Peptides Guide is a free educational resource dedicated to one of biochemistry's most fascinating families of molecules — peptides. From the venom of a cone snail to the hormones controlling your hunger, peptides are everywhere.
Peptides Guide is an educational reference website dedicated to peptides — the short chains of amino acids that act as hormones, antibiotics, neurotransmitters, and toxins in every living organism. The project is designed as a comprehensive and accessible resource for students, researchers, and anyone interested in biochemistry, pharmacology, and the molecular sciences.
We provide structured, well-researched content covering peptide chemistry, biology, natural history, and the history of peptide science. Alongside reference articles, the site offers original interactive tools — a molecular weight calculator, isoelectric point calculator, hydrophobicity plotter, notation converter, and a curated database of 89+ biologically significant peptides — all running locally in the browser.
Our goal is to present peptides not only as abstract biochemical entities, but as molecules with rich stories and remarkable real-world connections — from the snail toxin that became a painkiller 1,000× more potent than morphine, to the lizard saliva peptide that inspired a new class of diabetes drugs.
Peptides Guide is a project of professional chemists from Aurora Fine Chemicals, LLC and Exclusive Chemistry Ltd — organisations with deep expertise in peptide synthesis and structure-activity relationships.
We also extend thanks to the Chemazone project team for their contribution to the database infrastructure.
Residue masses are computed from IUPAC/CIAAW atomic weights (2021 revision). Charge and pI use the consensus side-chain pKa set (Asp 3.65, Glu 4.25, His 6.00, Cys 8.18, Tyr 10.07, Lys 10.53, Arg 12.48; N-terminus 8.0, C-terminus 3.1). Pace et al. (2009) Protein Science report a partly different set measured in folded proteins, differing by roughly 0.1–0.3 pI units for Cys- and His-rich sequences. Extinction coefficients follow Pace et al. (1995) Protein Science. The Kyte-Doolittle scale follows the original 1982 J. Mol. Biol. publication.
Biological descriptions and natural history content are sourced from peer-reviewed literature. Key sources include Olivera & Teichert (2007) for conotoxins, Zasloff (1987) for magainins, Ling et al. (2015, Nature) for teixobactin, and Vollrath & Knight (2001, Nature) for spider silk. We welcome corrections — if you spot a factual error, please contact us.
What distinguishes this site from most peptide references is the set of original interactive tools built specifically for it. These are not embeds or third-party widgets — each was developed from scratch, runs entirely in the browser, and sends no data to any server.
Enter any peptide sequence to calculate average and monoisotopic molecular weight, elemental formula, net charge at pH 7.4, isoelectric point, and extinction coefficient at 280 nm. Includes batch mode for multiple sequences.
Calculates the isoelectric point and plots the full pH-charge curve from pH 0 to 14. An interactive slider lets you explore net charge at any pH. Each ionizable group is broken down in a table showing pKa and fractional charge.
Plots the Kyte-Doolittle hydrophobicity profile using a sliding window average. Window sizes from 3 to 19 — window 19 activates transmembrane helix prediction (threshold 1.8). Hover over any position for per-residue scores.
Converts between 1-letter and 3-letter amino acid notation. Supports multiple output formats including H-…-OH (explicit termini), dashes, spaces, and concatenated. Converts in both directions.
A curated, searchable reference of 89+ biologically significant peptides. Filter by type (hormone, neuropeptide, antimicrobial, venom, food) or organism source. Click any row to expand details and link directly to the calculators.
A seven-chapter natural history of peptides: venoms (cone snails, scorpions, Gila monster), amphibian skin chemistry, spider silk, marine organisms, bacterial antibiotics, insect venoms (bee, wasp, bullet ant), and fungal peptides. Each chapter cites primary literature.
Anyone curious about chemistry and biology — no prior knowledge required. We write for the kind of person who enjoys learning things in depth and finds the history of science as interesting as the science itself. If you've ever wondered why bee stings hurt differently from nettle stings, how a soil bacterium gave us a transplant drug that saves thousands of lives per year, or what the first ocean-derived drug does in the body, this site was made for you.
The site focuses on chemistry, molecular biology, natural history, and the history of peptide science — framed for general scientific interest. It does not provide medical or dietary advice of any kind.
All chemistry, data, and historical claims are researched against primary sources and peer-reviewed literature.
We translate complex biochemistry into plain language without sacrificing accuracy or depth.
This site is for educational purposes only and does not provide medical, clinical, or dietary advice of any kind.
Peptides Guide is an educational and scientific reference resource. All content is provided for informational and educational purposes only.
Nothing on this website constitutes medical advice, a diagnosis, or a recommendation for treatment. The tools are designed for educational exploration, not clinical use. Always consult a qualified healthcare professional for medical decisions.
Computational results (MW, pI, hydrophobicity) are theoretical estimates. Actual experimental values may differ due to modifications, structural effects, and solution conditions.
Questions, corrections, or suggestions? We welcome corrections — if you spot a factual error, please let us know and we'll address it promptly.