Peptide Science & Learning

Cryo-EM structural determination of retatrutide bound to GLP-1R, GIPR, and GCGR in complex with heterotrimeric Gs proteins, mapping the N-terminal transmembrane recognition contacts underlying triple Class B1 GPCR agonism.

Ex-vivo pharmacological assay in isolated murine atrial preparations characterizing GCGR-, GIPR-, and GLP-1R-coupled adenylyl cyclase, intracellular cAMP, and protein kinase A (PKA) signalling pathways.

Pre-clinical murine assay examining renal pro-inflammatory cytokine (TNF-α, caspase-1, NLRP3) and pro-fibrotic marker (fibronectin, α-SMA, collagen I) gene expression alongside serum lipid and butyrate profiles.

Analytical validation of a C18 reversed-phase liquid chromatography–high-resolution mass spectrometry (LC-HRMS) method resolving single, dual, and triple receptor agonist peptides with sub-ppm mass accuracy and MS/MS fragment confirmation.

In-vitro receptor signalling and occupancy study demonstrating full GIPR agonism and biased GLP-1R signalling favouring cyclic AMP (cAMP) generation over β-arrestin recruitment and receptor internalisation.

Cryo-electron microscopy structure determination of tirzepatide bound to GIPR and GLP-1R, defining the near-atomic extracellular and transmembrane receptor-ligand interactions governing dual incretin agonism.

Cryo-EM and molecular dynamics analysis demonstrating how the C20 fatty-diacid acylation moiety and chimeric peptide sequence govern GIPR and GLP-1R receptor activation and reduced GLP-1R desensitisation.

Cellular and murine receptor-signalling study showing that long-acting GIPR agonism modulates intracellular insulin-receptor cascade cooperativity, glucose transport, glycerol conversion, and lipolytic flux in cultured adipocytes.

Ex-vivo rat Achilles tendon explant and cultured tendon fibroblast study demonstrating concentration-dependent acceleration of cellular migration, culture-dish spreading, H2O2 stress survival, and FAK–paxillin phosphorylation.

In-vitro human vascular endothelial cell and chick chorioallantoic membrane (CAM) study showing upregulated VEGFR2 mRNA/protein expression, receptor internalisation, and VEGFR2–Akt–eNOS phosphorylation.

cDNA microarray, RT-qPCR, and Western blot study in isolated rat Achilles tendon fibroblasts showing concentration- and time-dependent upregulation of growth hormone receptor expression and downstream JAK2 phosphorylation.

In-vitro human umbilical vein endothelial cell (HUVEC) transwell, scratch-migration, and Matrigel tube-formation assays demonstrating concentration-dependent cell-cycle progression and ERK1/2, FAK, and paxillin phosphorylation.

Biochemical study showing that the actin-sequestering peptide Fx and thymosin beta 4 are the same molecule, and describing how it binds actin monomers.

Review of the beta-thymosin peptide family: structure, distribution and known molecular interactions, including actin binding.

In-vitro endothelial cell adhesion, migration, tube-formation, and chick aortic-ring sprouting study demonstrating that the conserved central 7-amino-acid G-actin-binding motif (LKKTETQ) reproduces the angiogenic signalling of full-length thymosin β4.

Embryonic and postnatal cardiomyocyte culture and biochemical study showing that the G-actin-sequestering polypeptide thymosin β4 forms a functional PINCH–integrin-linked kinase (ILK) complex that activates protein kinase B (Akt) signalling.

Foundational biochemical and structure-function study demonstrating that the histidyl-lysyl tripeptide chelates copper(II) in equimolar coordination and facilitates cellular copper transport in cultured hepatoma cells.

In-vitro fibroblast culture study showing picomolar-to-nanomolar (10^-12 to 10^-9 M) stimulation of collagen biosynthesis by the GHK–Cu(II) coordination complex independent of cell-number changes.

Radiolabelled [3H]-glucosamine and [35S]-sulfate incorporation assay in cultured human fibroblasts demonstrating biphasic stimulation of extracellular dermatan sulfate and cell-layer heparan sulfate synthesis at 10^-9 to 10^-8 M GHK-Cu.

X-ray crystallographic structural study resolving the high-affinity square-pyramidal copper(II) coordination sphere formed by the N-terminal GHK tripeptide motif in recombinant fusion proteins.

Molecular and murine biochemical study demonstrating that nicotinamide phosphoribosyltransferase (NAMPT) and intracellular NAD+ levels oscillate under CLOCK:BMAL1 transcriptional control to regulate SIRT1 deacetylase activity.

Cellular and murine bioenergetics study showing that nuclear NAD+ depletion reduces SIRT1 activity and stabilises HIF-1α under normoxic conditions, downregulating mitochondrially encoded oxidative phosphorylation (OXPHOS) subunits.

Mechanistic review of subcellular NAD+ compartmentalisation, salvage-pathway enzymatic synthesis, sirtuin and PARP cosubstrate consumption, and the mitochondrial unfolded protein response (UPRmt).

Enzymatic and knockout-mouse study identifying the ectoenzyme NADase CD38 as a primary regulator of cellular NAD+ degradation, mitochondrial oxygen consumption, and SIRT3-dependent protein deacetylation.

Discovery study identifying a 16-amino-acid peptide encoded within a short open reading frame (sORF) of mitochondrial 12S rRNA that inhibits the folate-methionine cycle, accumulates endogenous AICAR, and activates AMPK in cultured cells.

Cell-biology and chromatin-binding study demonstrating AMPK-dependent nuclear translocation of MOTS-c under glucose restriction and direct interaction with ARE-regulated stress transcription factors including NRF2 (NFE2L2).

In-vitro human (LHCN-M2) and murine (C2C12) myoblast culture study showing that wild-type MOTS-c, via its conserved YIFY Src-homology-2 (SH2)-like motif, inhibits IL-6-induced STAT3 transcriptional activity and promotes myotube formation.

Cell-free biophysical and murine signalling study identifying casein kinase 2 (CK2) as a direct binding partner of MOTS-c and comparing wild-type vs K14Q variant peptide-protein interaction kinetics.

Structure-activity relationship study detailing the Aib8 substitution for DPP-4 enzymatic stability and Lys26 C18 fatty-diacid acylation with a γGlu-2xOEG linker for reversible serum albumin binding and high GLP-1R potency.

Molecular pharmacology review of acylated GLP-1 analogues examining fatty-acid linker chemistry, non-covalent albumin association, and intracellular GLP-1 receptor cAMP signalling cascades.

Liquid chromatography–high-resolution mass spectrometry (LC-HRMS) preformulation study mapping aqueous peptide bond hydrolysis, deamidation, and buffer-dependent stability profiles of semaglutide across pH and thermal conditions.

1.5-microsecond conventional molecular dynamics (cMD) and MM-GBSA free-energy simulation characterising non-covalent binding of the C18 diacid chain of semaglutide across fatty-acid binding pockets on serum albumin.

Medicinal chemistry design and structural optimisation of cagrilintide (AM833), detailing proline substitutions that prevent amyloid fibril formation alongside N-terminal C20 fatty-diacid lipidation for albumin binding.

In-vitro receptor pharmacology study profiling AM833 (cagrilintide) across canonical calcitonin receptor (CTR) and RAMP-complexed amylin receptors (AMY1R, AMY2R, AMY3R), quantifying cAMP, ERK1/2, and β-arrestin signalling.

Cryo-electron microscopy determination of calcitonin receptor–RAMP1/2/3 heterodimers bound to peptide agonists, elucidating how RAMP extracellular domains allosterically modulate amylin receptor peptide selectivity.

Small-angle X-ray scattering (SAXS), circular dichroism, and biophysical characterisation of fatty-acid-acylated amylin analogue self-association, oligomeric equilibrium, and physical stability in aqueous vehicles.

Two-dimensional 1H-NMR spectroscopy and distance-geometry structural determination of the biologically active 29-amino-acid N-terminal domain of growth hormone-releasing factor, identifying two α-helical regions.

In-vitro cell culture study demonstrating specific GHRH(1-29)-NH2 receptor binding, cellular proliferation, and vascular endothelial growth factor (VEGF) secretion in neuroendocrine cell lines.

Analytical review of synthetic GHRH(1-29) analogues including CJC-1295 and sermorelin, covering solid-phase sequence modifications, proteolytic cleavage pathways, and high-resolution mass spectrometry identification.

Validation of a nano-LC–quadrupole/Orbitrap high-resolution mass spectrometry workflow for separating and quantifying intact GHRH(1-29) analogues and their N-terminal enzymatic fragments.

Foundational receptor-pharmacology characterisation of the synthetic pentapeptide ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) in primary rat pituitary cells and in-vivo models, demonstrating high GHSR-1a selectivity without ACTH or cortisol elevation.

Medicinal chemistry and structure-activity relationship study of ipamorelin pentapeptide analogues evaluating N-methylated backbones and aromatic side-chain conformations in rat pituitary cell assays.

Pre-clinical rodent study quantifying concentration-dependent longitudinal bone growth rate and somatotroph hormone release following administration of the selective pentapeptide secretagogue ipamorelin.

Dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) study in rodent models examining cortical and cancellous bone mineral content under GHSR-1a agonist stimulation.

In-vitro telomerase-negative human fetal lung fibroblast (KMST-6) culture study demonstrating induction of hTERT catalytic subunit expression, telomerase enzymatic activity, and telomere length elongation.

Immunofluorescence, RT-qPCR, and molecular docking investigation showing that the Ala-Glu-Asp-Gly (AEDG) tetrapeptide binds histone H1/3/6/H4 complexes and upregulates Nestin, GAP43, β-tubulin III, and Doublecortin expression in cultured stem cells.

Comprehensive biochemical review of the synthetic tetrapeptide Ala-Glu-Asp-Gly (Epitalon), detailing its telomerase activation pathways, reactive oxygen species scavenging, and epigenetic chromatin interactions in cellular models.

Comparative in-vitro study across normal epithelial and immortalised cell lines quantifying hTERT mRNA expression, telomerase enzyme activity, and alternative lengthening of telomeres (ALT) promyelocytic leukaemia bodies.

Fluorescence spectroscopy and Oxygraph respirometry study demonstrating that the aromatic-cationic tetrapeptide SS-31 binds selectively to inner-mitochondrial-membrane cardiolipin with 1:1 stoichiometry, preventing cytochrome c peroxidase conversion and preserving ATP synthesis.

Biophysical and 31P/2H solid-state NMR study showing that SS-31 partitions into cardiolipin-rich anionic lipid bilayers to down-regulate membrane surface electrostatic potential and prevent divalent calcium-induced lipid packing stress.

High-resolution structural and biophysical analysis of sixteen SS-31 tetrapeptide variants evaluating aromatic side-chain composition, bilayer insertion depth, membrane surface charge modulation, and cellular ATP production.

Quantitative mass-spectrometry phosphoproteomics and mitochondrial respiration study in murine skeletal muscle mapping post-translational phosphorylation changes across electron-transport-chain and metabolic signalling proteins.

Foundational study designing the cell-permeable D-retro-inverso peptide FOXO4-DRI, demonstrating competitive disruption of nuclear FOXO4–p53 PML-body complexes, p53 nuclear exclusion, and selective caspase-3/7-mediated apoptosis in senescent cells.

In-vitro serial population-doubling culture study demonstrating that FOXO4-DRI selectively clears SA-β-gal-positive senescent chondrocytes and reduces senescence-associated secretory phenotype (SASP) marker expression.

NMR spectroscopy and isothermal titration calorimetry (ITC) study mapping the molecular binding interface between the FOXO4 forkhead-associated domain and the p53 transactivation domain.

High-resolution NMR, small-angle X-ray scattering (SAXS), and biochemical study demonstrating that FOXO4-DRI directly binds the intrinsically disordered p53 transactivation domain (TAD) with higher affinity than native FOXO4.

Two-dimensional 1H-NMR spectroscopy and molecular-mechanics conformational analysis of the α-MSH(11–13) C-terminal tripeptide Ac-Lys-Pro-Val-NH2 (KPV), defining its folded trans-proline secondary structure in solution.

In-vitro Caco-2, HT29-Cl.19A, and Jurkat T-cell study demonstrating that the oligopeptide transporter PepT1 mediates intracellular uptake of the KPV tripeptide to inhibit NF-κB and MAPK pro-inflammatory signalling cascades.

In-vitro bronchial epithelial cell study demonstrating that the tripeptide KPV suppresses TNF-α- and respiratory syncytial virus-induced NF-κB nuclear translocation and IL-8/eotaxin chemokine secretion.

Synthetic peptide chemistry and NMR spectroscopic characterisation of modified Lys-Pro-Val (KPV) tripeptide derivatives engineered to resist proteolytic aminopeptidase degradation in biological matrices.

PCR-array transcriptional profiling study in murine splenic cells demonstrating that the synthetic heptapeptide Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) and its Gly-Pro fragment modulate cytokine, chemokine, and receptor gene expression.

RT-qPCR gene-expression study in rat frontal cortex examining mRNA levels of 84 neurotransmission-related genes, demonstrating coordinated modulation of GABAA receptor subunits, transporters, and ion-channel transcripts by Selank.

In-vitro human neuroblastoma IMR-32 cell culture study demonstrating that Selank modulates GABAergic receptor subunit gene expression and acts as an allosteric modulator of GABAA receptor binding.

Biochemical and receptor-binding study characterising specific high-affinity membrane binding sites for radiolabelled [3H]-Selank and its allosteric modulation of [3H]-GABA binding on rat brain synaptosomal membranes.

Radioligand binding and immunoassay study using tritium-labelled [3H]-Semax on rat basal forebrain membranes, characterizing specific saturable receptor binding and concentration-dependent elevation of BDNF protein and mRNA in primary glial cultures.

RP-HPLC and uniformly tritium-labelled peptide degradation study elucidating the sequential aminopeptidase cleavage pathway of Semax (Met-Glu-His-Phe-Pro-Gly-Pro) into stable C-terminal hexapeptide and pentapeptide fragments.

Quantitative RT-PCR and immunohistochemistry study in rat hippocampal tissue demonstrating rapid upregulation of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) mRNA and protein levels.

Genome-wide RatRef-12 BeadChip microarray transcriptomic analysis mapping 96 immune-, chemokine-, immunoglobulin-, and vascular-signalling transcripts modulated by the heptapeptide Semax in rat cortical tissue.

1H-NMR spectroscopy and distance-restraint conformational study of the cyclic lactam melanocortin agonist scaffold Ac-Nle-cyclo[Asp-Pro-D-Phe-Arg-Trp-Lys] defining the spatial beta-turn orientation of the His/Pro-D-Phe-Arg-Trp pharmacophore.

Nuclear magnetic resonance (NMR) and 3D-QSAR pharmacophore modelling of cyclic lactam heptapeptides derived from the Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] scaffold, mapping steric and hydrophobic determinants of human MC4R selectivity.

Cryo-electron microscopy structure determination of the human melanocortin-4 receptor–Gs protein complex bound to cyclic peptide agonists including bremelanotide (PT-141), resolving calcium-cofactor coordination and transmembrane helix 6 activation.

In-vitro glioblastoma cell-culture assay investigating melanocortin receptor agonist bremelanotide (PT-141) effects on cellular proliferation, apoptosis markers, and intracellular survivin protein expression.

Fourier-transform infrared (FTIR), circular dichroism, and size-exclusion chromatography study examining how 0.9% w/v benzyl alcohol preservative interacts with polypeptide tertiary structures across solution pH and storage temperatures.

Size-exclusion chromatography, circular dichroism, differential scanning calorimetry, and dynamic light scattering evaluation of polypeptide stability in aqueous solutions containing bacteriostatic benzyl alcohol preservative.

High-sensitivity isothermal titration calorimetry (ITC), intrinsic tryptophan fluorescence, and dynamic light scattering study characterising polypeptide conformational equilibrium in 0.9% benzyl alcohol multi-use aqueous vehicles.

Hydrogen–deuterium exchange mass spectrometry (HDX-MS) analysis mapping local backbone amide exchange kinetics and polypeptide conformational stability in 0.9% benzyl alcohol aqueous buffer systems.

X-ray crystallography and biochemical enzymatic inhibition study characterising nicotinamide N-methyltransferase (NNMT) active-site recognition of S-adenosyl-L-methionine (SAM) and nicotinamide substrate pockets.

Structure-activity relationship, isothermal titration calorimetry, and crystal-structure analysis of small-molecule NNMT inhibitors targeting the nicotinamide and methyl-donor catalytic pocket.

Enzymatic kinetics, cellular 1-methylnicotinamide (1-MNA) quantification, and structural characterisation of selective small-molecule nicotinamide N-methyltransferase (NNMT) chemical probes.

Foundational neurochemical and cortical electroencephalography study of the synthetic nonapeptide Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu (DSIP) characterizing blood-brain barrier permeability and central delta-wave electrical activity.

Pre-clinical rodent chronobiology study comparing intact synthetic DSIP and its phosphorylated Ser7 analogue (DSIP-P) on circadian locomotor activity rhythms.

1H-NMR spectroscopy and molecular-mechanics conformational analysis determining the three-dimensional solution structure and intramolecular hydrogen-bonding network of cyclic DSIP nonapeptide analogues.

Neuroendocrine receptor-signalling study detailing how KISS1-derived C-terminal RF-amide peptides activate the G-protein-coupled receptor GPR54 (KISS1R) on hypothalamic GnRH neurons.

Molecular biology and receptor pharmacology review of the KISS1/GPR54 (KISS1R) signalling axis, mapping phospholipase C, intracellular calcium mobilisation, and ERK1/2 phosphorylation downstream of kisspeptin binding.

Site-specific furan-oxidation chemical cross-linking and mass-spectrometry study mapping direct ligand–receptor contact residues between the decapeptide Kisspeptin-10 (YNWNSFGLRF-NH2) and living GPR54-expressing cells.

Biochemical assay characterising the synthetic disulfide-cyclised C-terminal pentadecapeptide fragment hGH(177–191), demonstrating inhibition of acetyl-CoA carboxylase activity in isolated adipocytes and hepatocytes.

Pre-clinical rodent biochemical study examining ex-vivo adipose tissue lipolytic activity, lipogenic enzyme regulation, and absence of IGF-1 or glucose intolerance effects for synthetic C-terminal hGH(177–191) analogues.

Pre-clinical rodent study of the tyrosine-stabilised hexadecapeptide AOD-9604 (Tyr-hGH(177–191)), characterizing glycerol and free fatty acid release and hepatic pyruvate dehydrogenase activation without hGH receptor competition.

Chemical biology and transcriptomic study characterizing SLU-PP-332 as a selective synthetic pan-ERR (ERRα/β/γ) agonist that upregulates mitochondrial oxidative phosphorylation, FAO, and Ddit4/Slc25a25 transcriptional networks in C2C12 myocytes and murine skeletal muscle.

Pre-clinical murine study demonstrating that synthetic ERRα/β/γ activation by SLU-PP-332 increases cellular fatty acid oxidation and mitochondrial respiration rates in skeletal muscle and metabolic tissues.

Medicinal chemistry, molecular docking, and structure-activity relationship study of SLU-PP-332 acylhydrazone analogues mapping ligand-binding pocket interactions across estrogen-related receptors ERRα, ERRβ, and ERRγ.

Pharmacological profile of tesamorelin (TH9507), detailing N-terminal trans-3-hexenoyl conjugation to the 44-amino-acid human GHRH sequence to confer dipeptidyl peptidase-4 (DPP-4) resistance while preserving pituitary GHRH receptor affinity.

Biochemical and endocrine pharmacology review of trans-3-hexenoyl-GHRH(1–44)-NH2 examining pituitary somatotroph receptor activation, pulsatile GH secretion kinetics, and peripheral IGF-1 regulation.

Analytical chemistry and liquid chromatography–high-resolution mass spectrometry (LC-HRMS) review covering intact and metabolite detection of tesamorelin, sermorelin, and CJC-1295.

Analytical method development combining magnetic-bead immunoaffinity extraction with high-resolution quadrupole-Orbitrap tandem mass spectrometry (LC-HRMS/MS) to identify sermorelin (GHRH 1–29) and related GHRH analogues.

Comparative analytical chromatography and high-resolution mass spectrometry study optimising antibody-conjugated magnetic bead capture and extraction yield of sermorelin, tesamorelin, and CJC-1295.

In-vitro enzymatic and serum stability study mapping proteolytic cleavage kinetics and primary degradation fragments of sermorelin and related somatotropic peptides by LC-MS.

Pre-clinical murine and hepatocyte study demonstrating that dual GLP-1R/GCGR agonism by mazdutide downregulates PERK–eIF2α–ATF4 endoplasmic reticulum stress signalling and modulates hepatic lipid-oxidation gene networks.

Translational receptor-signalling review comparing balanced and biased GLP-1R/GCGR dual agonists including mazdutide and survodutide across cardiomyocyte, hepatic, and vascular adenylyl cyclase/cAMP pathways.

Mechanistic cellular and murine study demonstrating that tubular glucagon receptor (GCGR) activation by dual GLP-1R/GCGR agonists engages vacuolar H+-ATPase (V-ATPase) assembly and autophagic flux.

Receptor pharmacology and target-engagement profiling of survodutide (BI 456906), characterizing balanced sub-nanomolar GCGR and GLP-1R potency, C18 diacid albumin binding, and plasma amino-acid/glucagon pharmacodynamic biomarkers.

Fluorescence-labelled peptide biodistribution and whole-brain 3D light-sheet c-Fos imaging study in mice mapping survodutide binding across circumventricular organs (area postrema, median eminence) and parabrachial nuclei.

Comparative mechanistic analysis of dual GCGR/GLP-1R receptor agonists examining receptor-binding stoichiometry, intracellular cAMP generation, and systemic metabolic pathway modulation.

Biochemical review of intracellular γ-L-glutamyl-L-cysteinyl-glycine (GSH) biosynthesis via glutamate-cysteine ligase (GCL) and glutathione synthetase, detailing protein S-glutathionylation and Nrf2 redox signalling.

Molecular enzymology study of the two-step ATP-dependent synthesis of reduced glutathione (GSH), transcriptional regulation of GCLC/GCLM subunits, and thiol-disulfide (GSH/GSSG) redox buffering.

Cellular biochemistry study examining glutathione transport across peroxisomal membranes, glutathione peroxidase/reductase cycles, and hydrogen peroxide detoxification in mammalian organelles.

Biochemical and neurochemical assay demonstrating that synthetic oligopeptides mimicking the N-terminal α-helical domain of SNAP-25 competitively inhibit ternary SNARE complex assembly and calcium-dependent vesicular exocytosis.

Structural and biochemical investigation showing how the N-terminal peptide region of SNAP-25 interacts with vesicular effectors to regulate syntaxin-1A/VAMP2 four-helix bundle SNARE complex formation.

Biophysical and fluorescence spectroscopy study characterizing the conformational dynamics of unstructured SNAP-25 domains and their assembly into ternary SNARE complexes.