| Size | Price | Stock | Qty |
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| 5mg |
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| 50mg |
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| Targets |
YKYY TFA targets the transferrin receptor (TfR, also known as CD71), a transmembrane glycoprotein that mediates cellular uptake of iron-bound transferrin via clathrin-dependent endocytosis. TfR is highly expressed on the luminal side of brain capillary endothelial cells, making it a well-established target for receptor-mediated transcytosis across the blood-brain barrier (BBB). YKYY binds to TfR with moderate affinity (KD in the low micromolar range) and can be used as a targeting ligand. Upon binding, the peptide-receptor complex is internalized and then transcytosed to the abluminal side, allowing delivery of conjugated cargo into the brain. The peptide does not activate signaling pathways; its role is purely as a carrier.
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| ln Vitro |
In vitro, YKYY peptide binds to transferrin receptor-expressing cells. A typical binding assay: culture human brain microvascular endothelial cells (hCMEC/D3) or TfR-overexpressing CHO cells in appropriate medium. Treat cells with fluorescently labeled YKYY (e.g., FITC-YKYY, 1-100 uM) for 30-60 min at 37degC. Measure uptake by flow cytometry or fluorescence microscopy. Competition with excess free YKYY or anti-TfR antibody reduces uptake. The peptide does not inhibit cell viability up to 100 uM. For transcytosis studies, use an in vitro BBB model (co-culture of hCMEC/D3 or primary brain endothelial cells with astrocytes). Add YKYY-conjugated nanoparticles or liposomes to the apical chamber, measure basolateral fluorescence after 2-4 h. YKYY enhances transcytosis compared to untargeted controls. No cytotoxicity. DMSO not used (water-soluble).
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| ln Vivo |
In vivo, YKYY-conjugated nanoparticles or liposomes show enhanced brain accumulation after intravenous administration. In a typical study, male BALB/c or C57BL/6 mice (6-8 weeks) are injected via tail vein with fluorescently labeled YKYY-targeted nanoparticles (e.g., PEG-PLA or liposomes) at 5-20 mg/kg (lipid dose). Free YKYY peptide (unconjugated) is not administered alone for efficacy; it is only used as a targeting ligand. At 1-24 h post-injection, mice are perfused to remove intravascular signal, brains are harvested, and fluorescence is measured (IVIS imaging or homogenization). YKYY-targeted nanoparticles show 2-5 fold higher brain uptake compared to non-targeted controls. The peptide enhances BBB penetration via TfR-mediated transcytosis. For research use only.
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| Enzyme Assay |
For non-cellular TfR binding assay, immobilize recombinant human transferrin receptor (TfR) protein on a CM5 sensor chip by amine coupling. Dilute YKYY peptide in running buffer (10 mM HEPES pH 7.4, 150 mM NaCl, 0.005% Tween 20). Inject increasing concentrations of YKYY (1-1000 uM) at 30 uL/min for 60 s, dissociation 120 s. Regenerate with 10 mM glycine-HCl pH 2.0. Calculate KD. Alternatively, biotinylate YKYY and use a streptavidin-based capture assay. No enzyme inhibition assays are performed. This is the primary biochemical characterization.
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| Cell Assay |
For in vitro cell binding and uptake assays, culture human brain microvascular endothelial cells (hCMEC/D3) in EBM-2 medium with 5% FBS, 1% P/S, and supplements at 37degC, 5% CO2. Seed cells in 96-well plates (2×10⁴ cells/well) for fluorescence measurement, or in 24-well plates (1×10⁵ cells/well) for flow cytometry. Synthesize FITC-labeled YKYY (FITC-betaAla-YKYY) or conjugate YKYY to fluorescent nanocarriers. For binding, add FITC-YKYY (1-100 uM) in serum-free medium, incubate at 4degC for 1 h (to prevent internalization). Wash 3× with cold PBS, lyse cells with 1% Triton X-100, and measure fluorescence (Ex 485/Em 528). For internalization, incubate at 37degC for 30-60 min, then wash, trypsinize (to remove surface-bound peptide), and analyze by flow cytometry. Competition: pre-incubate with 10-fold excess unlabeled YKYY or with anti-TfR antibody (e.g., OKT9, 10 ug/mL). Positive control: transferrin (holo-Tf, 10 ug/mL). Negative control: scrambled peptide (e.g., YKYY scrambled). DMSO not used. All experiments in triplicate.
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| Animal Protocol |
For in vivo brain targeting, use female BALB/c nude mice or C57BL/6 mice (6-8 weeks, 18-22 g, n=5/group). Prepare YKYY-conjugated liposomes: e.g., DSPC:Cholesterol:DSPE-PEG2000-YKYY (molar ratio 50:45:5) by thin-film hydration. Include a fluorescent dye (e.g., DiR, Cy5.5) for imaging. For non-targeted control, use liposomes without YKYY or with PEG2000 only. Administer intravenously via tail vein at a dose of 10 mg/kg (lipid concentration). At 1, 4, 8, 24 h post-injection, perfuse mice with PBS to remove intravascular dye, then harvest brains and major organs (liver, spleen, kidney, lung). For ex vivo imaging, use IVIS Spectrum (Ex 710/Em 760 for DiR). For quantification, homogenize tissues and extract dye with organic solvent, measure fluorescence. YKYY-targeted liposomes show significantly higher brain fluorescence and lower liver/spleen uptake than non-targeted liposomes. For histological analysis, perfuse with 4% paraformaldehyde, freeze brains, cut sections, and image fluorescence. For research use only.
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| ADME/Pharmacokinetics |
YKYY peptide is a small tetrapeptide (MW ~ 650 for free base). When conjugated to nanoparticles, its pharmacokinetics are dictated by the carrier. Free YKYY peptide alone, if administered IV, would have a very short half-life (minutes) due to rapid proteolysis and renal clearance. It is not intended for use alone. For storage, lyophilized powder at -20degC for up to 3 years; in DMSO or water at -80degC for 6 months. Solubility: water, DMSO. Protect from moisture.
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| Toxicity/Toxicokinetics |
No toxicity data for YKYY alone. At concentrations used in vitro (up to 100 uM), no cytotoxicity in endothelial cells. In vivo, YKYY-conjugated nanoparticles are generally well-tolerated at single-dose studies. Standard peptide handling: use PPE. For research only.
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| References | |
| Additional Infomation |
Sequence: Tyr-Lys-Tyr-Tyr (YKYY). Molecular weight: 649.69 (free base). Purity >95% by HPLC. TFA salt. Targets transferrin receptor (TfR). Used for brain drug delivery research. Not for human use.
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| Molecular Formula |
C35H42F3N5O10
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| Molecular Weight |
749.73
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| Related CAS # |
YKYY
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| Sequence |
Tyr-Lys-Tyr-TyrYKYY
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| Appearance |
Solid powder
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| HS Tariff Code |
2934.99.9001
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| Storage |
Powder -20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month Note: Please store this product in a sealed and protected environment, avoid exposure to moisture. |
| Shipping Condition |
Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)
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| Solubility (In Vitro) |
May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples
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| Solubility (In Vivo) |
Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.
Injection Formulations
Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)(e.g. IP/IV/IM/SC) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). View More
Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] Oral Formulations
Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). View More
Oral Formulation 3: Dissolved in PEG400 (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 1.3338 mL | 6.6691 mL | 13.3381 mL | |
| 5 mM | 0.2668 mL | 1.3338 mL | 2.6676 mL | |
| 10 mM | 0.1334 mL | 0.6669 mL | 1.3338 mL |
*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.
Calculation results
Working concentration： mg/mL；
Method for preparing DMSO stock solution： mg drug pre-dissolved in μL DMSO (stock solution concentration mg/mL). Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug.
Method for preparing in vivo formulation:：Take μL DMSO stock solution, next add μL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O，mix and clarify.
(1) Please be sure that the solution is clear before the addition of next solvent. Dissolution methods like vortex, ultrasound or warming and heat may be used to aid dissolving.
(2) Be sure to add the solvent(s) in order.
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