Newest Guides
The latest additions to the library — a new guide is published most days.
What Is Karl Fischer Titration?
How the water content of a freeze-dried peptide is measured — the iodine–sulfur-dioxide reaction that consumes water one-to-one, volumetric versus coulometric titration, and why residual moisture is a critical quality attribute.
Read guide → New QualityEndotoxin Testing Explained
What the bacterial endotoxins test detects and how it works — the horseshoe-crab LAL clotting cascade, the gel-clot, turbidimetric and chromogenic methods, recombinant Factor C, and how an endotoxin result is read in endotoxin units.
Read guide → New Research GuideWhat Is Deamidation?
How asparagine — and, far more slowly, glutamine — spontaneously turns acidic through a cyclic succinimide intermediate, scrambling into aspartate and isoaspartate with a hidden +0.984-dalton mass shift.
Read guide → New ExplainerWhat Is Hydroxylation?
The enzymatic addition of a hydroxyl group to an amino acid — 4-hydroxyproline that stabilises collagen, 5-hydroxylysine, and the HIF prolyl hydroxylation behind oxygen sensing — the iron and 2-oxoglutarate enzymes that install it, and its +16-dalton signature.
Read guide → New Research GuideWhat Is Biotinylation?
How a small biotin tag is attached to a peptide or protein — the amine, thiol and enzymatic routes, the near-unbreakable biotin–streptavidin bond, and what it is used for in affinity capture, detection and proximity labeling.
Read guide → New Research GuideWhat Is Resin in Peptide Synthesis?
The insoluble polymer bead that solid-phase peptide synthesis is built on — what the backbone and linker are, how loading and swelling work, and why Wang, Rink amide and 2-chlorotrityl resins give different C-termini.
Read guide → New Research GuideWhat Is Peptide Cleavage?
The final acid step of solid-phase synthesis — how trifluoroacetic acid (or, in Boc chemistry, hydrogen fluoride) cuts the finished chain from the resin and strips its side-chain protecting groups at once, and why scavengers make up most of the cocktail.
Read guide → New ExplainerWhat Is a Peptidomimetic?
Molecules built to do what a peptide does without its weaknesses — backbone surrogates, peptoids, β-peptides, foldamers, azapeptides and retro-inverso chains, plus the classic drugs (captopril, the HIV protease inhibitors) the idea produced.
Read guide → New ExplainerWhat Is Follistatin 344?
The full-length follistatin precursor — what FS344, FS315 and FS288 mean, how follistatin wraps around activin and myostatin to block their receptors, what the mouse, primate and gene-therapy research studied, and why it is a protein rather than a peptide.
Read guide → New ExplainerWhat Is Tirzepatide?
The 39-amino-acid dual GIP/GLP-1 receptor agonist — how it is built on the GIP sequence, why it is imbalanced toward the GIP receptor and biased at the GLP-1 receptor, what the preclinical and clinical record studied, and where it sits between semaglutide and Retatrutide.
Read guide → New QualityPeptide Impurities Explained
The fraction of a research peptide that is not the target molecule, named and explained — deletion and truncation sequences, aspartimide and epimer by-products, oxidation and deamidation, dimers, counterions and solvents, and how each one is measured.
Read guide → New QualityWhat Is Amino Acid Analysis?
The classic method that measures how much peptide a powder actually contains and what it is made of — acid hydrolysis back to free amino acids, ion-exchange and ninhydrin or pre-column tagging, and why it is the reference behind net peptide content.
Read guide → New Research GuideWhat Is a Protecting Group?
The removable chemical caps that let a peptide be built one bond at a time — Boc, Fmoc, tBu, Trt and Pbf: temporary versus permanent protection, what orthogonality means, and how each group is taken off.
Read guide → New Research GuideWhat Is Native Chemical Ligation?
How two separately made peptides are joined into one — a C-terminal thioester meets an N-terminal cysteine and rearranges into a native peptide bond. The reaction behind chemical protein synthesis, expressed protein ligation and mirror-image proteins.
Read guide → New QualityWhat Is HPLC?
The analysis behind the purity figure on a peptide’s COA — how a reversed-phase column separates a peptide from its impurities, why acetonitrile gradients and trifluoroacetic acid do the work, what UV detection at 214 nm sees, and how a purity percentage is read from peak area.
Read guide → New QualityWhat Is Mass Spectrometry?
The analysis that confirms a peptide’s identity by weighing it — how electrospray and MALDI lift an intact peptide into the gas phase, how an analyzer sorts ions by mass-to-charge, monoisotopic versus average mass, how tandem MS reads a sequence, and why identity is not purity.
Read guide → New ExplainerWhat Is N-Methylation?
The backbone edit that swaps an amide’s N–H for a single methyl group — how it removes a hydrogen-bond donor, bends the chain toward cis bonds and turns, blocks proteases, and adds a clean +14-dalton signature. Why cyclosporine’s seven N-methyls made it the model, and how N-methyl peptides are built.
Read guide → New ExplainerWhat Is Phosphorylation?
The reversible phosphate switch at the centre of cell signalling — how a kinase adds a phosphate to a serine, threonine or tyrosine and a phosphatase takes it off, the phosphoester bond, the +80-dalton mass signature that finds it, and how phosphopeptides are made.
Read guide → New QualityWhat Is Net Peptide Content?
The number that says how much of a peptide powder is actually peptide — not the water, counterions and salt weighed with it — how amino acid analysis and nitrogen measure it, and why it is not the same thing as HPLC purity.
Read guide → New ComparisonFmoc vs Boc Synthesis
The two protecting-group strategies behind solid-phase peptide synthesis — how Fmoc comes off with base and Boc with acid, orthogonal versus graduated acidolysis, the HF-versus-TFA endgame, and why Fmoc/tBu became the industry standard.
Read guide → New ExplainerWhat Is Glycosylation?
How a carbohydrate — a glycan — is attached to a protein: N-linked and O-linked glycosylation, the Asn–X–Ser/Thr sequon, the dolichol pathway and the oligosaccharyltransferase, the dynamic O-GlcNAc mark, and why the sugars come as a spread of glycoforms.
Read guide → New ExplainerWhat Is an Amino Acid?
The single molecule every peptide is built from — the alpha-carbon backbone and the side chain that makes each one different, the twenty standard amino acids, L versus D handedness, the zwitterion, and how they link into chains.
Read guide → New ExplainerWhat Is Peptide Stapling?
How a single synthetic bridge locks a peptide’s α-helix in place — the all-hydrocarbon ring-closing metathesis chemistry, the i,i+4 and i,i+7 staple geometry, the non-natural S5 and R8 amino acids, and what stapling changes about helicity and protease resistance.
Read guide →Research Digest
A weekly, dated watch of new peptide research and regulatory developments.
Start Here & Buying 4
New to research peptides? Begin here — what they are, how to evaluate a vendor, and how to pay.
What Are Peptides?
Brand new to peptides? A plain-English guide that starts from zero and builds to real depth — the biology, the chemistry, how research peptides are made, and the main families studied today.
Read guide → Buyer's GuideHow to Buy Research Peptides
A first-timer's guide: how to vet a vendor, why the COA is everything, what supplies you need, how ordering works, and the red flags to avoid.
Read guide → Payment GuideHow to Pay With Crypto
New to cryptocurrency? A plain-English, 10-minute walkthrough for paying your order with Bitcoin — including how to buy and send it from Robinhood. No experience needed.
Read guide → Buyer's GuidePeptide Sciences Alternative: What to Look For in 2026
How to vet a research peptide vendor after switching — third-party testing, published COAs, — and USA sourcing — and where Patriot Labs fits.
Read guide →Compound Explainers 38
Single-compound guides: what each peptide is, its structure, and how it is studied.
What Is FLGR-242?
A supplier designation marketed as a modified Follistatin 344 — what the manufacturer claims, what follistatin biology actually establishes, why gene-therapy results are not evidence about an injected protein, and what no published study has tested.
Read guide → ExplainerWhat Is Follistatin 344?
The full-length follistatin precursor — what FS344, FS315 and FS288 mean, how follistatin wraps around activin and myostatin to block their receptors, what the mouse, primate and gene-therapy research studied, and why it is a protein rather than a peptide.
Read guide → ExplainerWhat Is Tirzepatide?
The 39-amino-acid dual GIP/GLP-1 receptor agonist — how it is built on the GIP sequence, why it is imbalanced toward the GIP receptor and biased at the GLP-1 receptor, what the preclinical and clinical record studied, and where it sits between semaglutide and Retatrutide.
Read guide → ExplainerWhat Is Acetylation?
The N-terminal cap that mirrors amidation — how an acetyl group on a peptide’s first residue neutralises its charge, how it differs from the lysine acetylation of histones, the NAT enzymes that install it, and the +42-dalton mass signature.
Read guide → ExplainerWhat Is Pentadeca Arginate (PDA)?
Not a new peptide but a salt variant of BPC-157 — the same 15-amino-acid sequence paired with an arginine counterion. What the ‘arginate’ label actually means, why the name appeared only after the FDA’s 2023 Category 2 classification, and how a salt form is confirmed on the bench.
Read guide → ExplainerWhat Is HMG?
Not a single molecule but a urine-derived mixture carrying both FSH and LH activity — its two-arm composition, the hCG that supplies most of that LH activity, the 1949 discovery from postmenopausal urine, and why it is an approved biologic rather than a research peptide.
Read guide → ExplainerWhat Is HCG?
A heterodimeric glycoprotein hormone whose carboxy-terminal peptide gives it an unusually long half-life — the two-subunit structure, the LH/CG receptor mechanism, the 1927 Aschheim-Zondek discovery, and why it is an approved biologic rather than a research peptide.
Read guide → ExplainerWhat Is Selank?
The tuftsin-derived heptapeptide built with the same Pro-Gly-Pro tail as Semax — its immune-peptide parent, the GABA, serotonin and enkephalin pathways studied in animal models, its registered status in Russia, and why it sat out the July 2026 FDA compounding review that its sibling faced.
Read guide → ExplainerWhat Is Semax?
The ACTH(4–7) fragment stabilized with a Pro-Gly-Pro tail and studied for its influence on BDNF, NGF and neurotrophic signaling — without the adrenal steroidogenic activity of the parent hormone. Its registered status in Russia and the July 2026 FDA compounding review.
Read guide → ExplainerWhat Is AOD-9604?
A sixteen-amino-acid fragment of growth hormone’s C-terminus, engineered to keep lipolytic activity while leaving IGF-1 and blood glucose unaffected in the models tested — the disulfide loop, the beta-3-adrenergic mechanism, and the obesity trials.
Read guide → ExplainerWhat Is Kisspeptin-10?
The C-terminal decapeptide of a molecule first found as a cancer metastasis suppressor, then shown to sit above GnRH at the top of the reproductive axis — the KISS1R mechanism, the KNDy pulse generator, and a human research record that runs from IVF labs to brain imaging.
Read guide → ExplainerPeptide vs Drug vs Biologic
Where the legal lines actually fall — the 40-amino-acid rule that splits a peptide from a biologic, why intended use can turn any molecule into a drug, the day insulin changed categories, and what “research use only” does and does not mean.
Read guide → ExplainerWhat Is 5-Amino-1MQ?
Not a peptide — a small-molecule quinolinium that inhibits NNMT. The enzyme, the NAD+ and SAM rationale, the mouse and cell-culture literature, and how thin that literature actually is.
Read guide → ExplainerWhat Is B12?
A cobalt-centred corrinoid and the strangest of the vitamins — the corrin ring, the four cobalamin forms and their axial ligands, the two B12-dependent enzymes, and why the cyanide in cyanocobalamin is trivial.
Read guide → ExplainerWhat Is DSIP?
Delta sleep-inducing peptide — a fifty-year-old puzzle. Named for an EEG association, still without a confirmed receptor, and contested as an endogenous sleep factor.
Read guide → ExplainerWhat Is Epithalon?
The AEDG tetrapeptide and the telomerase claim — what the studies actually showed, who published them, and why telomerase activation is a double-edged target.
Read guide → ExplainerWhat Is FOXO4-DRI?
The all-D retro-inverso peptide built to disrupt the FOXO4–p53 interaction that keeps senescent cells alive — what senescence and SASP are, how the DRI design works, and how thin the follow-up literature still is.
Read guide → ExplainerWhat Is the Glow Blend?
GHK-Cu, BPC-157 and TB-500 in one vial — what each component is studied for, why they’re combined, and what a fixed-ratio stack costs you scientifically.
Read guide → ExplainerWhat Is Glutathione?
A tripeptide built on an unusual gamma peptide bond, and the GSH/GSSG couple that acts as the cell’s redox buffer — biochemistry that is genuinely settled, and a bioavailability question that is not.
Read guide → ExplainerWhat Is KLOW?
The four-peptide blend — KPV, GHK-Cu, TB-500 and BPC-157 — including a proper look at KPV, the component with the least coverage elsewhere.
Read guide → ExplainerWhat Is KPV?
The C-terminal tripeptide of α-MSH — fragment versus parent, MC1R-dependent and -independent signalling, PepT1 transport, and the rodent colitis literature examined honestly.
Read guide → ExplainerWhat Is Melanotan II?
The cyclic lactam analogue of α-MSH designed at Arizona — what cyclisation does to a peptide, why it is broadly non-selective across melanocortin receptors, and what the regulatory record says.
Read guide → ExplainerWhat Is Pinealon?
The Glu-Asp-Arg bioregulator — the framework it comes from, what has genuinely been studied, and an honest look at a very thin literature.
Read guide → ExplainerWhat Is SLU-PP-332?
Not a peptide — a small-molecule pan-agonist of the estrogen-related receptors, studied as an exercise mimetic. What the Burris lab rodent work reported, what the pharmacokinetics limit, and why there is no human data.
Read guide → ExplainerWhat Is SS-31?
The four-residue peptide that concentrates in the inner mitochondrial membrane without depending on membrane potential — the cardiolipin mechanism, the shift away from the antioxidant story, and a trial record with several missed endpoints.
Read guide → ExplainerWhat Is the Wolverine Blend?
BPC-157 and TB-500 together. The companion to our comparison guide: not how they differ, but why they’re studied as a pair — and whether that rationale holds.
Read guide → ExplainerWhat Is CJC-1295?
The long-acting GHRH analog studied for sustained GH and IGF-1 elevation — DAC vs no-DAC, and the Ipamorelin pairing.
Read guide → ExplainerWhat Is Ipamorelin?
The selective GH secretagogue — how the ghrelin-mimetic pathway prompts a "clean" growth-hormone pulse, and why it's paired with CJC-1295.
Read guide → ExplainerWhat Is PT-141?
The melanocortin peptide that works through the brain — how the MC4R pathway sets it apart, and how it differs from Melanotan II.
Read guide → ExplainerWhat Is Tesamorelin?
The GHRH analog with a metabolic twist — how it works and why its research centers on visceral fat and body composition.
Read guide → ExplainerWhat Is Bacteriostatic Water?
What it is, how it differs from sterile and distilled water, why it's used for peptides, how much to add, and how long it lasts once opened.
Read guide → ExplainerWhat Is BPC-157?
The Body Protection Compound explained — the pentadecapeptide studied for tissue repair and blood-vessel formation, and why it's paired with TB-500.
Read guide → ExplainerWhat Is Cagrilintide?
The long-acting amylin analog studied for satiety signaling — a different pathway from GLP-1, and why it's studied alongside Retatrutide.
Read guide → ExplainerWhat Is GHK-Cu?
The copper peptide explained — a tripeptide studied for skin, collagen, and tissue remodeling, and why its decline with age matters.
Read guide → ExplainerWhat Is MOTS-c?
The mitochondrial-derived peptide — encoded in mitochondrial DNA and studied for metabolic regulation across metabolic and longevity research.
Read guide → ExplainerWhat Is NAD+?
The coenzyme at the center of cellular energy — what it does, why levels fall with age, and why it anchors longevity research.
Read guide → ExplainerWhat Is TB-500?
The thymosin beta-4 fragment studied for cell migration and systemic repair — how it works and where it diverges from BPC-157.
Read guide → ExplainerWhat Is Retatrutide?
The GLP-1 / GIP / glucagon triple-receptor agonist explained — how the mechanism works and why the glucagon arm sets it apart.
Read guide →Comparisons 11
Head-to-head guides on closely related research compounds.
Fmoc vs Boc Synthesis
The two protecting-group strategies behind solid-phase peptide synthesis — how Fmoc comes off with base and Boc with acid, orthogonal versus graduated acidolysis, the HF-versus-TFA endgame, and why Fmoc/tBu became the industry standard.
Read guide → ComparisonEpithalon vs Pinealon
Two short Khavinson peptide bioregulators compared — Epithalon, the pineal tetrapeptide AEDG studied for telomerase, and Pinealon, the cortex-derived tripeptide EDR studied for neuroprotection. Sequence, mechanism, research and regulatory status.
Read guide → ComparisonMOTS-c vs SS-31
A structural, mechanistic and regulatory comparison of two mitochondrial peptides — MOTS-c, a peptide encoded by mitochondrial DNA, and SS-31 (elamipretide), a synthetic cardiolipin-binding tetrapeptide.
Read guide → ComparisonIpamorelin vs Tesamorelin
A five-residue ghrelin-mimetic and a full 44-residue GHRH analog compared — the two receptor doors they use, how each resists enzymes, and why only one is an approved drug.
Read guide → ComparisonCJC-1295 vs Ipamorelin
Two growth-hormone secretagogues that do not act at the same receptor — a long-acting GHRH analog and a short, selective ghrelin-receptor agonist. Their structures, the evidence level behind each, why the two pathways are studied together as a blend, and the with-DAC naming tangle.
Read guide → ComparisonAOD-9604 vs GLP-1 Peptides
Two opposite strategies in metabolic research: cut a hormone down to its useful fragment, or engineer a durable agonist for a known receptor. Only one produced approved drugs.
Read guide → ComparisonGHK-Cu vs AHK-Cu
One amino acid apart, with the same copper coordination motif. The real difference isn’t chemistry — it’s decades of literature versus a handful of studies.
Read guide → ComparisonMelanotan II vs PT-141
Two melanocortin peptides from the same POMC family — receptor selectivity, the metabolite relationship between them, and sharply different development histories.
Read guide → ComparisonSemax vs Selank
Two Russian heptapeptides built with the same stabilising trick from completely different parent molecules — and the replication gap they share.
Read guide → ComparisonRetatrutide vs Tirzepatide vs Semaglutide
Single, dual, and triple incretin agonists explained — how many receptors each engages and why receptor coverage is the whole story.
Read guide → ComparisonBPC-157 vs TB-500
Two of the most-studied recovery peptides — how their mechanisms and tissue focus differ, and why they're researched together.
Read guide →Handling, Storage & Procedure 7
Reconstitution, storage, cold chain, and safe handling in a research setting.
How to Reconstitute Research Peptides
A step-by-step guide to reconstituting lyophilized peptides with bacteriostatic water — plus the math for exact concentrations.
Read guide → ProcedureHow to Reconstitute Glutathione
Glutathione is freely soluble but oxidises fast once wet — why gentle technique beats force, whether to shake or warm the solvent, and what a cloudy or yellow vial is telling you.
Read guide → ProcedureHow to Store Research Peptides
Lyophilized vs. reconstituted storage, temperature ranges, and how to avoid freeze-thaw degradation in the lab.
Read guide → ProcedurePeptide Handling Best Practices
Why peptides clump, gel or turn cloudy, how to reconstitute cleanly, what freeze-thaw and age do to stability, and how long lyophilised and reconstituted material actually lasts refrigerated or frozen.
Read guide → ProcedureCold Chain for Research Peptides
Material in motion — what actually degrades peptides in transit, how to inspect a shipment on arrival, and what a collapsed lyophilized cake tells you.
Read guide → ProcedureSharps Handling & Disposal
Container standards, the three-quarter fill rule, why recapping is the classic injury mechanism, and what a needle clipper does and does not do.
Read guide → ProcedureHow to Inject Peptides
A safety-first reference: subcutaneous vs intramuscular, injection sites and rotation, needle gauges and lengths, aseptic technique, and safe sharps disposal.
Read guide →Quality, Testing & COAs 16
Purity grades, counterions, and how to read a certificate of analysis.
What Is a Reference Standard?
The characterized sample of known identity and assigned value that gives every certificate-of-analysis number its meaning — reference material versus certified reference material, how a value is built by mass balance, and primary versus working standards.
Read guide → QualityWhat Is Bioburden Testing?
How laboratories count the viable bacteria, yeasts and moulds on or in a material before sterilization — recovery and enumeration, the TAMC and TYMC counts, recovery efficiency and the correction factor, CFU limits, and how a bioburden count sets a sterilization dose.
Read guide → QualityWhat Is Circular Dichroism?
How CD spectroscopy reads a peptide’s backbone shape from the way it absorbs left- and right-circularly polarized light — the α-helix, β-sheet and coil signatures in the far-UV, and how the spectrum is turned into secondary-structure percentages.
Read guide → QualityResidual Solvent Testing Explained
How static headspace gas chromatography measures the volatile solvents left in a peptide or drug substance — the ICH Q3C three-class framework, permitted daily exposure, the USP <467> procedures, and how a residual-solvent result is read.
Read guide → QualityWhat Is Karl Fischer Titration?
How the water content of a freeze-dried peptide is measured — the iodine–sulfur-dioxide reaction that consumes water one-to-one, volumetric versus coulometric titration, and why residual moisture is a critical quality attribute.
Read guide → QualityEndotoxin Testing Explained
What the bacterial endotoxins test detects and how it works — the horseshoe-crab LAL clotting cascade, the gel-clot, turbidimetric and chromogenic methods, recombinant Factor C, and how an endotoxin result is read in endotoxin units.
Read guide → QualityPeptide Sequencing Explained
How the order of a peptide’s amino acids is determined — Edman degradation reading one residue at a time from the N-terminus, tandem mass spectrometry reconstructing the sequence from fragment masses, and why some residues are hard to tell apart.
Read guide → QualityPeptide Impurities Explained
The fraction of a research peptide that is not the target molecule, named and explained — deletion and truncation sequences, aspartimide and epimer by-products, oxidation and deamidation, dimers, counterions and solvents, and how each one is measured.
Read guide → QualityWhat Is Amino Acid Analysis?
The classic method that measures how much peptide a powder actually contains and what it is made of — acid hydrolysis back to free amino acids, ion-exchange and ninhydrin or pre-column tagging, and why it is the reference behind net peptide content.
Read guide → QualityWhat Is HPLC?
The analysis behind the purity figure on a peptide’s COA — how a reversed-phase column separates a peptide from its impurities, why acetonitrile gradients and trifluoroacetic acid do the work, what UV detection at 214 nm sees, and how a purity percentage is read from peak area.
Read guide → QualityWhat Is Mass Spectrometry?
The analysis that confirms a peptide’s identity by weighing it — how electrospray and MALDI lift an intact peptide into the gas phase, how an analyzer sorts ions by mass-to-charge, monoisotopic versus average mass, how tandem MS reads a sequence, and why identity is not purity.
Read guide → QualityWhat Is Net Peptide Content?
The number that says how much of a peptide powder is actually peptide — not the water, counterions and salt weighed with it — how amino acid analysis and nitrogen measure it, and why it is not the same thing as HPLC purity.
Read guide → QualityHow to Read a Peptide COA
A field-by-field walkthrough of a certificate of analysis — what HPLC purity and mass spectrometry each prove, why purity percent is not peptide content, and how to spot a certificate that was never real.
Read guide → QualityPeptide Purity Grades Explained
Crude, desalted, >95% and >98%: what an HPLC purity number actually measures, why it’s not the same as net peptide content, and what the percentage can’t prove.
Read guide → ReferenceWhich Peptides Gel, and How to Mix Each One
Gelling is not bad luck — it is sequence chemistry meeting concentration. A per-compound reference to which materials in the catalogue are prone to aggregating into a gel or haze, why each behaves the way it does, and the diluent volume that keeps each vial clear.
Read guide → QualityTFA vs Acetate in Peptides
Two vials of the same peptide, same purity, same synthesis, can still differ in one respect that rarely reaches the label — the counterion. Why trifluoroacetate ends up on nearly every synthetic peptide, how it can confound in-vitro work, and how salt form relates to net peptide content on a COA.
Read guide →Research & Science Overviews 49
Deeper chemistry, manufacturing, mechanisms, and best-of research roundups.
What Is Pyroglutamate?
The cyclic pGlu ring that caps a peptide’s front end when an N-terminal glutamine or glutamate closes on itself — the −17 and −18 dalton routes, the glutaminyl cyclase that installs it, and why the sealed terminus blocks Edman sequencing.
Read guide → Research GuideWhat Is Isoaspartate?
The β-aspartate backbone isomer that forms when a succinimide ring opens the wrong way — the extra methylene it threads into the chain, the deamidation and aspartate-isomerization routes behind it, and why it can hide at an unchanged mass.
Read guide → Research GuideWhat Is Methionine Oxidation?
The addition of oxygen to methionine’s sulfur — methionine sulfoxide at +16 daltons and the harsher sulfone at +32 — the oxidants that drive it, the Msr enzymes that reverse it, and the mass and chromatographic signatures that reveal it.
Read guide → Research GuideWhat Is Deamidation?
How asparagine — and, far more slowly, glutamine — spontaneously turns acidic through a cyclic succinimide intermediate, scrambling into aspartate and isoaspartate with a hidden +0.984-dalton mass shift.
Read guide → ExplainerWhat Is Hydroxylation?
The enzymatic addition of a hydroxyl group to an amino acid — 4-hydroxyproline that stabilises collagen, 5-hydroxylysine, and the HIF prolyl hydroxylation behind oxygen sensing — the iron and 2-oxoglutarate enzymes that install it, and its +16-dalton signature.
Read guide → Research GuideWhat Is Biotinylation?
How a small biotin tag is attached to a peptide or protein — the amine, thiol and enzymatic routes, the near-unbreakable biotin–streptavidin bond, and what it is used for in affinity capture, detection and proximity labeling.
Read guide → Research GuideWhat Is Resin in Peptide Synthesis?
The insoluble polymer bead that solid-phase peptide synthesis is built on — what the backbone and linker are, how loading and swelling work, and why Wang, Rink amide and 2-chlorotrityl resins give different C-termini.
Read guide → Research GuideWhat Is Peptide Cleavage?
The final acid step of solid-phase synthesis — how trifluoroacetic acid (or, in Boc chemistry, hydrogen fluoride) cuts the finished chain from the resin and strips its side-chain protecting groups at once, and why scavengers make up most of the cocktail.
Read guide → Research GuideWhat Is Liquid-Phase Peptide Synthesis?
Building peptides in solution instead of on a resin — classical fragment condensation and modern soluble-tag (anchored) synthesis, how it compares with SPPS, and why it underpins greener, large-scale peptide manufacturing.
Read guide → Research GuideWhat Is Racemization?
The synthesis side reaction that flips an amino acid from its natural L form to the mirror-image D — the oxazolone and enolization mechanisms, why histidine and cysteine are worst, the reagents that suppress it, and why a D-isomer weighs the same yet hides on a routine HPLC trace.
Read guide → ExplainerWhat Is Sulfation?
The tyrosine modification that mimics phosphorylation on the scales but does the opposite job — a sulfate added to a tyrosine O-sulfate ester by TPST in the Golgi, the +80-dalton mass it shares with phosphate, the PSGL-1, factor VIII and CCR5 examples, and how sulfopeptides are made.
Read guide → ExplainerWhat Is a Peptidomimetic?
Molecules built to do what a peptide does without its weaknesses — backbone surrogates, peptoids, β-peptides, foldamers, azapeptides and retro-inverso chains, plus the classic drugs (captopril, the HIV protease inhibitors) the idea produced.
Read guide → Research GuidePeptide Coupling Reagents
The reagents that switch on a carboxyl group so the next amino acid will join it — carbodiimides (DIC, DCC), aminium/uronium salts (HBTU, HATU) and phosphonium salts (PyBOP), plus the HOBt, HOAt and Oxyma additives that stop racemization.
Read guide → Research GuideWhat Is a Protecting Group?
The removable chemical caps that let a peptide be built one bond at a time — Boc, Fmoc, tBu, Trt and Pbf: temporary versus permanent protection, what orthogonality means, and how each group is taken off.
Read guide → Research GuideWhat Is Native Chemical Ligation?
How two separately made peptides are joined into one — a C-terminal thioester meets an N-terminal cysteine and rearranges into a native peptide bond. The reaction behind chemical protein synthesis, expressed protein ligation and mirror-image proteins.
Read guide → ExplainerWhat Is N-Methylation?
The backbone edit that swaps an amide’s N–H for a single methyl group — how it removes a hydrogen-bond donor, bends the chain toward cis bonds and turns, blocks proteases, and adds a clean +14-dalton signature. Why cyclosporine’s seven N-methyls made it the model, and how N-methyl peptides are built.
Read guide → ExplainerWhat Is Phosphorylation?
The reversible phosphate switch at the centre of cell signalling — how a kinase adds a phosphate to a serine, threonine or tyrosine and a phosphatase takes it off, the phosphoester bond, the +80-dalton mass signature that finds it, and how phosphopeptides are made.
Read guide → ExplainerWhat Is Glycosylation?
How a carbohydrate — a glycan — is attached to a protein: N-linked and O-linked glycosylation, the Asn–X–Ser/Thr sequon, the dolichol pathway and the oligosaccharyltransferase, the dynamic O-GlcNAc mark, and why the sugars come as a spread of glycoforms.
Read guide → ExplainerWhat Is an Amino Acid?
The single molecule every peptide is built from — the alpha-carbon backbone and the side chain that makes each one different, the twenty standard amino acids, L versus D handedness, the zwitterion, and how they link into chains.
Read guide → ExplainerWhat Is Peptide Stapling?
How a single synthetic bridge locks a peptide’s α-helix in place — the all-hydrocarbon ring-closing metathesis chemistry, the i,i+4 and i,i+7 staple geometry, the non-natural S5 and R8 amino acids, and what stapling changes about helicity and protease resistance.
Read guide → ExplainerWhat Are D-Amino Acids?
The mirror-image (D) forms of the amino acids that build peptides — why the ribosome makes only L-amino acids, where D-residues occur in nature, how a single D-swap resists proteases, retro-inverso peptides, and how a lab tells the two apart.
Read guide → Research GuideCapsules vs Injections vs Nasal Sprays
Why the same peptide is a capsule, an injectable or a nasal spray — the formulation science of each format: why the gut degrades peptides, the enhancer chemistry behind oral delivery, why injectables are the default, and how nasal mucosal delivery works.
Read guide → ExplainerWhat Is a Disulfide Bond?
How two cysteine thiols oxidize into a covalent sulfur–sulfur bridge — the one bond that folds oxytocin, somatostatin and insulin into shape, how it is made and broken, and the minus-two-dalton mass signature that confirms it.
Read guide → ExplainerWhat Is Amidation?
How turning a peptide’s C-terminal carboxyl group into a neutral amide (–CONH₂) changes it — the PAM enzyme and glycine-extended precursors, why it blocks carboxypeptidases and shifts the charge, and how the Rink amide resin builds it in the lab.
Read guide → ExplainerWhat Is a Peptide Bond?
The amide link that joins every amino acid into a chain — how it forms by losing water, why resonance makes it flat and rigid, the trans and cis forms, how stable it is, and how it is built and read in the lab.
Read guide → ExplainerWhat Is Lipidation?
How attaching a fatty acid lets a peptide bind albumin and circulate far longer — the acylation chemistry, the gamma-glutamyl and OEG linkers, the natural forms, and the GLP-1 and insulin examples.
Read guide → Research GuideWhat Is Solid-Phase Peptide Synthesis?
How almost every synthetic peptide is built — one amino acid at a time on resin beads. Merrifield’s method, the deprotect-couple cycle, Fmoc vs Boc, coupling reagents, cleavage, and why long chains are hard.
Read guide → Research GuideHow Peptides Are Made
The complete manufacturing picture — from your body's own DNA and the animal-gland era through solid-phase synthesis, recombinant fermentation, kilogram-scale reactors, purification and lyophilisation, plus what the GLP-1 boom did to global capacity.
Read guide → Research GuideWhere Are Peptides Made?
Where peptides come from — in the body, and in the world’s factories. The countries and companies behind pharmaceutical and research-grade supply, the GLP-1 capacity race, and what “made in USA” can and cannot mean for a vial.
Read guide → Research GuideRecombinant vs Synthetic Peptides
Two ways to make a peptide: grow it in engineered cells, or build it chemically one residue at a time. Where the dividing line falls, what each route can and cannot make, and the different impurities each one leaves behind.
Read guide → ExplainerWhat Is PEGylation?
How attaching a polyethylene glycol chain changes a peptide — why an inert, water-loving polymer slows kidney clearance and shields it from enzymes, the attachment chemistry, linear vs branched PEG, and the trade-offs.
Read guide → ExplainerPeptide Half-Life Extension
Why peptides clear from the blood in minutes — and how lipidation, PEGylation, albumin binding, D-amino acids and cyclisation are used to make them last hours or days instead.
Read guide → ExplainerCyclic Peptides Explained
Why some peptides are made as rings — head-to-tail, disulfide and lactam cyclization, how a ring changes stability, rigidity and binding, and the natural and approved peptides that are rings.
Read guide → Research GuideWhat Is DAC in Peptides?
The Drug Affinity Complex in full — the maleimide–albumin chemistry, why it turns a minutes-long peptide into a days-long one, what it did to CJC-1295, and why DAC compounds are studied alongside a second peptide.
Read guide → ExplainerWhat Is Lyophilization?
Freeze-drying, explained: how subliming ice under vacuum turns a purified peptide solution into a dry, stable cake — the three drying stages, collapse temperature, and residual moisture.
Read guide → Research GuideHow Peptides Degrade
Hydrolysis, deamidation, oxidation, aggregation and freeze-thaw damage — the chemistry underneath every storage rule, and why most degradation is invisible.
Read guide → Research GuidePeptide pH & Mixing
Why pH decides almost everything in solution — isoelectric points and where peptides fall out of solution, the opposing pH optima that make one perfect storage pH impossible, copper peptides as oxidation catalysts, and what actually happens chemically when two peptides share a vial.
Read guide → Research GuideA History of Peptide Drugs
From the isolation of insulin in 1921 to the GLP-1 era — the discoveries, the chemistry that made peptides possible to build, and the regulatory milestones that turned them into an industry.
Read guide → Research GuideWhy Peptides Are Studied in Blends
The attribution problem at the heart of combination research: additive vs synergistic, why fixed-ratio blends need their own evidence, and what co-formulation does to stability.
Read guide → Research GuidePeptides and the HPG Axis
Kisspeptin, HCG and HMG mapped onto the hypothalamic-pituitary-gonadal axis — including why pulsatile signalling sustains it and continuous signalling shuts it down.
Read guide → Research GuidePeptide Research in Europe
BPC-157 came out of the University of Zagreb; thymosin β4’s only multicentre trial ran across Italy and Poland; and Europe writes the rules for how a synthetic peptide must be characterized — the research record behind the peptides the market talks about most, and what it does not establish.
Read guide → Research GuidePeptides in Pets & Animals
The full veterinary landscape — what's actually approved for dogs, cats, horses, livestock and fish, why species sequence decides whether the immune system attacks a peptide, and what the published evidence really shows.
Read guide → Research GuideBest Peptides for Weight Loss Research
The compounds most studied in metabolic and body-weight research — Retatrutide, Cagrilintide, AOD-9604, and MOTS-c — how each works and how they compare.
Read guide → Research GuideBest Peptides for Muscle Growth
The growth-hormone axis explained — Ipamorelin, CJC-1295, Tesamorelin, and BPC-157, how the two secretagogue classes work, and why they're studied together.
Read guide → Research GuideBest Peptides for Healing & Recovery
BPC-157, TB-500, GHK-Cu, and KPV — the peptides most studied for tissue repair and recovery, and why several are researched together.
Read guide → Research GuideBest Peptides for Anti-Aging & Longevity
GHK-Cu, NAD+, Epithalon, MOTS-c, and SS-31 — how the most-studied longevity peptides target different pathways of cellular aging.
Read guide → Research GuidePeptides in Cognition & Sleep Research
Semax, Selank, DSIP and Pinealon — what each is studied for, and the blood-brain barrier problem every claim in this category has to answer.
Read guide → Research GuidePeptides and Hair Loss
What the published literature actually shows for thymosin β4, AHK-Cu, GHK-Cu and BPC-157 in hair-follicle research — the follicle growth cycle, the wound-healing through-line, and how it all compares with the established evidence base.
Read guide → Research GuideWhat Is AHK-Cu?
The other copper tripeptide, in depth — the coordination chemistry that makes copper peptides work, what the 2007 hair follicle study actually found, how it differs from GHK-Cu, and where the evidence runs out.
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