Azido-PEG20-alcohol: Handling, Storage & Application Guide

Azido-PEG20-alcohol is a heterobifunctional polyethylene glycol reagent bearing a terminal azide group and a hydroxyl group, designed to introduce azide functionality via copper-catalyzed or strain-promoted click chemistry while providing a hydrophilic PEG20 spacer for improved solubility and reduced nonspecific binding.

SKU

A596194

Functional Groups

Terminal azide (–N₃) and hydroxyl (–OH)

PEG Chain Length

20 ethylene oxide units

Primary Application

CuAAC and SPAAC click chemistry bioconjugation

Solubility

Soluble in water and common organic solvents (e.g., DMSO, DMF)

Storage Condition

–20 °C, protected from light and moisture; minimize freeze-thaw cycles

Product Overview and Chemical Properties

Azido-PEG20-alcohol (SKU: A596194) is a heterobifunctional PEG reagent with a discrete 20-unit polyethylene glycol chain flanked by an azide (–N₃) group at one terminus and a hydroxyl (–OH) group at the other. The azide moiety participates selectively in copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) or strain-promoted azide–alkyne cycloaddition (SPAAC) reactions, enabling highly specific, bioorthogonal ligation without interference from native biological functional groups. The hydroxyl terminus can be further derivatized using standard esterification, etherification, or carbamate-forming reactions, providing a versatile handle for downstream chemistry.

The 20-unit PEG spacer confers exceptional aqueous solubility, reduces aggregation of conjugated molecules, and minimizes nonspecific adsorption to proteins and surfaces. These properties make Azido-PEG20-alcohol particularly valuable in applications where steric accessibility and low background binding are critical, such as the preparation of antibody–drug conjugates, PEGylated nanoparticles, and surface-functionalized biosensors.

Storage and Handling Guidelines

Storage: Store Azido-PEG20-alcohol at –20 °C in a tightly sealed container, protected from light and atmospheric moisture. Prolonged exposure to heat, light, or humidity can lead to hydrolysis of the PEG chain or decomposition of the azide group, reducing reagent efficacy. Minimize the number of freeze-thaw cycles by preparing single-use aliquots upon first thaw.

Reconstitution: Allow the vial to equilibrate to room temperature before opening to prevent condensation-induced hydrolysis. For stock solutions, dissolve in anhydrous DMSO or DMF at a concentration appropriate for your assay (typically 10–100 mM), then dilute into aqueous buffer as needed. Aqueous stock solutions should be prepared fresh or stored at –80 °C if short-term storage is required.

Safety: Organic azide compounds can be potentially explosive in bulk quantities or under strong heating. Handle with standard laboratory precautions; avoid contact with flames, strong acids, or reducing agents that could decompose the azide. Wear appropriate personal protective equipment (gloves, eye protection, lab coat). Dispose of azide-containing waste according to institutional and local regulations.

Recommended Protocols for Click Chemistry Conjugation

CuAAC Protocol (copper-catalyzed):

1. Prepare a 10 mM stock of Azido-PEG20-alcohol in anhydrous DMSO. Dilute to the desired working concentration (typically 0.1–1 mM) in phosphate-buffered saline (PBS, pH 7.2–7.4) or another compatible aqueous buffer.
2. Mix the azido compound with the alkyne-bearing partner molecule at a 1:1 to 1.5:1 molar ratio (azide:alkyne).
3. Add CuSO₄ (1 mM final concentration) and sodium ascorbate (5 mM final concentration) to generate Cu(I) in situ. Optionally include a Cu-stabilizing ligand such as THPTA or BTTAA (5–10 mM) to improve reaction efficiency and reduce copper-mediated oxidative damage to sensitive biomolecules.
4. React at room temperature for 1–4 hours with gentle agitation, under inert atmosphere if possible.
5. Purify the conjugate by dialysis, size-exclusion chromatography, or HPLC to remove copper catalyst and unreacted reagents.

SPAAC Protocol (copper-free, strain-promoted):

1. Dissolve Azido-PEG20-alcohol to working concentration in PBS or cell-culture-compatible buffer.
2. Mix with a cyclooctyne-functionalized partner (e.g., DBCO- or BCN-labeled molecule) at a 1:1 to 2:1 molar ratio (azide:cyclooctyne).
3. React at room temperature for 1–16 hours (reaction time depends on the cyclooctyne reagent's second-order rate constant and concentration).
4. Purify as above. SPAAC is preferred for live-cell labeling or copper-sensitive applications.

Applications

Azido-PEG20-alcohol is suitable for a broad range of research and development applications:

• Antibody–Drug Conjugates (ADCs): The hydroxyl group can be converted to an active ester or carbonate for conjugation to lysine residues on antibodies, while the azide group is used to attach cytotoxic payloads via click chemistry.
• PEGylated Nanoparticles: Functionalize liposomes, polymeric nanoparticles, or inorganic nanoparticles with azide groups for subsequent bioorthogonal surface modification, improving colloidal stability and enabling targeted drug delivery.
• Surface Functionalization: Immobilize the hydroxyl terminus onto activated surfaces (e.g., NHS-activated glass slides, gold surfaces via thiol chemistry after derivatization) to create azide-displaying surfaces for oriented protein capture or biosensor fabrication.
• Proteomics and Chemical Biology: Incorporate azide-bearing PEG tags onto small molecules or probes for bioorthogonal labeling experiments in cell lysates or live cells (SPAAC).
• Hydrogel Fabrication: Use azide–alkyne cross-linking to form PEG-based hydrogels with tunable mesh size and mechanical properties for 3D cell culture or controlled drug release.

Quality, Ordering and Regulatory Notes

Purity and Quality: Azido-PEG20-alcohol (A596194) is supplied as a research-grade reagent. Customers requiring specification sheets, certificates of analysis (CoA), or lot-specific purity data should contact Aladdin Scientific customer service or download documents from the product page.

Ordering: Place orders online via the Aladdin Scientific website using SKU A596194, or contact your regional sales representative. Bulk quantities and custom PEG chain lengths may be available upon request.

Shipping and Storage on Receipt: The product is typically shipped with dry ice or cold packs. Upon receipt, transfer immediately to –20 °C storage. Inspect the vial for integrity and confirm the lot number against the CoA before use.

Regulatory Status: This product is intended for research use only (RUO) and is not approved for diagnostic, therapeutic, or veterinary use. Compliance with local regulations regarding azide-containing compounds is the responsibility of the end user.

Frequently asked questions

What solvents are compatible with Azido-PEG20-alcohol?

Azido-PEG20-alcohol is soluble in water and polar organic solvents including DMSO and DMF. For best stability, prepare concentrated stock solutions in anhydrous DMSO or DMF and dilute into aqueous buffers immediately before use. Avoid prolonged storage in aqueous solution to prevent PEG chain hydrolysis.

Can Azido-PEG20-alcohol be used for live-cell labeling?

Yes, Azido-PEG20-alcohol is suitable for live-cell labeling when paired with a cyclooctyne-functionalized partner in a copper-free SPAAC reaction. CuAAC conditions are generally cytotoxic and should be avoided for live-cell applications. Confirm biocompatibility of the buffer system and reagent concentrations before use in cellular experiments.

How should I handle the azide group safely in the laboratory?

Organic azides at the small-molecule research scale pose low explosive risk when handled properly, but precautions are still required. Avoid heating azide-containing solutions above 100 °C, contact with strong reducing agents, or concentration to dryness with heating. Always wear PPE, work in a fume hood where possible, and dispose of azide waste according to local regulations.

What is the difference between Azido-PEG20-alcohol and shorter azido-PEG reagents?

The 20-unit PEG chain in Azido-PEG20-alcohol provides a longer, more hydrophilic spacer compared to shorter PEG variants (e.g., PEG4 or PEG8). This results in improved aqueous solubility of the conjugate, greater steric shielding to reduce immunogenicity or nonspecific binding, and enhanced flexibility between the two conjugated molecules. Shorter PEG linkers may be preferred when minimal spacer length is needed or for applications where mass constraints are important.

How do I confirm successful conjugation using Azido-PEG20-alcohol?

Successful click chemistry conjugation can be confirmed by several analytical methods: MALDI-TOF or ESI mass spectrometry to detect the expected mass shift; gel-shift assay (SDS-PAGE) for protein conjugates; HPLC or SEC to assess purity and conjugation efficiency; and IR spectroscopy to monitor disappearance of the azide stretch at approximately 2100 cm⁻¹.

References

1. Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click Chemistry: Diverse Chemical Function from a Few Good Reactions. Angew. Chem. Int. Ed. 2001, 40, 2004–2021. doi:10.1002/1521-3773(20010601)40:11<2004::AID-ANIE2004>3.0.CO;2-5
2. Agard, N. J.; Prescher, J. A.; Bertozzi, C. R. A Strain-Promoted [3 + 2] Azide–Alkyne Cycloaddition for Covalent Modification of Biomolecules in Living Systems. J. Am. Chem. Soc. 2004, 126, 15046–15047. doi:10.1021/ja044996f
3. Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B. A Stepwise Huisgen Cycloaddition Process: Copper(I)-Catalyzed Regioselective Ligation of Azides and Terminal Alkynes. Angew. Chem. Int. Ed. 2002, 41, 2596–2599. doi:10.1002/1521-3773(20020715)41:14<2596::AID-ANIE2596>3.0.CO;2-4
4. Harris, J. M.; Chess, R. B. Effect of pegylation on pharmaceuticals. Nat. Rev. Drug Discov. 2003, 2, 214–221. doi:10.1038/nrd1033

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.