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Top 10 Most-Cited Peptide Studies of All Time

Peptide research has shaped modern medicine in ways that few other scientific fields can match. From the isolation of insulin in 1921 to the GLP-1 receptor agonists now prescribed to millions, a handful of landmark papers have redirected entire branches of biology, pharmacology, and clinical

Peptide research has shaped modern medicine in ways that few other scientific fields can match. From the isolation of insulin in 1921 to the GLP-1 receptor agonists now prescribed to millions, a handful of landmark papers have redirected entire branches of biology, pharmacology, and clinical practice.

This article counts down the ten most influential and highly cited peptide studies ever published. Some of these papers introduced techniques still used in every peptide lab on Earth. Others identified molecules that became blockbuster drugs. A few did both. Together, they tell the story of how short chains of amino acids became one of the most important classes of molecules in medicine.

A note on citations: exact counts vary across databases (Google Scholar, Web of Science, Scopus, Semantic Scholar) and change daily. The figures cited here reflect the best available data at the time of writing and are meant to convey relative impact, not precise rankings.

Table of Contents

  1. Merrifield's Solid-Phase Peptide Synthesis (1963)
  2. Zasloff's "Antimicrobial Peptides of Multicellular Organisms" (2002)
  3. Sanger's Insulin Amino Acid Sequence (1951)
  4. Banting and Best's Discovery of Insulin (1922)
  5. Yalow and Berson's Radioimmunoassay for Insulin (1960)
  6. Zasloff's Discovery of Magainins (1987)
  7. Du Vigneaud's Synthesis of Oxytocin (1953)
  8. The GLP-1 Incretin Papers (1986-1987)
  9. Eng's Discovery of Exendin-4 from Gila Monster Venom (1992)
  10. Hodgkin's Insulin Crystal Structure (1969)

1. Merrifield's Solid-Phase Peptide Synthesis (1963)

Paper: Merrifield, R.B. "Solid Phase Peptide Synthesis. I. The Synthesis of a Tetrapeptide." Journal of the American Chemical Society, 85(14), 2149-2154 (1963).

Citations: ~6,600+ (Crossref)

Why it matters: Before Bruce Merrifield's 1963 paper, synthesizing a peptide was a grueling, multi-week affair. Each amino acid had to be added in solution, purified, and isolated before the next one could be attached. Merrifield's insight was deceptively simple: anchor the growing peptide chain to an insoluble resin bead, add amino acids one at a time, and wash away the excess reagents between steps. No purification of intermediates required.

The paper itself describes only the synthesis of a four-amino-acid peptide, L-leucyl-L-alanylglycyl-L-valine. That modest result belied the revolution it sparked. Within a decade, solid-phase peptide synthesis (SPPS) had been automated, and laboratories worldwide were building peptides that would have been impossible to construct by classical methods. The technique enabled the production of synthetic hormones, enzyme inhibitors, and eventually entire small proteins.

Merrifield received the 1984 Nobel Prize in Chemistry for this work, one of the rare Nobels awarded to a single individual. His 1963 paper remains the fifth most-cited paper in the entire 145-year history of JACS. Nearly every therapeutic peptide on the market today, from semaglutide to synthetic oxytocin, traces its manufacturing lineage back to this six-page publication.

Read the paper: JACS, 1963

2. Zasloff's "Antimicrobial Peptides of Multicellular Organisms" (2002)

Paper: Zasloff, M. "Antimicrobial peptides of multicellular organisms." Nature, 415(6870), 389-395 (2002).

Citations: ~8,100+ (Semantic Scholar)

Why it matters: By 2002, researchers had spent two decades cataloging antimicrobial peptides (AMPs) from frogs, insects, plants, and mammals. What was missing was a unifying framework. Michael Zasloff's Nature review provided exactly that.

The paper opens with a question hiding in plain sight: why is the cornea of the eye almost always free of infection? Why do insects flourish without lymphocytes or antibodies? The answer, Zasloff argued, is that virtually every multicellular organism deploys short, cationic peptides as a first line of defense against bacteria, fungi, viruses, and protozoa. These peptides are ancient, diverse, and remarkably effective.

The review synthesized data from hundreds of studies into a coherent picture of how AMPs work, where they're found, and why antibiotic-resistant bacteria rarely develop resistance to them. It became the single most-cited paper in the antimicrobial peptide field and a standard reference for anyone working on peptide-based alternatives to conventional antibiotics. If you've read about LL-37 or defensins, you've encountered the framework Zasloff built in this paper.

Read the paper: Nature, 2002

3. Sanger's Insulin Amino Acid Sequence (1951)

Paper: Sanger, F. and Tuppy, H. "The amino-acid sequence in the phenylalanyl chain of insulin." Biochemical Journal, 49(4), 463-481 (1951).

Citations: Foundational (textbook-level knowledge; undercounted by modern databases)

Why it matters: In 1951, most biochemists believed that proteins were somewhat amorphous blobs, lacking precise molecular structures. Frederick Sanger proved them wrong. Working with his postdoc Hans Tuppy at Cambridge, Sanger used a combination of partial acid hydrolysis and the chemical reagent 2,4-dinitrofluorobenzene (later called "Sanger's reagent") to determine the complete amino acid sequence of insulin's B chain, all 30 residues.

The companion paper on the A chain followed in 1953, and by 1955, Sanger had published the complete primary structure of bovine insulin, a 51-amino-acid peptide with two disulfide bonds. This was the first protein ever sequenced.

The implications were staggering. If insulin had a defined sequence, then every protein had a defined sequence. This principle became a cornerstone of Francis Crick's sequence hypothesis and, eventually, the central dogma of molecular biology. Sanger received his first Nobel Prize in Chemistry in 1958 for this work (he would win a second in 1980 for DNA sequencing).

Paradoxically, Sanger's insulin papers are not among the highest-cited by raw count in modern databases. The reason: the discovery was so transformative that it became textbook knowledge, assumed rather than cited. No one cites Newton's Principia in a physics paper. Sanger's insulin sequence occupies a similar status in biochemistry.

Read the paper: Biochem J, 1951

4. Banting and Best's Discovery of Insulin (1922)

Paper: Banting, F.G. and Best, C.H. "The internal secretion of the pancreas." Journal of Laboratory and Clinical Medicine, 7, 251-266 (1922).

Citations: Foundational (textbook-level knowledge)

Why it matters: In the spring of 1921, Frederick Banting, a young surgeon with a half-formed hypothesis, and Charles Best, a 21-year-old medical student, began tying off the pancreatic ducts of dogs in a borrowed laboratory at the University of Toronto. Their goal: isolate the mysterious "internal secretion" that regulated blood sugar.

By January 1922, they had a crude pancreatic extract that consistently lowered blood glucose in diabetic dogs. On January 11, 1922, they injected it into Leonard Thompson, a 14-year-old boy dying of Type 1 diabetes. The first attempt caused an allergic reaction. Biochemist James Collip rapidly purified the extract, and a second injection on January 23 worked dramatically. Thompson's blood sugar dropped, his ketones cleared, and he regained weight.

The 1922 paper describing these experiments is arguably the most consequential publication in the history of peptide therapeutics. Before insulin, a Type 1 diabetes diagnosis was a death sentence, usually within months. After insulin, it became a manageable condition. Banting and his supervisor John Macleod received the 1923 Nobel Prize, the fastest-ever Nobel award from discovery to prize.

Insulin has since generated at least four additional Nobel Prizes (Sanger, Hodgkin, Yalow, and the recombinant insulin work), making it the single most Nobel-decorated molecule in history. As a 51-amino-acid peptide, it remains the foundational example of peptide-based therapy.

Read about the discovery: PMC, "The Discovery of Insulin"

5. Yalow and Berson's Radioimmunoassay for Insulin (1960)

Paper: Yalow, R.S. and Berson, S.A. "Immunoassay of endogenous plasma insulin in man." Journal of Clinical Investigation, 39(7), 1157-1175 (1960).

Citations: ~2,300+ (one of the most-cited papers in JCI history)

Why it matters: Rosalyn Yalow and Solomon Berson wanted to measure how much insulin was actually circulating in human blood. The problem: insulin concentrations are vanishingly small, in the picomolar range. No assay in 1960 could detect quantities that tiny.

Their solution was the radioimmunoassay (RIA). The principle: mix radiolabeled insulin with anti-insulin antibodies, then add the patient's blood sample. Unlabeled insulin displaces labeled insulin from the antibodies in proportion to its concentration. Measure the displaced radioactivity, and you know exactly how much insulin was present.

The method worked with extraordinary sensitivity. For the first time, Yalow and Berson could show that Type 1 diabetes involved insulin deficiency while Type 2 diabetes involved insulin resistance with high circulating insulin.

But the RIA's impact extended far beyond insulin. The technique was rapidly adapted to measure virtually any peptide hormone, drug, or biological molecule at trace concentrations. By 2000, "radioimmunoassay" and "immunoassay" accounted for over 350,000 entries in PubMed. Yalow received the 1977 Nobel Prize in Physiology or Medicine (Berson had died in 1972 and was ineligible).

Read the paper: PubMed, 1960

6. Zasloff's Discovery of Magainins (1987)

Paper: Zasloff, M. "Magainins, a class of antimicrobial peptides from Xenopus skin: isolation, characterization of two active forms, and partial cDNA sequence of a precursor." Proceedings of the National Academy of Sciences, 84(15), 5449-5453 (1987).

Citations: ~3,500+ (estimated from multiple databases)

Why it matters: The discovery began with a surgeon's observation. Michael Zasloff, working at the National Institutes of Health, noticed something peculiar about the African clawed frog (Xenopus laevis). After surgery, the frogs were returned to non-sterile aquarium water, yet their wounds almost never became infected. Conventional immunology couldn't explain why.

Zasloff isolated two 23-amino-acid peptides from the frog's skin and named them magainins (from the Hebrew word for "shield"). At low concentrations, these water-soluble, non-hemolytic peptides killed bacteria, fungi, and protozoa by disrupting microbial cell membranes. They derived from a common precursor protein, representing a previously unrecognized class of vertebrate antimicrobial defenses.

The 1987 paper launched the modern field of antimicrobial peptide research. Within a few years, researchers discovered similar peptides in insects, plants, mammals, and virtually every other multicellular organism studied. The total number of identified AMPs now exceeds 1,200. Many are in preclinical or clinical development as alternatives to failing antibiotics.

For readers interested in specific AMPs, our guides on LL-37 and defensins cover two of the best-studied families that were identified in the wake of Zasloff's frog experiment.

Read the paper: PNAS, 1987

7. Du Vigneaud's Synthesis of Oxytocin (1953)

Paper: Du Vigneaud, V., Ressler, C., and Trippett, S. "The sequence of amino acids in oxytocin, with a proposal for the structure of oxytocin." Journal of Biological Chemistry, 205(2), 949-957 (1953).

Citations: ~440+ (direct citations; impact extends through thousands of derivative studies)

Why it matters: Vincent du Vigneaud did something in 1953 that had never been done before: he determined the complete amino acid sequence of a peptide hormone and then synthesized it from scratch. The peptide was oxytocin, a nine-amino-acid molecule produced by the posterior pituitary gland.

Du Vigneaud's group isolated oxytocin, established that it contained a disulfide bridge between two cysteine residues forming a six-membered ring, and identified the precise order of all nine amino acids. They then chemically synthesized the peptide and demonstrated that the synthetic version was biologically identical to the natural hormone, stimulating uterine contractions and milk ejection with the same potency.

This was the first total synthesis of any peptide hormone, and it carried two major implications. First, it proved that biological activity resided in a specific chemical structure, not in some mysterious "vital force." Second, it demonstrated that hormones could be manufactured, a principle that underpins the entire pharmaceutical peptide industry today.

Du Vigneaud received the 1955 Nobel Prize in Chemistry. Synthetic oxytocin (Pitocin) is now on the WHO's List of Essential Medicines and is used in virtually every hospital on Earth to induce labor and manage postpartum hemorrhage. It remains one of the most widely administered peptide drugs in history.

Read the paper: PubMed, 1953

8. The GLP-1 Incretin Papers (1986-1987)

Key Papers:

  • Mojsov, S., Heinrich, G., Wilson, I.B., Ravazzola, M., Orci, L., and Habener, J.F. "Preproglucagon gene expression in pancreas and intestine diversifies at the level of post-translational processing." Journal of Biological Chemistry, 261(25), 11880-11889 (1986).
  • Mojsov, S., Weir, G.C., and Habener, J.F. "Insulinotropin: glucagon-like peptide I (7-37) co-encoded in the glucagon gene is a potent stimulator of insulin release in the perfused rat pancreas." Journal of Clinical Investigation, 79(2), 616-619 (1987).
  • Kreymann, B., Williams, G., Ghatei, M.A., and Bloom, S.R. "Glucagon-like peptide-1 7-36: a physiological incretin in man." Lancet, 2(8571), 1300-1304 (1987).
  • Holst, J.J., Orskov, C., Nielsen, O.V., and Schwartz, T.W. "Truncated glucagon-like peptide I, an insulin-releasing hormone from the distal gut." FEBS Letters, 211(2), 169-174 (1987).

Citations: Collectively thousands across the four papers

Why it matters: These four papers, published within an 18-month window, established glucagon-like peptide-1 (GLP-1) as a major hormone regulating insulin secretion. Together, they represent one of the most consequential clusters of discoveries in endocrinology.

The story began in 1986, when peptide chemist Svetlana Mojsov and molecular biologist Joel Habener at Massachusetts General Hospital showed that the glucagon gene encoded a second bioactive peptide in the intestine: GLP-1(7-37). In 1987, Mojsov, Habener, and collaborator Gordon Weir demonstrated that tiny amounts of this peptide dramatically stimulated insulin release from the rat pancreas.

Simultaneously, Jens Holst's group in Copenhagen identified a truncated form of GLP-1 from the pig gut with the same insulin-releasing properties. And Stephen Bloom's team in London published a Lancet paper showing that GLP-1(7-36) was a "physiological incretin" in humans, more potent at triggering insulin release than any previously known gut hormone.

The clinical translation of these findings has been nothing short of revolutionary. GLP-1 receptor agonists, including semaglutide (Ozempic/Wegovy), liraglutide, and tirzepatide, now represent a drug class generating over $50 billion in annual revenue. They've transformed the treatment of Type 2 diabetes and obesity, and emerging research shows benefits for cardiovascular disease, kidney disease, neurodegeneration, and addiction.

Habener and Mojsov received the 2024 Lasker Clinical Medical Research Award for their discovery.

Read a key paper: Kreymann et al., Lancet, 1987 | Mojsov et al., JCI, 1987

9. Eng's Discovery of Exendin-4 from Gila Monster Venom (1992)

Paper: Eng, J., Kleinman, W.A., Singh, L., Singh, G., and Raufman, J.P. "Isolation and characterization of exendin-4, an exendin-3 analogue, from Heloderma suspectum venom." Journal of Biological Chemistry, 267(11), 7402-7405 (1992).

Citations: Widely cited as the foundational paper for the entire GLP-1 receptor agonist drug class

Why it matters: In 1992, endocrinologist John Eng at the VA Medical Center in the Bronx was studying Gila monster venom, searching for peptides that might affect the digestive system. He isolated a 39-amino-acid peptide he called exendin-4. It shared 53% of its sequence with human GLP-1 but had one critical advantage: it resisted degradation by dipeptidyl peptidase-4 (DPP-4), the enzyme that normally breaks down GLP-1 in minutes.

When Eng tested exendin-4 in diabetic mice, it lowered blood glucose effectively and for hours, far longer than native GLP-1. The peptide was a natural GLP-1 receptor agonist with built-in pharmacological staying power.

This discovery led directly to exenatide (Byetta), approved by the FDA in 2005 as the first GLP-1 receptor agonist for Type 2 diabetes. But the real legacy is what came next. Pharmaceutical companies used exendin-4 as proof of concept that a long-acting GLP-1 agonist was viable, spurring the development of liraglutide, semaglutide, tirzepatide, and the entire generation of GLP-1 drugs now reshaping metabolic medicine. A lizard's venom leading to drugs that treat millions is one of the most remarkable stories in drug discovery, and a powerful argument for biodiversity conservation.

Read the paper: PubMed, 1992

10. Hodgkin's Insulin Crystal Structure (1969)

Paper: Adams, M.J., Blundell, T.L., Dodson, E.J., Dodson, G.G., Vijayan, M., Baker, E.N., Harding, M.M., Hodgkin, D.C., Rimmer, B., and Sheat, S. "Structure of Rhombohedral 2 Zinc Insulin Crystals." Nature, 224, 491-495 (1969).

Citations: Foundational (extensively cited across structural biology)

Why it matters: Dorothy Crowfoot Hodgkin began taking X-ray photographs of insulin crystals in 1934, just four years after the hormone's crystallization. She wouldn't solve the structure for another 35 years. The challenge was unprecedented: insulin contains 788 atoms distributed across 51 amino acids, arranged in a complex quaternary structure stabilized by zinc ions and disulfide bonds.

In 1969, Hodgkin and her team finally published the 2.8-angstrom resolution electron density map of rhombohedral 2-zinc insulin crystals. The structure revealed that insulin monomers fold into a two-layered sandwich, with the B chain overlaying the A chain. Six monomers assemble around two zinc ions to form a hexamer, the storage form found in pancreatic beta cells.

This was one of the most complex protein structures ever determined at the time. It required analyzing over 70,000 X-ray reflections, a computational feat achieved without modern computers for much of the project.

The clinical implications were enormous. Understanding insulin's three-dimensional structure allowed pharmaceutical scientists to engineer insulin analogs with modified absorption profiles, creating the rapid-acting and long-acting insulins that now allow millions of diabetics to manage their blood sugar with precision. Without Hodgkin's structure, modern insulin therapy would not exist in its current form.

Hodgkin had already received the 1964 Nobel Prize in Chemistry for her earlier crystallographic work on penicillin and vitamin B12. The insulin structure, published five years after her Nobel, remains the crowning achievement of her career. She is the only British woman ever to win a Nobel Prize in the sciences.

Read the paper: Nature, 1969

Honorable Mentions

Several other peptide studies narrowly missed this list but deserve recognition:

  • Steiner, Hultmark, Engstrom, Bennich, and Boman (1981): "Sequence and specificity of two antibacterial proteins involved in insect immunity," published in Nature. This paper identified cecropins A and B from silk moth hemolymph, launching the study of insect antimicrobial peptides. Nature, 1981

  • Fosgerau and Hoffmann (2015): "Peptide therapeutics: current status and future directions," in Drug Discovery Today. With over 2,100 citations, this review mapped the entire peptide drug market at a moment when the field was accelerating. PubMed, 2015

  • Steiner, Cunningham, Spigelman, and Aten (1967): The discovery of proinsulin and C-peptide, which established that insulin is synthesized as a single-chain precursor. This work founded the entire field of protein precursor processing.

  • Hancock and Sahl (2006): "Antimicrobial and host-defense peptides as new anti-infective therapeutic strategies," in Nature Biotechnology. A highly cited review that framed AMPs as both direct antibiotics and immune modulators. Nature Biotechnology, 2006

  • Sikiric et al. (1993): The foundational work on BPC-157, a 15-amino-acid gastric pentadecapeptide with broad protective effects across multiple organ systems. Predrag Sikiric's research group has driven nearly all subsequent BPC-157 studies.

  • Pickart (1973): The isolation of GHK-Cu, a tripeptide copper complex from human plasma that promotes tissue regeneration and influences over 4,000 human genes. The original discovery came from Loren Pickart's Ph.D. thesis at UCSF.

The Bottom Line

These ten studies span nearly a century, from Banting and Best's crude pancreatic extracts in 1922 to the GLP-1 research that produced some of the best-selling drugs of the 2020s. They cover synthesis techniques, hormone discovery, structural biology, innate immunity, and drug development. Yet they share a common thread: each one redefined what peptides could do and what we could do with them.

A few patterns stand out. First, the gap between discovery and clinical application can be long. Hodgkin spent 35 years solving insulin's structure. The GLP-1 papers of 1986-1987 didn't produce an approved drug until 2005, and their full clinical impact didn't arrive until the 2020s with semaglutide. Second, peptide breakthroughs tend to cascade. Sanger's sequencing enabled Merrifield's synthesis, which enabled the manufacturing of every therapeutic peptide that followed. Third, curiosity-driven research in unexpected organisms (frog skin, Gila monster venom, silk moth blood) can yield transformative medicines.

For anyone looking to go deeper into peptide science, our guide to reading peptide research explains how to evaluate the studies cited above and the thousands that have built on them.

The peptide story isn't over. With over 80 peptide drugs approved worldwide, more than 150 in clinical trials, and AI-driven peptide design accelerating the pace of discovery, the next decade's most-cited peptide paper may already be in preparation.

References

  1. Merrifield, R.B. "Solid Phase Peptide Synthesis. I. The Synthesis of a Tetrapeptide." J. Am. Chem. Soc. 85(14), 2149-2154 (1963). https://pubs.acs.org/doi/10.1021/ja00897a025

  2. Zasloff, M. "Antimicrobial peptides of multicellular organisms." Nature 415(6870), 389-395 (2002). https://www.nature.com/articles/415389a

  3. Sanger, F. and Tuppy, H. "The amino-acid sequence in the phenylalanyl chain of insulin. I." Biochem. J. 49(4), 463-481 (1951). https://pmc.ncbi.nlm.nih.gov/articles/PMC1197535/

  4. Banting, F.G. and Best, C.H. "The internal secretion of the pancreas." J. Lab. Clin. Med. 7, 251-266 (1922).

  5. Yalow, R.S. and Berson, S.A. "Immunoassay of endogenous plasma insulin in man." J. Clin. Invest. 39(7), 1157-1175 (1960). https://pubmed.ncbi.nlm.nih.gov/13846364/

  6. Zasloff, M. "Magainins, a class of antimicrobial peptides from Xenopus skin." Proc. Natl. Acad. Sci. USA 84(15), 5449-5453 (1987). https://www.pnas.org/doi/10.1073/pnas.84.15.5449

  7. Du Vigneaud, V., Ressler, C., and Trippett, S. "The sequence of amino acids in oxytocin, with a proposal for the structure of oxytocin." J. Biol. Chem. 205(2), 949-957 (1953). https://pubmed.ncbi.nlm.nih.gov/13129273/

  8. Mojsov, S., Weir, G.C., and Habener, J.F. "Insulinotropin: glucagon-like peptide I (7-37) co-encoded in the glucagon gene is a potent stimulator of insulin release in the perfused rat pancreas." J. Clin. Invest. 79(2), 616-619 (1987). https://pmc.ncbi.nlm.nih.gov/articles/PMC424347/

  9. Kreymann, B., Williams, G., Ghatei, M.A., and Bloom, S.R. "Glucagon-like peptide-1 7-36: a physiological incretin in man." Lancet 2(8571), 1300-1304 (1987). https://pubmed.ncbi.nlm.nih.gov/2890903/

  10. Holst, J.J., Orskov, C., Nielsen, O.V., and Schwartz, T.W. "Truncated glucagon-like peptide I, an insulin-releasing hormone from the distal gut." FEBS Lett. 211(2), 169-174 (1987).

  11. Eng, J., Kleinman, W.A., Singh, L., Singh, G., and Raufman, J.P. "Isolation and characterization of exendin-4, an exendin-3 analogue, from Heloderma suspectum venom." J. Biol. Chem. 267(11), 7402-7405 (1992). https://pubmed.ncbi.nlm.nih.gov/1559982/

  12. Adams, M.J., Blundell, T.L., Dodson, E.J., et al. "Structure of Rhombohedral 2 Zinc Insulin Crystals." Nature 224, 491-495 (1969). https://www.nature.com/articles/224491a0

  13. Steiner, H., Hultmark, D., Engstrom, A., Bennich, H., and Boman, H.G. "Sequence and specificity of two antibacterial proteins involved in insect immunity." Nature 292, 246-248 (1981). https://www.nature.com/articles/292246a0

  14. Fosgerau, K. and Hoffmann, T. "Peptide therapeutics: current status and future directions." Drug Discov. Today 20(1), 122-128 (2015). https://pubmed.ncbi.nlm.nih.gov/25450771/

  15. Hancock, R.E.W. and Sahl, H.G. "Antimicrobial and host-defense peptides as new anti-infective therapeutic strategies." Nat. Biotechnol. 24(12), 1551-1557 (2006). https://www.nature.com/articles/nbt1267

  16. Mojsov, S., Heinrich, G., Wilson, I.B., et al. "Preproglucagon gene expression in pancreas and intestine diversifies at the level of post-translational processing." J. Biol. Chem. 261(25), 11880-11889 (1986).