Peptide Fragments & Analogs
Reference guide to peptide fragments, synthetic analogs, modified versions, and blend formulations — understanding how structural modifications change biological activity.
Peptide Fragments & Analogs
Many research peptides are fragments of larger proteins or synthetic analogs designed to isolate specific biological activities, improve stability, or enhance bioavailability. This category catalogs the relationships between parent molecules and their derivatives.
Complete Peptide Directory
Growth Hormone Fragments
| Peptide | Parent Molecule | Modification | Research Focus |
|---|---|---|---|
| HGH Fragment 176-191 | Human Growth Hormone | C-terminal fragment (residues 176-191) | Fat metabolism without GH's growth-promoting effects |
| AOD-9604 | HGH Fragment 176-191 | Stabilized analog with tyrosine addition | Fat metabolism, osteoarthritis (TGA-approved in Australia) |
Thymosin Beta-4 Fragments
| Peptide | Parent Molecule | Modification | Research Focus |
|---|---|---|---|
| TB-500 | Thymosin Beta-4 | Active fragment containing actin-binding domain | Wound healing, cardiac repair, anti-inflammatory |
| TB-4 Frag | Thymosin Beta-4 | N-terminal fragment (Ac-SDKP) | Anti-fibrotic, anti-inflammatory, cardiovascular |
| Thymosin Beta-4 Sulfoxide | Thymosin Beta-4 | Methionine oxidation product | Distinct anti-inflammatory profile, glucocorticoid-like effects |
Alpha-MSH Fragments & Melanocortin Analogs
| Peptide | Parent Molecule | Modification | Research Focus |
|---|---|---|---|
| Alpha-MSH | POMC | Endogenous melanocortin peptide (13 amino acids) | Pigmentation, anti-inflammatory, appetite regulation |
| KPV | Alpha-MSH | C-terminal tripeptide (residues 11-13) | Anti-inflammatory, IBD, NF-kB inhibition |
| PT-141 (Bremelanotide) | Melanotan 2 | Cyclic heptapeptide; MT-2 metabolite | Sexual dysfunction (FDA-approved as Vyleesi) |
| Melanotan 2 | Alpha-MSH | Cyclic analog; non-selective melanocortin agonist | Tanning, sexual function |
| Melanotan 1 | Alpha-MSH | Linear analog; selective MC1R agonist | Photoprotection, EPP |
| MT-II Fragment | Melanotan 2 | Fragment of cyclic melanocortin analog | Isolated melanocortin activity research |
IGF-1 Analogs
| Peptide | Parent Molecule | Modification | Research Focus |
|---|---|---|---|
| IGF-1 | Endogenous | Recombinant full-length | Growth, anabolic effects, neuroprotection |
| IGF-1 DES | IGF-1 | Truncated (lacks first 3 amino acids) | Reduced IGFBP binding; enhanced local tissue effects |
| IGF-1 LR3 | IGF-1 | Arg3 substitution + 13-aa N-terminal extension | Greatly reduced IGFBP binding; extended half-life |
| Long R3 IGF-1 | IGF-1 | Full-length modified for prolonged activity | Prolonged IGF-1 receptor activation |
GHRH Analogs
| Peptide | Parent Molecule | Modification | Research Focus |
|---|---|---|---|
| Sermorelin | GHRH(1-44) | Truncated to first 29 amino acids | GH secretion, anti-aging |
| CJC-1295 | GHRH analog | Modified residues for protease resistance | Extended GH release, body composition |
| CJC-1295 DAC | CJC-1295 | Drug Affinity Complex (albumin-binding) | Ultra-long half-life GH stimulation |
| Tesamorelin | GHRH(1-44) | Trans-3-hexenoic acid modification | HIV lipodystrophy (FDA-approved), visceral fat |
ACTH Fragments
| Peptide | Parent Molecule | Modification | Research Focus |
|---|---|---|---|
| Semax | ACTH(4-10) | C-terminal Pro-Gly-Pro extension | Nootropic, neuroprotective, BDNF modulation |
| Selank | Tuftsin | C-terminal Pro-Gly-Pro extension | Anxiolytic, immunomodulatory, GABA modulation |
Cell Cycle & Senescence Peptides
| Peptide | Description | Research Focus |
|---|---|---|
| ARA-290 | Non-hematopoietic EPO derivative targeting the innate repair receptor | Neuropathic pain, tissue repair without erythropoietic effects |
| B7-33 | Single-chain relaxin-2 analog | Relaxin receptor agonist; anti-fibrotic; cardiovascular |
| P21 Peptide | CNTF-derived peptide for neurogenesis | Hippocampal neurogenesis; cognitive enhancement |
| P21-CDK5 | CDK5 inhibitory peptide based on p35 | CDK5 inhibition; neuroprotection; tau phosphorylation |
| P16 Inhibitor Peptide | Peptide targeting p16INK4a tumor suppressor | Senescence modulation; cell cycle regulation |
Common Research Themes
Fragment Advantage: Fragments often isolate a desired biological activity from the parent molecule while eliminating unwanted effects. HGH Fragment 176-191 retains fat metabolism without growth-promoting activity; KPV retains anti-inflammatory effects without melanocortin tanning.
Stability Modifications: PEGylation (PEG-MGF), DAC conjugation (CJC-1295 DAC), N-acetylation, and amidation are common modifications to extend half-life and improve bioavailability of peptides that would otherwise be rapidly degraded.
Synergistic Blending: Blend formulations combine peptides with complementary mechanisms. The most studied synergy is GHRH + GHRP combinations, where GHRH analogs amplify GH pulse amplitude while GHRPs increase pulse frequency.
Getting Started
If you are new to this category, we recommend starting with CJC-1295 / Ipamorelin Blend — the most popular research combination, pairing GHRH and ghrelin receptor pathways for synergistic GH release. From there, explore related peptides through the See Also sections on each page to build a comprehensive understanding of the research landscape.
Russian Bioregulator Peptides
The complete Khavinson family of short peptides — organ-specific bioregulators that modulate gene expression in targeted tissues, developed at the St. Petersburg Institute of Bioregulation and Gerontology.
Oral Peptides
Peptides with demonstrated or researched oral bioavailability — including GLP-1 agonists, secretagogues, bioregulators, and emerging oral formulations.