4arm-PEG40K-COOH - average Mₙ 40,000 , CAS No.A478160

CAS: A478160 Cat. No.: A478160 Formula: C(CH₂O(CH₂CH₂O)nCH₂COOH)₄

GRADE & PURITY average Mₙ 40,000

Synonyms

4arm-PEG-COOH, 4arm-PEG-Carboxyl

Storage

Store at -20°C,Argon charged

Shipped In

Ice chest + Ice pads

Panoramica

Description

4arm PEG Carboxyl. Hydrogel PEG. Carboxyl group binds to amino or other acid reactive chemical groups.Applications may include: bioconjugation, drug delivery, PEG hydrogel, crosslinker, and surface functionalization

Specifications

Sinonimi

4arm-PEG-COOH, 4arm-PEG-Carboxyl

Specifiche e purezza

average Mₙ 40,000

Condizioni di conservazione di stoccaggio

Store at -20°C,Argon charged

Spedito in

Ice chest + Ice pads

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Proprietà chimiche e fisiche

• Sensibilità: Moisture sensitive

Application Protocols

No vendor‑verified protocols are provided in the Product Data for this item. The following are general, illustrative steps for common research uses; adjust to your system.

• Example: EDC/sulfo‑NHS coupling of 4arm‑PEG‑COOH to an amine‑functional surface (general)

  1. Dissolve polymer at 5–20 mg/mL in MES buffer (0.1 M, pH 5.5).
  2. Add NHS (0.1 M) and EDC (0.2 M) stocks to achieve ~1 eq NHS and 1–1.5 eq EDC per –COOH; incubate 15–20 min at RT.
  3. Transfer to amine‑functional substrate (e.g., APTES‑silica) and incubate 1–2 h at RT with gentle agitation.
  4. Rinse thoroughly with buffer; quench remaining active esters with 50 mM ethanolamine (pH 8.5) for 15 min; rinse.

• Example: Hydrogel crosslinking with gelatin (general)

  1. Dissolve gelatin (type A/B) in PBS (pH 7.4) at 37–40 °C; dissolve 4arm‑PEG‑COOH in MES (pH 5.5).
  2. Activate PEG with EDC/NHS 10–15 min; mix with gelatin to desired stoichiometry (amines:carboxyl ≈ 1–2:1).
  3. Allow gelation at RT–37 °C; adjust buffer strength and polymer content to tune mechanics.

• Quality control

  • Verify coupling by surface water contact angle change, XPS, or dye‑labeled amine probes. For gels, measure storage modulus (G′) via rheology.

Biological Roles

PEG is not a natural metabolite; it is considered biologically inert and hydrophilic, forming a dense hydration shell that reduces nonspecific biomolecular interactions (general literature). The 4‑arm carboxylated variant enables covalent attachment to biomolecules and surfaces via amide linkages.

• General biochemistry context (literature)

  • Protein resistance: PEG layers reduce protein adsorption through steric repulsion and water structuring, improving anti‑fouling behavior on surfaces and nanoparticles.
  • Charge state: At physiological pH, terminal –COOH groups may be partially deprotonated (–COO−), introducing limited anionic character that can influence colloidal stability and bio‑interface behavior.
  • Multivalency: The 4‑arm architecture allows multivalent presentation of ligands or attachment points for proteins/peptides, impacting avidity in receptor‑ligand systems when used in research models.
  • Hydration and flexibility: Ether oxygens form hydrogen bonds with water, maintaining chain mobility and a brush‑like barrier.

• Cautions

  • Avoid over‑interpretation: Any biological effects depend on conjugates, densities, and geometry; this product is for research use only.
  • Endotoxin/bioburden: For sensitive biological assays, verify low endotoxin/bioburden on the CoA or perform user‑side depyrogenation/sterile filtration.

• Typical research uses

  • Creating antifouling coatings, passivating biosensor surfaces, preparing PEGylated model constructs, and forming hydrogels for in vitro studies.

Buffer Applications

This product is not a buffering reagent. However, its –COOH groups participate in pH‑dependent chemistries that require appropriate buffers.

• Practical guidance (general)

  • EDC/NHS activation: Use mildly acidic buffers (e.g., MES, pH 5.0–6.0) for activation; perform amide coupling near pH 7.0–8.0 (e.g., phosphate or HEPES) to favor reaction with amines.
  • Avoid buffers containing primary amines (e.g., Tris, glycine) during activation/coupling as they will compete and consume activated esters.
  • Ionic strength: Moderate salt (50–150 mM NaCl) can improve solubility and reduce nonspecific electrostatic interactions in conjugation workflows.

• Viscosity considerations

  • PEG significantly increases solution viscosity; ensure adequate mixing and consider slower addition of co‑reactants.

• Preparation tips

  • Dissolve polymer in the chosen buffer with gentle stirring; filter sterilize (0.22 µm) for cell‑adjacent in vitro applications if required. Calculate functional equivalents per mL from the acid number or end‑group analysis on the CoA.

Green Alternatives

Sustainability considerations primarily concern solvent choice, coupling reagents, and purification strategies rather than the PEG backbone itself.

• Greener process choices (general)

  • Solvents: Prefer water or water/ethanol systems for EDC/sulfo‑NHS coupling when feasible. Replace DMF with DMSO or propylene carbonate where compatible.
  • Coupling agents: EDC is water‑soluble and generates urea byproducts; avoid DCC (insoluble dicyclohexylurea waste). Enzymatic ligation (e.g., microbial transglutaminase for protein substrates) can be an alternative pathway.
  • Purification: Favor aqueous dialysis and precipitation over extensive chromatographic purification to minimize solvent consumption.

• Alternative polymers (application‑dependent, literature)

  • Polyglycerol (hyperbranched), polysarcosine, or zwitterionic polymers can offer similar antifouling performance; tradeoffs include different degradation profiles and coupling chemistries.
  • Biodegradable backbones (poly(ethylene glycol)‑co‑polyesters, PLA‑PEG) if long‑term environmental persistence is a concern.

• Comparison snapshot (general)

  • 4‑arm PEG‑COOH vs linear PEG‑COOH: The 4‑arm architecture reduces solution viscosity at a given Mw and increases multivalency, potentially lowering total polymer mass needed for a given crosslink density.
  • Water‑based EDC/NHS vs anhydrous acid chloride routes: Aqueous carbodiimide chemistry is milder, safer, and generates more benign waste, at the cost of potential hydrolysis and need for pH control.

• Practical tips

  • Implement mass balance and solvent recycling for DMF/DMSO operations. Use room‑temperature processes where possible; gentle heating only for dissolution.

Pharmaceutical Uses

For research and process development use only. No clinical or therapeutic claims are made for this product.

• General formulation roles of PEG‑COOH (literature)

  • Excipient/prototyping: As a hydrophilic polymer component in experimental depot systems, in situ forming gels, or as a viscosity modifier in R&D formulations.
  • Surface modification: Carboxyl termini enable covalent attachment to amine‑bearing ligands or surfaces for prototyping stealth coatings on particles or devices in preclinical research settings.
  • Conjugation handle: Provides a platform to prepare model PEGylated conjugates via amide linkages for analytical method development.

• Considerations for development work

  • Trace impurities (residual solvents, catalysts, low‑MW PEG) can impact biocompatibility; verify via CoA and perform additional purification if needed.
  • End‑group fidelity is critical to dose reproducibility in conjugation workflows; confirm by NMR/acid value.
  • Solution handling: Prepare with sterile techniques when used near biological systems; consider endotoxin testing.

• Regulatory status

  • Pharmacopeial status and compliance are not specified for this item; refer to CoA/Spec Sheet. Any use in manufacturing or clinical contexts would require additional qualification beyond the scope of this listing.

Physical Properties

• Item-specific (from Product Data)

  • Appearance: Not specified for this item; refer to CoA/Spec Sheet.
  • Molecular weight: Not specified for this item; refer to CoA/Spec Sheet (name implies ~40 kDa nominal).

• General/literature characteristics for ~40 kDa star-PEG‑COOH (not item specifications)

  • Physical state: Typically a white to off‑white solid; waxy/semicrystalline polymer.
  • Melting behavior: PEGs show broad melting transitions; high‑MW PEGs often soften/melt in the ~50–65 °C range (literature), dependent on crystallinity and end‑groups.
  • Glass transition (Tg): Around −60 to −50 °C for PEG backbones (literature); end‑groups and architecture can shift Tg slightly.
  • Solubility profile (literature)
    • Water: Freely soluble; solubility enhanced above pH ~6 as carboxylates ionize.
    • Polar organics: Soluble in DMSO, DMF, NMP; soluble/miscible in lower alcohols (MeOH, EtOH) to varying degrees.
    • Aprotic, less polar: Limited solubility in acetone/ACN; poor in ethers and alkanes.
  • pKa (terminal –COOH): Typical aliphatic carboxyl pKa ~4–5 (literature); local microenvironment in PEG can shift apparent pKa modestly.
  • Density: Bulk density varies with lot and packing; true density of PEG solids ~1.1–1.2 g/mL (literature estimate).
  • Viscosity (solutions): Strongly concentration‑ and temperature‑dependent; 10–20 wt% aqueous solutions are markedly viscous at room temperature.

• Notes

  • Exact thermal transitions, water content, and polydispersity index are lot‑dependent and must be taken from the CoA/Spec Sheet for this item.

Quality and Grades

• Item-specific (from Product Data)

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

• How to interpret quality for star‑PEG‑COOH (general guidance)

  • Key quality attributes for multiarm PEGs typically include:
    • Average molecular weight (Mn) and weight‑average (Mw), plus dispersity (Ð = Mw/Mn).
    • End‑group conversion (>95–99% desired for bioconjugation), often reported as acid value or via NMR integration.
    • Residual solvents/volatiles and water content (Karl Fischer).
    • Inorganic/metal residues from polymerization catalysts (ICP), if applicable.
    • Bioburden/endotoxin if the material is intended for sensitive bio‑applications (not specified here).
  • HPLC/SEC characterization
    • SEC/GPC with multi‑angle light scattering (MALS) provides absolute Mw and Ð and can reveal low‑MW impurities.
  • UV profile
    • PEG lacks strong chromophores; low UV absorbance is typical unless bearing aromatic impurities or activated esters.

• Stabilizers/additives

  • Not specified for this item; refer to CoA/Spec Sheet. Many PEGs are supplied additive‑free; some lots may include trace antioxidants or acid stabilizers depending on synthesis.

• Practical note

  • For sensitive coupling chemistry and reproducible rheology, consult the Lot‑specific CoA to confirm Mn/Mw, Ð, and end‑group conversion. If working under regulatory frameworks, request additional documentation (residual solvent, metals, bioburden) as needed.

Reaction and Applications

This 4‑arm, carboxyl‑terminated PEG is a versatile macromolecular scaffold for materials science and bioconjugation.

• Materials and polymer applications (general)

  • Hydrogel formation: Crosslink with multi‑amine counterparts (e.g., 4‑arm PEG‑NH2, gelatin, lysine‑rich proteins) via EDC/NHS‑mediated amide formation for covalently crosslinked networks.
  • Surface modification: Graft to amine‑functional surfaces (silica, nanoparticles, membranes) to impart protein resistance and hydrophilicity.
  • Nanoparticle stabilization: Provide steric stabilization and colloidal control; carboxylates enable further conjugation.
  • Spacer/branching unit: Four termini enable multivalent ligand display or dendritic growth.

• Bioconjugation chemistries (general)

  • Carbodiimide coupling: EDC with NHS or sulfo‑NHS to form active esters, reacting with primary amines to yield amide bonds (optimal pH ~5–7 for activation; coupling near pH 7–8).
  • Acid chloride route: Convert –COOH to acid chlorides (e.g., oxalyl chloride) in anhydrous media, then couple to alcohols/amines—used sparingly due to harshness and polymer sensitivity.
  • Uronium reagents: COMU/HATU in DMF for efficient amidation with minimal racemization (if peptides are partners).

• Practical tips

  • Dry polymer (vacuum, room temp) prior to moisture‑sensitive activations. Determine equivalents per arm from lot‑specific acid value or NMR.
  • Remove low‑MW byproducts by precipitation or dialysis (MWCO ~10–50 kDa depending on arm length and desired cutoff).
  • Avoid excessive activation times to limit O‑acyl urea formation and hydrolysis; prepare NHS esters immediately before use.

Reaction Conditions

General literature guidance for converting 4arm‑PEG‑COOH into amide/ester derivatives. These are typical conditions, not item specifications—optimize for your system.

• EDC/NHS amidation (aqueous)

  • Solvent/buffer: MES, pH 5.0–6.0 for activation; add NHS (0.8–1.2 eq per –COOH) and EDC (1.0–1.5 eq per –COOH). Activate 10–30 min at RT.
  • Coupling: Add amine nucleophile in phosphate or HEPES, pH 7.2–7.8; use 1.5–5 eq amine per –COOH. React 1–4 h at RT (or overnight at 4 °C for sensitive biomolecules).
  • Quench: Add ethanolamine or Tris after coupling to cap residual active esters.

• Amidation (organic media)

  • Solvent: DMF or DMSO, anhydrous. Reagents: HATU/COMU (0.9–1.2 eq per –COOH), DIPEA (2–4 eq). Temperature: 20–30 °C, 2–12 h.

• Esterification

  • Carbodiimide/DMAP in anhydrous DMF or DCM/DMF; mild warming (25–40 °C). Monitor to limit transesterification/degradation.

• Purification and analysis

  • Precipitate into acetone or IPA, or dialyze against water/appropriate buffer (MWCO selected relative to arm length and conjugate size).
  • Characterize by 1H NMR (end‑group integration), SEC/GPC (Mw, Ð), and TNBS or ninhydrin for residual amines (post‑coupling).

• Notes

  • Maintain low bioburden in aqueous steps; sterile‑filter if needed.
  • Highly concentrated PEG solutions are viscous; ensure efficient mixing and consider overhead stirring.

Safety and Handling

• Item-specific hazard information (from Product Data)

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

• General safety considerations for PEG‑COOH polymers (literature/practice)

  • PEGs are generally regarded as having low acute toxicity and low volatility. Terminal carboxylic acids can cause mild skin/eye irritation.
  • Avoid inhalation of dust; handle powders in a fume hood or ventilated enclosure to minimize aerosol formation.
  • PPE: Lab coat, safety glasses, and disposable nitrile gloves. For weighing/milling, consider dust mask/respirator per institutional EHS guidance.
  • First aid (overview; refer to SDS for authoritative guidance)
    • Eyes: Rinse cautiously with water for several minutes; remove contact lenses if present and easy to do; seek medical attention if irritation persists.
    • Skin: Wash with soap and water; remove contaminated clothing.
    • Inhalation: Move to fresh air; seek medical attention if symptoms develop.
    • Ingestion: Rinse mouth; do not induce vomiting; seek medical attention as needed.
  • Incompatibilities: Strong oxidizers; strong bases/acids can hydrolyze ester linkages if derivatives are formed. Deprotonated carboxylates can chelate metals; avoid unintended complexation in formulations.
  • Thermal hazards: Avoid overheating; polymers can degrade, discolor, or form aldehyde/acidic fragments upon prolonged heating.

• Storage and stability

  • Store at −20 °C under inert gas (argon) as specified. Protect from moisture; cap tightly. For solutions, add a biocide (e.g., 0.02% sodium azide) for short‑term refrigerated storage if compatible with downstream use.

Solvent Selection

4arm‑PEG40K‑COOH behaves as a hydrophilic, polar macromolecule with ionizable termini.

• Miscibility/solubility (literature/general)

  • Water: High solubility; deprotonation above pH ~6 increases solubility and chain expansion.
  • Polar aprotics: DMSO, DMF, NMP readily dissolve this polymer at room temperature.
  • Alcohols: EtOH/MeOH often dissolve at moderate temperatures; isopropanol can be used for precipitation.
  • Poor/limited: Ethers (THF, MTBE) and alkanes; acetone and acetonitrile may produce partial swelling/precipitation.

• Selection guidance

  • For carbodiimide coupling (EDC/NHS) to amines: Use aqueous buffers (pH 5–6 MES) or mixed water/DMF to balance solubility and control hydrolysis.
  • For esterification with alcohols: Anhydrous polar aprotics (DMF, DCM/DMF mixtures) with coupling agents; avoid excessive water.
  • For purification: Precipitate from water into acetone, IPA, or ether; or from DMF/DMSO into MTBE/ether to remove small molecules.

• Small comparison (general)

  • Water vs DMF: Water supports EDC/NHS with minimal organic waste; DMF enhances solubility of hydrophobic co‑reactants but increases workup burden.
  • DMSO vs DMF: DMSO has higher boiling point and is greener by some metrics; DMF offers lower viscosity and easier removal.

• Practical tips

  • Warm viscous solutions gently (≤40 °C) to aid dissolution. Filter through 0.22–0.45 µm to remove particulates. Degas for oxygen‑sensitive co‑reactants if needed.

Storage and Reconstitution

• Item-specific (from Product Data)

  • Storage conditions: Store at −20 °C, argon charged.
  • Shipping: Ice chest + ice pads.

• General handling and stability (polymer best practices)

  • Protect from moisture; allow container to warm to room temperature in a desiccator before opening to prevent water condensation.
  • Reseal under inert gas after use. For long‑term storage, keep in a desiccator or dry cabinet at −20 °C.
  • Avoid repeated temperature cycling; if aliquots are needed, subdivide solid under dry conditions.

• Reconstitution guidance (general)

  • Aqueous: Add to water or buffer with gentle stirring. For EDC/NHS workflows, prepare at 1–50 mg/mL depending on application; adjust pH as required. Filter (0.22–0.45 µm) if clarity is needed.
  • Organic: Dissolve in DMF or DMSO for anhydrous reactions; warm gently (≤40 °C) to aid dissolution.
  • Bioburden control: For short‑term storage of aqueous solutions (days to a week), refrigerate (2–8 °C) and consider 0.02% sodium azide if compatible. For longer storage, freeze at −20 °C; avoid repeated freeze–thaw by aliquoting.

• Stability notes

  • PEG backbones are generally robust; terminal –COOH can undergo slow side reactions if stored in high‑pH solutions. Store solutions near neutral pH and avoid strong oxidants.
  • Lot‑specific water content and residual solvents are not specified for this item; refer to CoA/Spec Sheet.

Structure and Identity

A 4‑arm, star‑shaped polyethylene glycol (PEG) bearing terminal carboxylic acid groups on each arm; nominal average molecular weight ~40 kDa (per product name; confirm actual Mn/Mw on the CoA).

• Item-specific (from Product Data)

  • SKU: A478160
  • Product name: 4arm‑PEG40K‑COOH
  • Storage: −20 °C, argon charged; shipped on ice with ice pads
  • CAS: Not specified for this item; refer to CoA/Spec Sheet (internal SKU: A478160)
  • Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.
  • Molecular formula: Not specified for this item; refer to CoA/Spec Sheet.
  • Molecular weight: Not specified for this item; refer to CoA/Spec Sheet (name indicates ~40,000 g/mol average).

• Structural description (general/literature)

  • Architecture: 4‑arm star PEG with a central, typically pentaerythritol‑type core (literature) from which four poly(ethylene oxide) chains emanate.
  • End groups: Each arm terminates in a carboxylic acid (–COOH) functionality suitable for amide/ester formation after activation (e.g., EDC/NHS).
  • Repeat unit: –CH2–CH2–O– (ethylene oxide) repeated to achieve the desired arm length; polydisperse (Ð > 1; exact Ð per CoA).
  • Stereochemistry: Achiral repeat units; no defined stereocenters.
  • Representation: Polymers generally do not have a single SMILES/InChIKey. SMILES/InChIKey: Not applicable for this polymeric material.

• 2D structure in words

  • A central quaternary carbon (core) connects four PEG chains (flexible ether backbone) ending with –O–C(=O)–OH moieties. The polymer is nonionic overall under acidic/neutral conditions, becoming polyanionic when deprotonated at basic pH.

Synthetic Utility

4arm‑PEG40K‑COOH functions as a multivalent, macromolecular carboxylic acid—useful as a crosslinker, spacer, or soluble support in synthesis.

• Functional group reactivity (general)

  • –COOH → activated esters (NHS/sulfo‑NHS) for amide coupling to primary amines.
  • –COOH → acid chlorides/anhydrides for reaction with alcohols/amines (requires stringent anhydrous conditions; risk of polymer degradation).
  • –COOH → carbodiimide‑mediated esterification with alcohols (DMAP catalysts), though amide formation is more common.
  • Salt formation: Neutralization with bases (Na+, K+, TEA) increases aqueous solubility and can modulate reactivity.

• Macromolecular synthesis roles

  • As a 4‑point crosslinking node, it constructs networks with polyamines, enabling tunable gelation kinetics and mechanical properties.
  • As a soluble scaffold, it presents four handles to assemble multivalent displays (e.g., peptides, haptens) with controlled spacing.
  • As a phase‑transferable carrier, PEG’s amphiphilicity can solubilize hydrophobic motifs once conjugated.

• Retrosynthetic value

  • Replaces small‑molecule tetracarboxylic acids where high water compatibility, reduced immunogenic adsorption, and flexible linkers are desired.

• Workup/purification

  • Dialysis, ultrafiltration, and anti‑solvent precipitation effectively remove small‑molecule reagents and byproducts, avoiding silica chromatography.

Target Specificity

Not applicable. This product is a synthetic polymer reagent and does not have antigen/epitope targets, clone IDs, or species reactivity. No target specificity information is provided in the Product Data.