| Size | Price | Stock | Qty |
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| 1mg |
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| 5mg |
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| Other Sizes |
| Targets |
JF646 Maleimide does not target a specific biological receptor or enzyme; its reactive maleimide group targets free thiol groups (-SH) on cysteine side chains. The dye itself is a fluorophore used for visualizing labeled biomolecules. The maleimide reacts specifically with reduced thiols at pH 6.5-7.5 to form stable thioether bonds, enabling site-specific labeling of proteins.
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| ln Vitro |
λmax(nm)=646; λem(nm)=664[1]. JF646, Maleimide undergoes modification. Red fluorescent dye JF646 has a high extinction coefficient, is photostable, and is membrane-permeable[2].
JF646 Maleimide is not used in enzyme/receptor binding assays but rather as a labeling agent. Its spectral properties (absorption max ~646 nm, emission max ~664 nm) are measured in cell-free buffer solutions. The dye exhibits high quantum yield (typically >0.3) and excellent photostability, making it suitable for single-molecule localization microscopy (SMLM) and stimulated emission depletion (STED) microscopy. |
| ln Vivo |
In cell-free systems, JF646 Maleimide is incubated with purified proteins containing engineered cysteine residues. The labeling efficiency and specificity are analyzed by SDS-PAGE and in-gel fluorescence scanning. The maleimide reacts preferentially with reduced thiols; excess reagent is quenched with beta-mercaptoethanol or DTT. The labeled protein retains its functional activity if the cysteine is not essential.
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| Enzyme Assay |
For thiol labeling, a purified protein (10-100 uM) is reduced with TCEP (1-5 mM) for 30 minutes at room temperature to ensure free thiols. The reducing agent is removed by buffer exchange. JF646 Maleimide (3-10 molar excess) is added and incubated at room temperature for 1-2 hours or at 4degC overnight. The reaction is stopped with excess beta-mercaptoethanol. Unbound dye is removed by desalting or dialysis. Labeling efficiency is confirmed by mass spectrometry.
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| Cell Assay |
Live or fixed cells expressing a target protein with a cysteine tag (or via antibody labeling) are incubated with JF646 Maleimide. For surface thiol labeling, cells are treated with the dye (1-10 uM) in PBS for 15-30 minutes at 4degC, then washed. For intracellular labeling, cells are first fixed and permeabilized. Labeled cells are imaged by confocal or super-resolution microscopy. Specificity is controlled by pre-blocking thiols with N-ethylmaleimide.
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| Animal Protocol |
JF646 Maleimide is used in vivo for imaging studies, typically conjugated to a targeting moiety (e.g., antibody, peptide). The conjugate is administered intravenously in mice (0.1-5 mg/kg). Imaging is performed using near-infrared fluorescence imaging systems at 640 nm excitation. The dye exhibits low background and good tissue penetration. Biodistribution can be assessed by ex vivo organ imaging after 1-24 hours.
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| ADME/Pharmacokinetics |
As a small-molecule dye (MW ~800-1000 Da), JF646 Maleimide itself has rapid clearance and non-specific distribution. When conjugated to a targeting vector, the PK properties are governed by the conjugate. The dye has high aqueous solubility and photostability. It is stable in serum for several hours. The maleimide group is hydrolyzed slowly at pH >8; storage at -20degC under inert atmosphere is recommended.
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| Toxicity/Toxicokinetics |
JF646 Maleimide is non-toxic at typical labeling concentrations (≤10 uM). In animal studies using conjugates, no significant toxicity has been reported. The dye does not interfere with cell viability or normal physiology. Standard safety precautions (gloves, lab coat) should be followed. The compound is not intended for human use; no clinical toxicity data are available.
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| References |
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| Additional Infomation |
JF646 Maleimide is a research-use-only fluorescent probe developed by the Janelia Research Campus. It is not approved for diagnostic or therapeutic use. The dye is part of the Janelia Fluor® family known for high brightness and photostability. The maleimide derivative enables site-specific labeling of thiols in vitro and in live cells. It is compatible with various microscopy techniques including STED, PALM, and confocal imaging.
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| Molecular Formula |
C35H34N4O5SI
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| Molecular Weight |
618.75
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| Related CAS # |
Janelia Fluor® 646, SE;1811539-59-9;Janelia Fluor® 646, Azide;Janelia Fluor® 646 TFA
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| Appearance |
Light green to green 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: This product requires protection from light (avoid light exposure) during transportation and storage. |
| 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 | 1.6162 mL | 8.0808 mL | 16.1616 mL | |
| 5 mM | 0.3232 mL | 1.6162 mL | 3.2323 mL | |
| 10 mM | 0.1616 mL | 0.8081 mL | 1.6162 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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