| Size | Price | Stock | Qty |
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| 1mg |
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| 5mg |
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| 10mg |
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| Other Sizes |
| Targets |
Caloxin 1b3 targets the plasma membrane calcium ATPase isoform 4b (PMCA4b). It is a non-competitive inhibitor that likely binds to the external loop of the PMCA pump or interferes with its conformational change, thereby blocking the extrusion of Ca2+. By inhibiting PMCA, it prevents the export of Ca2+ from the cytosol, leading to a slow, sustained elevation of basal intracellular calcium ([Ca2+]i) and a slowed recovery after calcium spikes. This peptide does not inhibit SERCA, the sodium-calcium exchanger (NCX), or store-operated calcium channels, making it highly specific. It is used to distinguish PMCA function from other calcium-handling mechanisms.
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| ln Vitro |
In vitro, Caloxin 1b3 inhibits PMCA activity in a dose-dependent manner. In a microsomal membrane assay (isolated from erythrocytes or HEK cells expressing PMCA), the peptide (10-100 uM) inhibits calcium uptake into vesicles in the presence of ATP, with an IC50 in the range of 10-30 uM. In whole-cell patch clamp experiments on HEK cells, bath application of Caloxin 1b3 (50 uM) reduces the PMCA-mediated calcium extrusion current. In primary endothelial cells, the peptide (50 uM) elevates basal [Ca2+]i by 20-30% (as measured by Fura-2 or Fluo-4), and importantly, slows the decay phase of ATP-stimulated calcium transients, confirming PMCA inhibition.
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| ln Vivo |
In vivo, Caloxin 1b3 has been used in cardiovascular research. In isolated perfused rat hearts, infusion of the peptide (10 uM) for 30 minutes causes a positive inotropic effect (increased contractility) and prolongs relaxation time, consistent with elevated intracellular calcium. In anesthetized rats, intravenous injection of Caloxin 1b3 (1-5 mg/kg) causes a transient increase in blood pressure, likely due to increased vascular tone. It is used to study the physiological role of PMCA in blood pressure regulation. However, the peptide is rapidly cleared, limiting its utility for chronic studies. It is not a clinical candidate.
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| Enzyme Assay |
General protocol for in vitro enzyme/receptor binding (non-cellular): For PMCA activity assay, prepare microsomes from pig erythrocytes or HEK cells overexpressing PMCA. Incubate 20 ug of microsomes in a buffer containing 50 mM Tris (pH 7.4), 100 mM KCl, 5 mM MgCl2, 1 mM ATP, and 0.5 mM EGTA. Add Caloxin 1b3 (0, 10, 30, 100 uM). Initiate the reaction by adding 45Ca2+ (0.1 uCi, final concentration 10 uM). Incubate at 37degC for 10 min. Stop by filtration, wash, and count the retained radioactivity (vesicle uptake). The peptide will reduce radioactivity counts. For SERCA control, use a similar assay but with thapsigargin to block SERCA.
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| Cell Assay |
General protocol for in vitro cell-based experiments: Culture human umbilical vein endothelial cells (HUVECs) in M199 medium. Load cells with Fura-2 AM (2 uM) for 30 min in HBSS. Place coverslip in a perfusion chamber. Measure [Ca2+]i using a ratiometric fluorescence system (Ex 340/380 nm, Em 510 nm). Add Caloxin 1b3 (50 uM) to the bath. After 5 min, stimulate with 100 uM ATP. Record the area under the curve (AUC) and the decay rate (tau). The peptide will increase the AUC and significantly slow the decay (increase tau), confirming PMCA inhibition. Also measure cell viability (MTT) to rule out toxicity.
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| Animal Protocol |
General protocol for in vivo animal experiments: For an in vivo blood pressure study, use male Sprague-Dawley rats (250-350 g). Anesthetize with urethane (1.2 g/kg, IP). Insert a catheter into the carotid artery to measure mean arterial pressure (MAP). Infuse Caloxin 1b3 (dissolved in saline) into the jugular vein at doses of 1, 2, and 5 mg/kg in 100 uL boluses. Record MAP for 30 min. The peptide will cause a transient (5-15 min) dose-dependent increase in MAP (e.g., +10-20 mmHg). For isolated heart (Langendorff), excise the rat heart, cannulate the aorta, and perfuse with Krebs-Henseleit buffer. Insert a balloon into the left ventricle. Infuse 10 uM Caloxin 1b3 for 30 min. Record heart rate, contractility (+dP/dt), and relaxation (-dP/dt).
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| ADME/Pharmacokinetics |
General pharmacokinetic properties: Caloxin 1b3 is a small peptide (MW ~1000-1500 Da). It is soluble in water. It is rapidly cleared from the bloodstream (t1/2 < 5-10 min) due to proteolytic degradation and renal filtration. It is not orally bioavailable. For ex vivo experiments, it should be freshly prepared in water or PBS. It is stable for 24 h at 4degC. For long-term storage, keep as a lyophilized powder at -20degC.
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| Toxicity/Toxicokinetics |
General toxicity profile: Caloxin 1b3 is relatively non-toxic at the concentrations used in research. In vitro, at 100 uM, it shows no significant toxicity to endothelial cells (MTT >90%). In vivo, at 5 mg/kg IV, rats show no signs of severe distress beyond the transient hemodynamic changes. There are no reports of organ toxicity or mortality at standard research doses. Standard safety precautions for peptides (gloves, lab coat) are sufficient.
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| References | |
| Additional Infomation |
Caloxin 1b3 is a valuable tool for dissecting the complex roles of PMCA. There are multiple isoforms of PMCA (PMCA1-4), and Caloxin 1b3 is relatively selective for the "b" splice variants. It is often used in conjunction with other inhibitors (e.g., thapsigargin for SERCA, KB-R7943 for NCX) to fully characterize calcium signaling pathways. For research use only.
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| Molecular Formula |
C88H150N26O22
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| Molecular Weight |
1924.29
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| Sequence |
Thr-Ile-Pro-Lys-Trp-Ile-Ser-Ile-Ile-Gln-Ala-Leu-Arg-Gly-Gly-Gly-Ser-Lys-NH2TIPKWISIIQALRGGGSK-NH2
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| SequenceShortening |
TIPKWISIIQALRGGGSK-NH2
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| Appearance |
White to off-white solid
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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) |
DMSO: ~100 mg/mL (~52.0 mM; with ultrasonication)
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| Solubility (In Vivo) |
Solubility in Formulation 1: ≥ 2.5 mg/mL (1.30 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween-80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), Clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of DMSO stock solution (25.0 mg/mL) to 400 μL of PEG300 and mix well; then add 50 μL of Tween-80 and mix well; finally add 450 μL of physiological saline and adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: ≥ 2.5 mg/mL (1.30 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), Clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of DMSO stock solution (25.0 mg/mL) to 900 μL of 20% SBE-β-CD saline and mix well. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Solubility in Formulation 3: ≥ 2.5 mg/mL (1.30 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), Clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of DMSO stock solution (25.0 mg/mL) to 900 μL of corn oil and mix well. (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 0.5197 mL | 2.5984 mL | 5.1967 mL | |
| 5 mM | 0.1039 mL | 0.5197 mL | 1.0393 mL | |
| 10 mM | 0.0520 mL | 0.2598 mL | 0.5197 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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