lyophilisation and redissolving step with less than 3% loss (Hoofnagle et al., Clinical Chemistry, 2016).

Three practical rules follow for a research bench. The dry powder belongs in a freezer at -20°C for long-term storage. The sealed vial should come to room temperature before it is opened, so that moisture from the air does not condense on the cold powder. And once in solution, the clock in the CPTAC guidance, weeks in the fridge rather than years, is the one that applies.

Sequence matters here too. Chains containing cysteine, methionine or tryptophan oxidise more readily; chains with asparagine or glutamine deamidate. A supplier's lab reports describe the batch on the day of testing, which is why the storage conditions after that date are the buyer's responsibility.

What "research peptide" means in the UK

A research peptide is a synthetic peptide sold as a laboratory reagent rather than as a medicine. In UK law the distinction turns on how the product is presented and what it is for, and it is policed by the MHRA under the Human Medicines Regulations 2012; the companion post on how research peptides are regulated and sold in the UK sets that out in full.

The practical consequence for a buyer is that the product has not been assessed by a regulator, so the batch report is the only quality evidence. A uk peptides supplier that publishes a report per batch, holds stock in the UK and makes no claims about effects in people is operating the way the law expects.

LynxLab's catalogue follows that model. Every peptide is tested to 99% purity with the report on its page, orders placed by 6pm are dispatched the same day by Royal Mail Tracked 24, UK delivery is free on every order, and payment is by card, Apple Pay or Google Pay.

What UK labs actually order

At the short end sits the tripeptide. GHK cu is glycyl-histidyl-lysine holding a copper ion, three amino acids and a metal, used in skin and collagen research and blue in the vial because of the copper.

Glutathione is also three amino acids, and a peptide the body makes for itself as its main antioxidant. It appears in oxidative stress and skin research, and a 1500mg vial of glutathione is one of the larger masses on a research shelf precisely because it is so small a molecule.

In the middle are the fragments and analogues of natural hormones. Delta sleep-inducing peptide, isolated in 1977 and nine amino acids long, is sold as dsip peptide for sleep research. BPC-157, the 15-residue sequence from a gastric protein, is the single most asked-about item and bpc 157 uk buyers choose between 5mg, 10mg and 20mg vials.

Some are unusual for where they come from rather than their length. MOTS-c is encoded by mitochondrial DNA rather than the nucleus, which makes it a rarity among peptides and a subject of metabolism and exercise research.

And one popular item is not a peptide at all. NAD+, nicotinamide adenine dinucleotide, is a coenzyme built from two nucleotides, which is why researchers who buy nad+ for cell energy studies will find its lab report uses a different analytical approach from the peptides beside it.

For the full list, the research peptides uk catalogue groups each family with its strengths, prices and batch report.

Frequently asked questions

What are peptides made of?

Amino acids joined end to end by peptide bonds, each formed when the acid group of one amino acid condenses with the amine group of the next. Therapeutic and research peptides usually run from two to about fifty residues and weigh 500 to 5,000 daltons.

Are peptides the same as proteins?

They are made of the same amino acids and the same bonds, and the dividing line is length rather than chemistry. Chains of up to roughly 50 amino acids are called peptides; longer, folded chains are proteins. Insulin at 51 residues sits almost exactly on the boundary.

Why are research peptides sold as powders?

Because peptides degrade in water by hydrolysis, oxidation and deamidation, and freeze-drying removes the water. Lyophilisation is the standard method for solid protein and peptide pharmaceuticals, and the dry cake can be stored for years at -20°C where a solution would last weeks.

How long do lyophilised peptides last?

Guidance for synthetic standard peptides expects stability of about three years at -20°C, and around 30 days at 4°C once in solution. Those figures assume the vial is kept sealed, dry and cold, and allowed to reach room temperature before opening.

Is NAD+ a peptide?

No. NAD+ is a dinucleotide coenzyme, not a chain of amino acids, although it is often sold and studied alongside peptides. Its lab report uses a method suited to a nucleotide rather than a peptide sequence.

Sources

• Therapeutic peptides: current applications and future directions, Wang et al., Signal Transduction and Targeted Therapy, 2022
• The Synthesis of an Octapeptide Amide with the Hormonal Activity of Oxytocin, du Vigneaud et al., Journal of the American Chemical Society, 1953
• Solid Phase Peptide Synthesis. I. The Synthesis of a Tetrapeptide, Merrifield, Journal of the American Chemical Society, 1963
• Bruce Merrifield, Encyclopaedia Britannica
• Peptide Synthesis, Thermo Fisher Scientific Protein Biology Resource Library
• Lyophilization and development of solid protein pharmaceuticals, Wang, International Journal of Pharmaceutics, 2000
• Recommendations for the generation, quantification, storage and handling of peptides used for mass spectrometry-based assays, Hoofnagle et al., Clinical Chemistry, 2016
• Concern over online peptides sale 'loophole', BBC News, 2026