Thiol PEG, mPEG-SH - ≥95%, MW 550 Da , CAS No.134874-49-0

CAS: 134874-49-0 Cat. No.: T164399 Formula: (C₂H₄O)_nC₃H₈OS EC Number: 881-781-2

GRADE & PURITY ≥95%, MW 550 Da

Synonyms

m-PEG-thiol (MW 550) | mPEG-SH (MW 550)

Storage

Store at -20°C,Argon charged

Shipped In

Ice chest + Ice pads

Overview

Thiol functionalized methoxyl polyethylene glycol, PEG thiol (mPEG-SH) is a monofunctional PEG derivative that can be used to modify proteins, peptides and other materials. Thiol groups also have high affinity to gold surface and are widely used for gold nanoparticles or gold film modification. PEGylation can increase solubility and stability and reduce immunogenicity of peptides and proteins. It can also suppress the non-specific binding of charged molecules to the modified surfaces.

Specifications

Synonyms

m-PEG-thiol (MW 550) | mPEG-SH (MW 550)

Specifications & Purity

≥95%, MW 550 Da

Storage

Store at -20°C,Argon charged

Shipped In

Ice chest + Ice pads

This product requires cold chain shipping. Ground and other economy services are not available.

Purity

≥95%

Names and Identifiers

Isomeric SMILES

COCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOCCS

WGK Germany

3

Alternate CAS

134874-49-0

Chemical and Physical Properties

• Solubility: Off-white/white solid or viscous liquid depends on molecule weight;Soluble in regular aqeous solution as well as most organic solvents
• Sensitivity: Moisture sensitive

Application Protocols

The following literature/general protocols illustrate common uses of mPEG-SH. Adjust for your specific MW, concentrations, and substrates. Always perform small-scale pilots.

1. Maleimide conjugation (aqueous):

• Prepare 50 mM phosphate buffer, pH 6.8–7.0, with 1 mM EDTA; degas thoroughly.
• Dissolve mPEG-SH to 1–10 mM (–SH basis). If necessary, pre-reduce with equimolar TCEP for 15–30 min, then remove excess (desalting column) if incompatible.
• Add maleimide-functional partner (1.0–1.2 eq per –SH). Stir at RT for 1–2 h.
• Quench residual maleimide if needed. Purify by dialysis/UF (cutoff chosen per MW) or SEC. Confirm by 1H NMR/SEC.

2. Gold nanoparticle PEGylation:

• Clean AuNPs; exchange to low-salt water.
• Add mPEG-SH to achieve 0.01–1 mM final (optimize by size and surface area). Gently agitate 1–12 h at RT.
• Salt-age gradually if higher grafting density is required. Purify by centrifugation or diafiltration. Verify stability and PEG grafting by UV-Vis (no aggregation), DLS (hydrodynamic size increase), and XPS (for films).

3. Thiol–ene hydrogel formation:

• Dissolve mPEG-SH and multi-alkene crosslinker in suitable solvent (e.g., PBS or DMSO) with 0.1–0.5 wt% photoinitiator.
• Deoxygenate; cast into molds. Irradiate (e.g., 365 nm) for minutes to gelation.
• Post-cure/rinse to remove unreacted species. Characterize swelling and modulus.

Note: These are non-binding examples. Consult the CoA for –SH content (mmol/g) to set stoichiometry accurately.

Biological Roles

This section summarizes general, literature-based roles of PEG and thiol-functional PEGs in biological contexts. It does not imply clinical use for this item.

• PEG as a stealth polymer (literature/general): Poly(ethylene glycol) is widely used to reduce protein adsorption (antifouling), limit opsonization, and increase hydrodynamic size of macromolecules and particles. Surface-grafted PEG chains form hydration layers that resist nonspecific interactions.
• mPEG-SH for surface modification: The thiol group binds strongly to gold, enabling formation of PEGylated self-assembled monolayers (SAMs) on Au substrates and nanoparticles. Such coatings can modulate colloidal stability and biological interactions by decreasing nonspecific binding.
• Bioconjugation: mPEG-SH reacts chemoselectively with maleimide-bearing biomolecules to form stable thioether linkages under mild, near-neutral conditions compatible with many proteins and enzymes (when properly buffered and oxygen-controlled).
• Redox-responsive assemblies: Disulfide formation/exchange with mPEG-SH can create reversible linkages that respond to reducing environments (e.g., presence of glutathione), useful for stimuli-responsive materials (research context).
• Hydrogels and biomaterials: Thiol–ene/yne chemistries with mPEG-SH provide cytocompatible crosslinking routes to fabricate hydrogels and coatings with tunable mesh size, stiffness, and bioinertness.

Note: The above are general research roles. No medical or clinical claims are made for SKU T164399. Specific performance depends on chain length, grafting density, and end-group fidelity; consult the CoA for item-specific attributes such as average MW and functionality.

Buffer Applications

While mPEG-SH is not a buffering agent, buffer selection is critical for its thiol chemistry in bioconjugation and surface modification. The guidance below is literature/general and offered for practical planning.

• Maleimide–thiol coupling:
  • Recommended buffer: 20–100 mM phosphate or HEPES, pH 6.5–7.2, with 0.1–5 mM EDTA to chelate metals.
  • Rationale: Near-neutral pH maximizes thiol selectivity for maleimide while minimizing amine side reactions and maleimide hydrolysis. EDTA reduces metal-catalyzed oxidation of thiols.
  • Avoid: High pH (>8.0), which increases thiolate formation and accelerates competing reactions and oxidation.
• Disulfide exchange/oxidation:
  • For controlled oxidation to disulfides, use oxygen-limited, mildly basic buffers (pH 7.5–8.0) or enzymatic systems; monitor by Ellman’s assay.
  • For reduction to free thiol, TCEP works well in phosphate buffers across pH ~6–8 and is amine-compatible.
• Protein compatibility:
  • Maintain isotonicity (e.g., 150 mM NaCl) when working with proteins; add 0.01–0.05% nonionic surfactant only if required to prevent aggregation.
• Degassing and oxygen control:
  • Sparge buffers with nitrogen/argon and maintain inert headspace. Prepare fresh to minimize dissolved oxygen.

Note: Buffer composition and concentration may need adjustment based on protein isoelectric point, stability, and the average MW of mPEG-SH (viscosity/solubility considerations).

Green Alternatives

Because mPEG-SH is a polymeric reagent, “green alternatives” focus on greener media and auxiliaries for its use rather than replacing the reagent itself.

Greener media choices (literature/general):

• Prefer water or aqueous buffers for maleimide conjugations, disulfide exchange, and nanoparticle PEGylation. These minimize VOC emissions and simplify workup (dialysis/ultrafiltration).
• When organic solvent is needed (e.g., for high-MW PEG dissolution), choose lower-toxicity solvents such as ethanol or isopropanol where compatible with the reaction/surface process. Validate solubility first.
• Use TCEP instead of DTT or β-mercaptoethanol to reduce odor and volatility and to ease removal in aqueous systems.

Process-intensity and waste reduction:

• Employ stoichiometric planning using –SH mmol/g to avoid large excesses.
• Utilize dialysis/ultrafiltration or precipitation to recover and reuse unreacted PEG where purity requirements allow.
• Conduct reactions at ambient temperature to reduce energy consumption; PEG thiol reactions (e.g., maleimide) typically proceed efficiently at room temperature.

Comparison snapshot (literature/general):

• Water/buffer: Highest EHS profile; requires oxygen exclusion and may need chelators. Minimal solvent waste.
• Ethanol/isopropanol: Renewable routes available; flammable but lower chronic toxicity than DMF/DMSO; may limit solubility for higher MWs.
• DMSO/DMF: Excellent solvation and anhydrous handling; higher EHS burden; ensure proper waste segregation.

Note: The reagent identity (mPEG-SH) is often essential (e.g., Au–S binding); replacing it with alternative functionalities may change performance fundamentally.

Pharmaceutical Uses

No therapeutic or clinical claims are made for this item. The following describes formulation and process roles of mPEG-SH in research and manufacturing contexts (literature/general):

• Surface PEGylation of devices and particulates: mPEG-SH can be used to modify gold-coated components and nanoparticles, imparting protein resistance and improved colloidal stability in process streams and analytical devices.
• Intermediate for conjugates: The thiol end-group enables coupling to maleimide-bearing linkers or actives to prepare PEGylated intermediates that may be further processed in R&D-scale formulation development.
• Materials for controlled release matrices: Thiol–ene crosslinking of mPEG-SH can generate hydrogels and coatings used in research prototypes for depot systems and device coatings; PEG provides hydration and diffusional control.
• Excipient considerations: While many PEGs are compendial excipients, functionalized PEGs like mPEG-SH are generally specialty reagents. If excipient-grade attributes (e.g., pharmacopeial compliance, bioburden/endotoxin limits) are required, they must be explicitly specified on the CoA/specification—no such claims are made for SKU T164399.
• Processing benefits: PEGylation can increase aqueous solubility, modulate viscosity, and reduce non-specific adsorption on process equipment and analytical surfaces.

For regulated applications, verify grade, residuals, endotoxin/bioburden, elemental impurities, and change control with the supplier. For this item, grade/purity are not specified; refer to CoA/Spec Sheet.

Physical Properties

Item-specific numerical specifications (bp, mp, density, etc.) are not provided for this polydisperse polymer.

• Appearance: Not specified for this item; refer to CoA/Spec Sheet. (General: PEGs appear as white solids, waxy solids, or viscous oils depending on average MW.)
• Molecular weight distribution: Not specified for this item; refer to CoA/Spec Sheet. (General: polymers are characterized by Mn, Mw, and PDI.)
• Solubility (literature/general):
  • Highly soluble in water and many polar organic solvents (e.g., methanol, ethanol, DMF, DMSO). Solubility in acetone and acetonitrile varies with MW; low-MW grades are more miscible.
  • Insoluble or poorly soluble in nonpolar solvents (e.g., hexanes, toluene) unless MW is very low.
• Partitioning (literature/general): PEG chains are hydrophilic; mPEG exhibits low logP and high water affinity. Thiol end-group does not significantly reduce aqueous solubility.
• pKa (literature/general): The terminal thiol typically exhibits pKa ~8–10 depending on microenvironment; thiolate formation increases at basic pH, which can accelerate oxidation or side reactions.
• Thermal behavior (literature/general): Glass transition and melting behavior depend strongly on MW; lower-MW mPEGs often show defined melting transitions (ca. 40–65 °C range), while higher MWs exhibit broadened or semi-crystalline behavior.
• Viscosity (literature/general): Aqueous/organic solutions can be viscous at high concentrations and higher MW.

Note: For precise, lot-specific values (e.g., average MW, PDI, residual solvents, water content), refer to the CoA/Spec Sheet for SKU T164399.

Quality and Grades

• Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.

How this product class is typically qualified (literature/general):

• Average molecular weight and distribution: Reported as Mn and/or Mw with polydispersity index (PDI = Mw/Mn). For functional PEGs, a narrow PDI improves batch-to-batch reproducibility in bioconjugation and materials assembly.
• Functional end-group content: Thiol functionality is commonly quantified by Ellman’s assay (DTNB) or NMR end-group analysis. Reporting as mmol –SH per gram is useful for stoichiometric planning.
• Residual solvents/volatiles and water: Karl Fischer for water; GC for residual solvents. Low levels reduce hydrolysis/oxidation risk and improve conjugation efficiency.
• Metal content: Trace metal analysis (e.g., ICP-MS) may be reported when materials will contact proteins, nanoparticles, or catalysts sensitive to metals.
• Identity and purity by NMR/IR: 1H/13C NMR confirm PEG backbone and end-groups; IR shows diagnostic S–H stretch (~2550–2600 cm−1, weak) and C–O–C stretches of PEG.
• Bioburden/endotoxin (if intended for sensitive bio-uses): Some suppliers offer low bioburden or endotoxin-tested lots; not implied for this item unless specified on CoA.

Implications for use:

• High end-group fidelity and known –SH content enable accurate stoichiometry in maleimide coupling and Au-surface functionalization.
• Lower PDI enhances self-assembled monolayer (SAM) order on metals and narrows hydrodynamic size distributions for nanoparticle coatings.

For SKU T164399, please consult the CoA/Spec Sheet for the actual MW, PDI, functional content, and any analytical limits.

Reaction and Applications

mPEG-SH is a versatile, thiol-functional polyethylene glycol used widely for conjugation and surface modification.

Key application families (literature/general):

• Michael addition to maleimides: Rapid, chemoselective conjugation at pH ~6.5–7.2 to yield stable thioether linkages. Useful for PEGylating maleimide-functional small molecules, polymers, or biomolecules.
• Thiol–ene/thiol–yne click reactions: Radical-mediated addition to vinyls/allyls/alkynes with photoinitiators or thermal initiators to build networks, hydrogels, and surface coatings.
• Disulfide formation/exchange: Oxidative coupling with other thiols to form reversible disulfide linkages; reductant-controlled (TCEP/DTT) strategies allow dynamic assembly.
• Metal surface binding: Strong Au–S coordination on gold forms self-assembled monolayers (SAMs); PEG imparts protein resistance and colloidal stability to nanoparticles.
• Protein/nanoparticle PEGylation: Endows stealth behavior, reduces nonspecific adsorption, improves colloidal stability, and tunes hydrodynamic size.

Practical tips:

• Preserve the free thiol: Work under inert atmosphere with degassed solvents/buffers. If necessary, pre-reduce with TCEP (odorless, phosphate-compatible) shortly before coupling; remove excess reductant if incompatible with the partner functionality.
• Control stoichiometry by –SH content (mmol/g) from the CoA.
• Include 0.1–5 mM EDTA to chelate trace metals that catalyze thiol oxidation.
• For SAM formation, thoroughly clean gold (e.g., plasma/UV-ozone) and soak in mPEG-SH solution (μM–mM range, solvent-dependent) to achieve densely packed, protein-resistant monolayers.
• For thiol–ene, deoxygenate, use suitable photoinitiator (e.g., Irgacure-type) and monitor conversion by disappearance of alkene signals (NMR/IR).

Reaction Conditions

Typical, literature-based conditions are summarized below for planning purposes. Optimize for your specific substrates and the average MW of mPEG-SH.

• Maleimide–thiol conjugation:
  • Solvent/buffer: 20–100 mM phosphate or HEPES, pH 6.5–7.2; 0.1–5 mM EDTA.
  • Concentration: 0.1–10 mM in –SH (depending on solubility and partner stoichiometry).
  • Temperature/time: Ambient (20–25 °C), 0.5–2 h for small molecules; longer for sterically hindered systems.
  • Notes: Degas solutions; avoid >pH 7.5 to limit maleimide hydrolysis. Quench unreacted maleimide if needed (e.g., with cysteine).
• Thiol–ene (radical) coupling:
  • Solvent: DMSO, MeOH, water (if photoinitiator-compatible), or neat for film formation.
  • Initiation: UV (e.g., 365 nm) with type I photoinitiator; 0.1–1 wt% initiator relative to total monomer.
  • Temperature/time: Room temperature to 60 °C; minutes to hours depending on light intensity and conversion.
  • Notes: Deoxygenate to reduce radical quenching; monitor by FTIR (alkene disappearance).
• Disulfide formation:
  • Conditions: Air oxidation in buffer pH 7–8 or mild oxidants (e.g., diamide); monitor by Ellman’s assay.
  • Time: Hours to overnight; stirring with limited headspace oxygen gives controllable rates.
• Gold surface functionalization:
  • Solvent: Ethanol, water, or mixtures; typical mPEG-SH 0.01–1 mM.
  • Time: 1–24 h soak at ambient; rinse thoroughly to remove physisorbed polymer.
  • Notes: Clean gold surfaces increase SAM order; mixed SAM formulations adjust density/functional presentation.

Expected conversions/yields: High conversions are typical under optimized conditions; verify by appropriate analytics (UV-Vis for nanoparticles, SEC/HPLC, NMR, XPS/ellipsometry for surfaces).

Safety and Handling

Hazard information specific to this item is not provided. Always consult the SDS for authoritative guidance.

• GHS classification: Not specified for this item; refer to SDS.
• Signal word / H-statements / pictograms: Not specified for this item; refer to SDS.

General laboratory safety (polyether- and thiol-functional polymers):

• PPE: Wear lab coat, appropriate chemical-resistant gloves (e.g., nitrile), and safety glasses. Use in a fume hood when weighing or dissolving to minimize exposure to dust/aerosols.
• Incompatibilities: Avoid strong oxidizers (thiols can oxidize to disulfides). Prolonged exposure to air and light can promote thiol oxidation; exclude oxygen with inert gas where feasible. Strong bases form thiolates, which are more reactive and air-sensitive.
• Handling notes: Degas buffers/solvents to limit oxidation. For conjugation, include a metal chelator (e.g., EDTA) to minimize metal-catalyzed thiol oxidation (general practice). Minimize headspace oxygen in storage vials.
• First aid (general): In case of skin contact, wash with soap and water. For eye contact, rinse cautiously with water for several minutes; remove contact lenses if present and easy to do. If inhaled (dust/aerosol), move to fresh air. If ingested, rinse mouth; seek medical advice in all cases. Refer to SDS for details.
• Waste: Collect polymer-containing aqueous/organic solutions in appropriate containers. Avoid drain disposal. Follow institutional and local regulations.

Storage from Product Data: Store at −20 °C under argon; shipment on ice packs. Maintain containers tightly sealed; allow to reach room temperature in a dry environment before opening to prevent moisture ingress.

Solvent Selection

This product is a polymeric reagent rather than a solvent. The following guidance addresses solvent choice for dissolving and reacting mPEG-SH.

General polarity/miscibility (literature/general):

• Aqueous systems: Readily soluble in water and buffered saline across a wide pH range. Best practice for thiol stability is mildly acidic to neutral buffers (pH ~6.5–7.2) to limit thiolate formation and oxidation.
• Polar organics: Dissolves well in DMSO and DMF; low-to-mid MW grades dissolve in methanol/ethanol. Solubility in acetonitrile and acetone depends on MW; test on small scale.
• Nonpolar solvents: Limited solubility; if necessary, co-solvent strategies (e.g., small % DMSO) can help, but avoid conditions that promote oxidation.

Selection considerations:

• For bioconjugation to maleimides: Use degassed phosphate or HEPES buffer, pH 6.8–7.2, with 0.1–5 mM EDTA to chelate adventitious metals. Avoid high pH which forms thiolate and can accelerate maleimide ring opening.
• For surface chemistry (Au–S): Alcohols or water are acceptable; ensure clean substrates and minimal oxygen for dense monolayers.
• For thiol–ene reactions: Use solvents compatible with photoinitiators (e.g., DMSO, MeOH, or neat if melt-processable), and control oxygen to reduce radical quenching.

Brief comparison (literature/general):

• Water/buffer: Green, biocompatible; best for protein and nanoparticle work. Requires oxygen control to limit oxidation.
• DMSO/DMF: Strong solvents for high-MW PEG; enable anhydrous conditions. Less green; ensure thorough removal post-reaction by dialysis or precipitation.
• Alcohols: Convenient for surface prep; volatility aids drying but may affect assembly kinetics.

Storage and Reconstitution

From Product Data:

• Storage conditions: Store at −20 °C, argon charged.
• Shipping: Ice chest + ice pads.
• Research use note: For research use only.

Best practices (literature/general):

• Container and atmosphere: Keep tightly sealed under inert gas (argon or nitrogen). Include desiccant to limit moisture. Allow the vial to warm to room temperature in a dry environment before opening to avoid condensation.
• Light/oxygen: Protect from light where practical and minimize oxygen exposure to preserve free thiol. Consider aliquoting under inert gas to reduce repeated headspace oxygen exposure.
• Reconstitution/solubilization:
  • Aqueous: Use degassed, oxygen-reduced buffers (e.g., phosphate or HEPES, pH 6.5–7.2) with 0.1–1 mM EDTA. Prepare fresh solutions immediately prior to use.
  • Organic: Dissolve in anhydrous DMSO or DMF under inert atmosphere for moisture/oxygen-sensitive applications. Filter if necessary (0.22 μm) to remove particulates.
• Stability:
  • Solid state: Typically stable at −20 °C under inert gas for extended periods; confirm retest/expiry on CoA.
  • In solution: Use promptly (same day) to minimize thiol oxidation. If storage is unavoidable, keep cold, inert, and dark; expect gradual disulfide formation.
• Quality checks before use: Assess free thiol content (e.g., Ellman’s assay) if material has been stored for long periods. Inspect for discoloration/viscosity changes.

For any item-specific shelf life, residual solvents, water content, or stabilizers: Not specified for this item; refer to CoA/Spec Sheet.

Structure and Identity

Thiol PEG (mPEG-SH) is a methoxy-terminated poly(ethylene glycol) bearing a single terminal thiol (–SH) at the opposite end. It is a polydisperse, linear polyether functionalized for thiol-based conjugation.

• Product name: Thiol PEG, mPEG-SH
• CAS: 134874-49-0
• InChIKey: Not specified for this item; refer to CoA/Spec Sheet.
• SMILES: Not specified for this item; refer to CoA/Spec Sheet. Note: canonical SMILES/InChI are generally not uniquely defined for polydisperse polymers.
• Molecular formula: Not specified for this item; refer to CoA/Spec Sheet. (General: repeat unit of PEG is –CH2–CH2–O–, i.e., (C2H4O)n, capped with –OCH3 and –CH2–CH2–SH end-groups.)
• Molecular weight: Not specified for this item; refer to CoA/Spec Sheet. (Literature: mPEG-SH is commonly supplied in a range of nominal average molecular weights, e.g., ~1–20 kDa.)

Structural features (general description):

• Backbone: linear polyether comprised of ethylene oxide repeat units (–CH2–CH2–O–)n.
• End groups: one terminus is methoxy-capped (–O–CH3), the other bears a primary thiol (–CH2–CH2–SH or analogous spacer to the PEG chain).
• Functional group chemistry: a single nucleophilic/soft Lewis base thiol suitable for Michael addition (e.g., to maleimides), thiol–ene/yne reactions, disulfide formation/exchange, and strong Au–S coordination to gold surfaces.
• Physical form: typically solid or viscous semi-solid depending on average molecular weight (general literature).

Synthetic Utility

From a synthetic perspective, mPEG-SH serves as a monofunctional, nucleophilic, soft sulfur handle appended to a hydrophilic polymer chain, enabling a broad range of transformations (literature/general):

• Chemoselective thiol addition: Efficient Michael addition to maleimides, acrylates, vinyl sulfones, and other activated alkenes provides stable thioether linkages under mild, aqueous conditions, preserving sensitive motifs.
• Radical thiol–ene/yne coupling: Under UV or thermal initiation, the –SH adds across alkenes/alkynes to construct networks, graft copolymers, and surface coatings with high conversion and spatial control (photopatterning).
• Disulfide chemistry: Oxidative coupling to yield PEG–S–S–R linkages enables reversible, redox-responsive conjugates; disulfide exchange allows dynamic covalent assembly.
• Nucleophilic substitutions: As a thiolate (generated in situ with base), it can undergo SN2 with suitable electrophiles (e.g., alkyl halides/mesylates) to furnish thioethers, though sterics/solubility of high-MW PEG must be considered.
• Metal surface coordination: Strong Au–S interactions allow creation of densely packed PEG monolayers on gold; mixed SAMs (e.g., mPEG-SH + functional alkanethiols) tune surface energy and ligand display.

Practical considerations:

• Control stoichiometry using –SH mmol/g from the CoA for predictable grafting densities.
• Maintain oxygen exclusion to suppress disulfide formation prior to coupling.
• Choose solvent to match the partner’s solubility; water/HEPES/phosphate for bioconjugation, DMSO/DMF for small-molecule/electrophile couplings, alcohols/water for SAMs.
• Purification typically by dialysis/ultrafiltration (bioconjugates), precipitation (polymer reactions), or SEC (analytical).

Target Specificity

Not applicable. This product is a small-molecule/polymer reagent, not a biological targeting agent or antibody. No antigen, epitope, clone, isotype, or species reactivity information applies.

Frequently Asked Questions

What is the purity of this product?

This product is supplied at ≥95% purity (chemical assay). Lot-specific values are stated on the Certificate of Analysis.

How should this product be stored?

Store at ?20 °C under argon. It is supplied under an argon blanket; reseal under inert gas after each use.

How is this product shipped?

This product ships in an insulated container with ice pads. Unpack on arrival and transfer it to the storage condition stated above.

What are the CAS number, molecular formula and molecular weight?

The CAS Number is 134874-49-0, the molecular formula is (C2H4O)nC3H8OS.

What documentation is provided?

Available product documentation, including Certificates of Analysis (COA), Safety Data Sheets (SDS), and specification sheets, is shown in the product document area. Document availability and access follow the current site policy.