azido-peg3-maleimide (bp-22468)
product name: azido-peg3-maleimide
catalog number: bp-22468
chemical structure:
formular: c15h23n5o6
molecular weight: 369.4
solubility: dmso, dmf, dcm
appearance: vial 1 off-white to grey solid; vial 2 slightly yellow oil
storage: upon receipt store at -20°c. product shipped at ambient temperature
shelf life: for each component, at least 12 months at -20oc
important note: azido-peg3-maleimide degrades quickly (hours) at room temperature. this product is provided as a two-component kit. the stock solution of azido-peg3-maleimide is prepared in situ.
introduction
azido-peg3-maleimide is mainly used to crosslink two biomolecules together. the maleimide reacts with thiolcontaining compound at ph 6.5 to 7.0 to activate the molecules, then the azide will react with alkyne-containingcompound to yield the conjugates.
note:
• ph for the thiol-maleimide reaction: 6.5-7.5.the maleimide group reacts predominantly with free sulfhydryls to form thioether. at ph > 7.0, primary amines willalso react with maleimide, and hydrolysis of the maleimide groups will occur. at ph 7, the maleimide group is ~1,000times more reactive toward a free sulfhydryl than to an amine.
• thiol and azide free: no thiol and azide residual in biomolecules and buffers.
additional materials required
• co-solvent: dimethyl sulfoxide (dmso) or dimethyl formamide (dmf)
• reducing reagents: tcept or immobilized tcep disulfide reducing gel
• reaction buffer: pbs buffer (ph 6.5‐7.0) with 5‐10 mm edta
• (optional) quenching buffer: concentrated (0.5‐1 m) cysteine, ddt or other thiol containing reducingagents
• spin desalting columns
1. add 2.5ml of dry dmf or dmso to azido‐peg3‐amine (vial #2) and shake for ~30 seconds.
2. add the solution above slowly to maleimide‐nhs ester (vial #1, white solid) under a dry n2 atmosphereslowly, stir for 30 minutes at room temperature. the progress of the reaction can be followed by tlc.
3. stock solution of azido‐peg3‐maleimide is ready to use. at this stage the product is stable if storedat ‐20c or lower for short periods of time (hours).
4. the concentration of azide‐peg3‐maleimide stock solution is about 120 mm, i.e. is amount: 0.3 mmol.
5. tlc data: methanol: methylene chloride 1:20 or 4 ml: 10 drops, silica gel normal phase plate developedwith a potassium permanganate spray.
e.g. the rf of the azido‐peg3‐maleimide is slightly lower one of the maleimide‐nhs ester. when thereaction is complete, it will be one clean spot on the plate.
procedure for labeling proteins
1. if required, buffer exchange the protein sample into pbs at 1‐5 mg/ml by using a spin desalting column.
2. add tcep stock solution to the protein solution at final concentration of 20 mm, pipette up anddown several times to mix.
3. incubate the reaction for 30 minutes.
4. buffer exchange into reaction buffer to remove excess tcep.note: edta need be added to reaction buffer to a final 5‐10 mm to avoid s-s bind reformation.
5. add a 20 x freshly prepared maleimide reagent above to the protein sample.
6. incubate reaction mixture for 1‐4 hour at room temperature or for 2‐8 hours at 4°c.note: many proteins will precipitate when the dmf or dmso concentration exceeds 10% of the final reaction volume.
7. remove the excess reagent by desalting the labeled protein through a spin desalting column or bydialysis.
procedure for click reaction
please check a corresponding protocol in the peg linkers for click chemistry for details.