Stress-recovery research peptide (modified CRF fragment)
A lab-made tweak of the brain's stress-signal hormone, redesigned to switch on the body's 'calm-down after stress' receptor instead of the alarm one. Used only as a research tool, not a medicine.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Corticotropin-releasing factor [1-40; E26, I40] is a synthetic, 40-residue analog of human CRF — the hypothalamic hormone that launches the body's stress response. The bracketed notation marks two amino acid substitutions from the native CRF sequence: a glutamate (E) at position 26 and an isoleucine (I) at position 40. These changes shift receptor preference toward CRHR2, the second of two CRF receptors, which is thought to counterbalance the acute stress-response drive of CRHR1. The peptide is primarily a laboratory research tool used to selectively probe CRHR2 biology. Patthy and colleagues (1986) isolated a family of CRF-related polypeptides from porcine hypothalami — including peptides sharing this sequence — and confirmed their ability to stimulate corticotropin release from rat pituitary cells, establishing the structural lineage from which designed CRHR2-selective analogs like this one descend.
What it does
In the body, CRF acts as the upstream trigger for the stress axis: the hypothalamus releases CRF, which reaches the pituitary and prompts secretion of ACTH, which in turn drives cortisol release from the adrenal glands. The two CRF receptors — CRHR1 and CRHR2 — do not play identical roles. CRHR1 is broadly linked to acute stress arousal and anxiety-like behavior, while CRHR2 is associated with physiological recovery, stress adaptation, and cardiac function. Because this analog selects preferentially for CRHR2, researchers use it to study those downstream CRHR2-mediated effects in isolation — without the confounding activity at CRHR1 that the native CRF sequence would produce.
Evidence
- Human: No human trials reported for this analog. It is an investigational research compound.
- Animal: The CRF peptide family from which this analog derives was characterized in porcine hypothalami and validated for CRF activity in rat pituitary superfusion experiments (Patthy and colleagues, 1986).
- In vitro: CRHR2 binding and functional selectivity profiling are the primary experimental uses; specific binding values for this variant are not reported in the sources available here.
Mechanism
Corticotropin-releasing factor receptors (CRHR1 and CRHR2) are class B G protein-coupled receptors that signal primarily through Gs, raising intracellular cAMP and activating downstream kinase cascades. Wild-type CRF binds both receptors, but the two positions altered in this analog — 26 and 40 — influence receptor contact geometry in ways that favor CRHR2 engagement. CRHR2 is expressed in peripheral tissues including the heart, skeletal muscle, and gastrointestinal tract, as well as in select brain regions, giving it a profile more associated with peripheral physiology and stress recovery than the CNS stress-alarm role associated with CRHR1. This analog is therefore used as a pharmacological probe to dissect CRHR2-specific signaling in experimental systems where receptor subtype selectivity is required for a clean interpretation.
Open questions
- No binding affinity data (Ki or IC50 at CRHR1 vs. CRHR2) are available in public sources for this specific variant; rigorous selectivity quantification remains to be published.
- Functional consequences of CRHR2 engagement — anxiolysis, cardioprotective effects, energy homeostasis — have been studied with native CRHR2-preferring ligands (urocortins 2 and 3) but direct comparison of this synthetic analog against those ligands in the same assay system has not been described in the available literature.
- The role of the I40 substitution in particular in determining receptor selectivity versus simple C-terminal stability is not resolved in the published literature accessible here.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Would restoring the missing chemical modification at the end of this peptide boost its binding to the recovery receptor without losing its ability to ignore the anxiety receptor?
If so, chemists have a simple one-step improvement to convert this research compound into a high-quality therapeutic candidate for stress, cardiac, and metabolic conditions, saving significant time and cost compared to designing a new peptide from scratch.
Does adding a negative electrical charge at position 26 of this stress peptide push it away from the anxiety-driving receptor and toward the calming one?
If charge at position 26 is the key, chemists could design new stress-hormone drugs with precise receptor targeting by adding or removing charges at this position, leading to more specific treatments for stress disorders with fewer off-target effects.
Does this modified CRF peptide attach to the recovery receptor without fully activating it, producing only a partial signal?
Partial activators can sometimes be better drugs than full activators because they produce a controlled, moderate response. If confirmed, this peptide could serve as a template for safer stress-recovery drugs that avoid the risks of over-stimulating the CRHR2 system in the heart and brain.
Can this modified stress hormone reduce food intake by activating hunger-control circuits in the brain without triggering the anxiety effects of the stress hormone system?
If this peptide suppresses appetite via CRHR2 without anxiety side effects, it could serve as a model for a new class of weight-control drugs that tap into the brain's stress-recovery system rather than the anxiety-driving stress system, potentially offering a safer path to treating obesity.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.7991151213645935 | openfold3-mlx |
| ranking score | 0.8691758513450623 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.717 | global PDE — lower = better |
| disorder | 0.171 | fraction disordered |
| chain pair ipTM (A, B) | 0.799 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | aedd8f3eb814e392… |
| hardware | apple_m4_base_16gb |
| mlx version | 0.31.1 |
| python | 3.14.3 |
| random seed | 42 |
| msa strategy | colabfold |
| diffusion samples | 1 |
| runtime | 349s |
| predicted by | mlx@peptide |
| predicted at | 2026-04-22 |
python3 openfold3/run_openfold.py predict --query_json {query.json} --runner_yaml examples/example_runner_yamls/mlx_runner.yml --output_dir {output_dir} --num_diffusion_samples 1 ▸citationbibtex
@peptide{pep10647,
sequence = {SEEPPISLDLTFHLLREVLEMARAEELAQQAHSNRKLMEI},
target = {crhr2},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}