The research reference for peptides

Lab guides

• What is a peptide?

  A peptide is a short chain of amino acids joined by amide bonds. This guide explains how peptides are built, named, modified, made and classified, and how they differ from proteins.

• How to read a peptide certificate of analysis

  A certificate of analysis summarizes the tests run on one lot of peptide. This guide walks through each section of a typical COA, what the numbers mean, and the red flags that suggest the document cannot be relied on.

• Purity vs net peptide content

  HPLC purity and net peptide content answer different questions about a peptide powder. This guide explains what each measures, how they are determined, and how to use them together when preparing solutions of known concentration.

• HPLC and mass spectrometry explained

  HPLC and mass spectrometry are the two core analytical methods for peptides. This guide explains how reversed-phase HPLC separates peptides, how ESI and MALDI mass spectrometry confirm identity, and how LC-MS combines them.

• Endotoxin testing for peptides

  Endotoxins are lipopolysaccharides from Gram-negative bacteria that can distort cell-based and animal experiments. This guide covers LAL gel-clot, turbidimetric and chromogenic methods, recombinant factor C, endotoxin units and how to read results.

• Peptide storage and stability

  Peptides degrade through oxidation, deamidation, aspartimide formation, hydrolysis and aggregation. This guide explains each pathway, which sequences are most at risk, and lab practices for storing lyophilized powder and solutions.

All guides

Comparisons

• BPC-157 vs TB-500

  BPC-157 and TB-500 are unrelated synthetic peptides often discussed together in tissue-repair research. This page compares their origin, structure, proposed mechanisms, evidence base, regulatory status and the analytical issues raised by combined blends.

• Ipamorelin vs CJC-1295

  Ipamorelin is a pentapeptide ghrelin receptor (GHS-R1a) agonist; CJC-1295 is a modified GHRH analogue, in some versions with an albumin-binding DAC group. This page compares their receptors, structures, research history and analytical considerations.

• Selank vs Semax

  Selank and Semax are synthetic heptapeptides developed in Russia, each ending in a Pro-Gly-Pro extension. Selank is a tuftsin analogue studied for anxiety-related effects; Semax is an ACTH(4-10) analogue studied in neurological settings.

• GHK vs GHK-Cu

  GHK is the tripeptide glycyl-L-histidyl-L-lysine; GHK-Cu is the same peptide bound to a copper(II) ion. This page explains how the free peptide and the copper complex differ in structure, research use, analysis and handling.

• Sermorelin vs Tesamorelin

  Sermorelin and tesamorelin are both analogues of growth hormone-releasing hormone. Sermorelin is the 29-residue active fragment and was once FDA-approved; tesamorelin is the full 44-residue sequence with an N-terminal modification and remains FDA-approved as Egrifta.

• Semaglutide vs Tirzepatide vs Retatrutide

  Semaglutide, tirzepatide and retatrutide are lipidated incretin-based peptides with one, two and three receptor targets. Semaglutide and tirzepatide are FDA-approved; retatrutide is investigational. This page compares their mechanisms, structures, trial programs and status.

All comparisons

Research digest

The newest PubMed papers for every compound, refreshed automatically. Browse the digest.

State of peptide quality, 2026

What lab studies, regulator tests and 70,000+ testing records show about identity, purity and contamination. Read the report.

Amino acids

Codes, residue masses, side-chain chemistry and stability notes for all 20. See the table.

Tools

• Peptide sequence analyzer

  Paste a sequence to get molecular formula, average and monoisotopic mass, expected MS ions, isoelectric point, net charge, hydropathy, extinction coefficient and stability flags.

• Peptide reconstitution calculator

  Enter the peptide in the vial and the solvent you add to get the concentration, plus the volume to pipette for the amount your assay needs.

• COA checker

  Check a certificate of analysis: does the reported mass match the compound, is the purity plausible, and is the paperwork complete?

Regulatory tracker