≥98% for sensitive chromatographic and analytical workflows requiring minimal baseline interference.
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Storage & shipping
Store at -20°C Ships Ice chest + Ice pads Check lot-specific COA for exact specifications.
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Quality documents
SDS, COA, datasheet, and spec sheet available for download. Lot-specific COA accessible via lot number lookup.
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Literature proof
Cited in 0 peer-reviewed publications across chromatography, organic synthesis, and cross-coupling reactions.
Overview
m-PEG6-CH2COOH is a PEG derivative containing a terminal carboxylic acid. The terminal carboxylic acid can be reacted with primary amine groups in the presence of activators (e.g. EDC, or DCC) to form a stable amide bond. The hydrophilic PEG spacer increases solubility in aqueous media.
This compound belongs to the class of organic compounds known as carboxylic acids. These are compounds containing a carboxylic acid group with the formula -C(=O)OH.
External Descriptors
Not available
1. Djoumbou Feunang Y, Eisner R, Knox C, Chepelev L, Hastings J, Owen G, Fahy E, Steinbeck C, Subramanian S, Bolton E, Greiner R, and Wishart DS. ClassyFire: Automated Chemical Classification With A Comprehensive, Computable Taxonomy. Journal of Cheminformatics, 2016, 8:61.
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Application Protocols
Representative research protocol (literature/general) for preparing NHS-activated m-PEG6-CH2COOH and coupling to an amine-functionalized surface:
A. NHS activation (aqueous):
Dissolve m-PEG6-CH2COOH at 5–20 mM in 50 mM MES buffer, pH 5.5.
Add NHS (1.2 equiv) and EDC·HCl (1.2–1.5 equiv). Mix gently 15–20 min at room temperature.
Use immediately for coupling to minimize hydrolysis of the NHS ester.
B. Coupling to amine surface (e.g., aminated silica or polymer):
Rinse surface with coupling buffer (PBS or 50 mM phosphate, pH 7.8–8.2).
Add the activated PEG solution; incubate 1–2 h at room temperature with gentle agitation.
Rinse thoroughly with buffer, then quench residual active esters with 50 mM ethanolamine or 50 mM Tris, pH 8.5, for 15–30 min.
Rinse and dry as required.
Notes:
Avoid amine-containing buffers (e.g., Tris) during activation steps.
For protein conjugation, perform activation in MES (pH ~5.5), then transfer to the protein solution buffered at pH 7.4–8.0; keep protein concentrations modest to limit viscosity.
For poorly wetting substrates, add 5–20% v/v ethanol or acetonitrile as a co-solvent if compatible.
These are general guidelines. Optimize stoichiometry, pH, and time for your specific substrate and performance requirements.
Biological Roles
This product is a synthetic PEG linker and does not have intrinsic biological activity. However, PEG chains are widely used in biochemistry and materials biology for their physicochemical attributes (literature/general):
PEG as an inert spacer: Provides hydrophilic, flexible separation between a biomolecule/nanomaterial and a conjugated ligand, reducing steric hindrance and nonspecific interactions.
Protein-resistance: PEGylated surfaces resist protein adsorption and cell adhesion, improving antifouling properties in biosensors and microfluidic devices.
Solubility enhancement: Conjugation with short PEG chains (e.g., PEG6) can improve aqueous solubility and reduce aggregation of hydrophobic ligands or nanoparticles.
Reduced immunogenicity: While commonly noted for larger PEGs in therapeutic contexts, short PEGs can also mitigate recognition in research formulations; no clinical claims are made here.
Acid functionality: The terminal –CH2–COOH allows site-selective coupling to amines on peptides/proteins or to amine-functionalized materials under mild aqueous conditions.
Note: Use is limited to research applications. Effects in biological systems depend entirely on the conjugation partner and architecture; no pharmacological or clinical properties are implied for this item.
Buffer Applications
Although not a buffer itself, m-PEG6-CH2COOH is frequently used in buffers for carbodiimide-mediated coupling (literature/general):
EDC/NHS activation buffer:
MES buffer, 50–100 mM, pH 4.7–6.0 to favor O-acylisourea/NHS ester formation.
Typical workflow: dissolve m-PEG6-CH2COOH in water or aqueous MES; add equimolar NHS (or sulfo-NHS) and 1–2 equiv EDC; react 10–30 min at room temperature.
Coupling buffer:
Phosphate or HEPES, pH 7.4–8.5 for reaction with primary amines on biomolecules or amine-coated surfaces.
Include 0.1–0.5 M NaCl when coupling to proteins to minimize electrostatic aggregation, as needed.
Quenching and cleanup:
Quench residual activated esters with Tris or ethanolamine after coupling.
Desalt via spin columns, dialysis, or SEC to remove small-molecule reagents.
Practical notes:
Avoid Tris or other amine-containing buffers during activation (they compete with coupling).
Prepare activation solutions fresh; NHS esters hydrolyze with half-lives ranging from minutes to hours depending on pH and temperature.
For poorly soluble substrates, perform activation in minimal dry DMF/DMSO, then dilute into MES immediately prior to contacting the amine-bearing target.
Green Alternatives
Greenness considerations for m-PEG6-CH2COOH focus on solvent and coupling reagent choices rather than the linker itself, which is a relatively benign, non-volatile polyether.
Greener solvent strategies (literature/general):
Prefer water or aqueous buffers (e.g., MES) for EDC/sulfo-NHS couplings when the substrate permits.
Replace DMF/NMP with safer polar aprotics like Cyrene or propylene carbonate for activation steps where compatible.
Use ethanol or isopropanol co-solvents instead of acetonitrile where solubility allows.
Coupling reagent alternatives:
Water-soluble carbodiimide (EDC) with sulfo-NHS is preferable to DCC (which generates insoluble urea waste and sensitizers).
Enzymatic ligations (e.g., microbial transglutaminase for protein substrates) can avoid chemical activators if compatible, though not universally applicable.
Workup and waste minimization:
Conduct reactions at higher concentrations to reduce solvent volumes; recover and recycle aqueous phases where feasible.
Avoid halogenated solvents; if DCM is required for downstream steps, consider ethyl acetate as a substitute.
Greener: Aqueous MES + EDC/sulfo-NHS → reduced volatility/toxicity, simpler aqueous waste handling.
Trade-offs: Greener solvents may reduce solubility of hydrophobic substrates, requiring co-solvents or biphasic methods; EDC routes can give more hydrolysis, necessitating prompt workup.
Pharmaceutical Uses
For research and development only. No clinical or therapeutic claims are made.
Role in formulation research (literature/general):
PEGylation handle: serves as a hydrophilic spacer with a carboxylate terminus for conjugating to amine-bearing excipients, peptides, or polymers to tune solubility, stability, and viscosity in pre-formulation studies.
Surface engineering: used to end-functionalize nanoparticles (e.g., silica, metal oxides after amination) to reduce nonspecific interactions and modulate zeta potential.
Prototyping linkers: short PEG linkers help map structure–property relationships (e.g., PEG length vs. aggregation) before scaling to longer PEGs.
Regulatory status:
No pharmacopeial grade is specified for this item; consult the CoA/Spec Sheet for quality attributes if considering regulated pathways in the future.
Process considerations:
Residual coupling reagents and urea byproducts must be removed via dialysis, SEC, or ultrafiltration in formulation research.
Short PEGs are typically easier to analyze by LC–MS/NMR than high-MW PEGs, aiding characterization.
Note: Use is limited to laboratory research. Suitability for any GMP or clinical application requires additional qualification not provided here.
Physical Properties
m-PEG6-CH2COOH is a low–molecular-weight, monodisperse PEG derivative. As a short PEG chain, it is typically a low-melting solid or viscous wax and is highly hydrophilic.
From Product Data:
Appearance: Not specified for this item; refer to CoA/Spec Sheet.
Storage/Shipping (item-specific):
Store at −20 °C.
Shipped on ice (ice chest + ice pads).
Literature/general expectations (non-spec, for context):
Aggregation state: often a white to off-white waxy solid at ambient temperature for PEG6 derivatives.
Solubility: freely soluble in water and polar protic solvents (e.g., methanol, ethanol) and many polar aprotic solvents (e.g., DMSO, DMF, acetonitrile); limited solubility in nonpolar hydrocarbons (literature).
pKa: terminal carboxylic acid expected in the typical range ~4–5 (literature).
Hygroscopicity: PEG chains are hygroscopic and can absorb atmospheric moisture (general behavior).
Partitioning: strongly hydrophilic; logP expected to be very low/negative (literature).
Viscosity: solutions can be moderately viscous at high concentrations due to PEG hydration (general).
Note: No item-specific numerical specifications (mp, bp, density, refractive index, UV cutoff, residuals) are provided here; consult the CoA/Spec Sheet for definitive values if required for regulated use.
Quality & Grades
From Product Data:
Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.
Interpretation and guidance (general):
PEG linkers are frequently offered as monodisperse (discrete length) materials prepared from oligomeric hexaethylene glycol, distinct from polydisperse mPEG polymers. If “monodisperse” or “>95%” purity is specified on the CoA, it typically refers to a single oligomer length verified by LC/MS and NMR.
For conjugation applications, low levels of hydrolytic impurities (e.g., residual alcohol end-groups), residual solvents, and inorganic salts are important. HPLC or LC–MS purity specifications indicate suitability for bioconjugation and materials surface chemistry.
Stabilizers: PEG-based acids usually do not require stabilizers; absence/presence of stabilizers should be confirmed on the CoA if critical to your workflow.
Documentation: If you require trace analysis (metals, water content, residual solvents), request the product CoA/Spec Sheet for lot-specific details. Do not assume equivalence to bulk PEG grades (USP/NF or industrial) unless explicitly stated.
Reaction & Applications
This reagent is a monofunctional PEG linker for attaching a short, hydrophilic spacer terminated in a carboxylic acid to molecules, polymers, or surfaces.
Key application families (literature/general):
Amide coupling to primary amines: Using EDC or DIC with NHS or sulfo-NHS to generate an active ester, followed by reaction with amines on small molecules, peptides, proteins, or amine-functionalized surfaces. The methoxy cap prevents undesired crosslinking.
Ester formation: Activation of the carboxyl group (e.g., via DCC/DMAP, CDI) to form esters with alcohol-bearing substrates when amide linkages are not desired.
Surface modification: Grafting onto amine-rich polymer films (e.g., PEI-coated particles), silica or metal oxides prefunctionalized with amines, yielding hydrophilic, protein-resistant coatings and controlled spacing of functional groups in materials science.
Spacer in conjugation: The PEG6 chain improves water solubility, reduces aggregation, and provides steric spacing between a core scaffold and a terminal acid-derived linkage, benefiting bioconjugation and nanomaterial interfaces.
Click sequence integration: The carboxyl can be converted to NHS ester, hydrazide, or hydroxamate handles for subsequent orthogonal reactions.
Practical notes:
Maintain pH 4.7–6.0 during EDC/NHS activation to maximize O-acylisourea formation and minimize hydrolysis; perform amine coupling at pH 7.5–8.5.
Use freshly prepared solutions; activated esters hydrolyze in water.
For poorly soluble targets, carry out activation in dry DMF/DMSO, then introduce to buffered aqueous reaction.
Reaction Conditions
General, literature-based guidance for common transformations of m-PEG6-CH2COOH. These are typical ranges; optimize per substrate.
EDC/NHS amide coupling (aqueous):
Solvent: 50–100 mM MES, pH 4.7–6.0 for activation; couple to amines at pH 7.5–8.5 (phosphate/HEPES).
Temperature/time: 20–25 °C; activation 10–30 min; coupling 0.5–4 h. Hydrolysis competes at higher pH; work promptly.
Amide coupling (organic):
Solvent: anhydrous DMF, DCM, or MeCN; base: DIPEA or TEA.
Reagents: HATU or TBTU (1.1–1.5 equiv) with 1.5–3.0 equiv amine. 0–25 °C, 0.5–2 h to completion (literature typical).
Esterification:
DCC (1.1–1.5 equiv) + DMAP (0.05–0.1 equiv) in DCM/DMF; 0–25 °C, 2–16 h. Filter off dicyclohexylurea.
Alternatively, CDI activation in acetonitrile/DMF; then add alcohol and base.
Acid chloride route:
SOCl2 (3–5 equiv) with catalytic DMF, anhydrous DCM; reflux 0.5–2 h; remove excess reagent, then add amine/alcohol at 0–25 °C. Protect from moisture.
Analytics and QC:
Monitor by LC–MS (PEG adducts often show sodium/potassium adducts). NMR in CD3OD or DMSO-d6; disappearance of carboxylic acid OH and appearance of amide/ester signals confirm conversion.
Safety & Handling
PEGylated carboxylic acids are generally considered to be of low acute hazard, but handle as a laboratory chemical.
From Product Data:
GHS classification / Pictograms / Signal word / H-statements: Not specified for this item; refer to SDS.
Storage: Store at −20 °C. Shipments are cooled (ice chest + ice pads).
General laboratory precautions (literature/general):
PPE: wear lab coat, safety glasses, and suitable gloves (e.g., nitrile). Avoid inhalation of dust/aerosols and contact with eyes/skin.
Handling: Work in a clean, dry environment. PEG derivatives can be hygroscopic; keep containers tightly closed. Minimize prolonged exposure to ambient humidity.
Incompatibilities: Strong oxidizing agents may degrade polyethers; strong bases can form carboxylate salts and may promote PEG chain cleavage under harsh conditions; dehydrating agents may esterify/condense the acid (general chemical reactivity).
First aid overview: If inhaled, move to fresh air. For skin/eye contact, rinse with water for several minutes; remove contaminated clothing. If ingested, rinse mouth with water. Seek medical attention as appropriate. Defer to SDS for authoritative guidance.
Thermal decomposition: Polyethers can form aldehydes/organic acids upon overheating; avoid thermal abuse.
Always consult the product-specific SDS before use for definitive hazard and response information.
Solvent Selection
m-PEG6-CH2COOH is a highly polar, hydrogen-bonding solute with excellent aqueous compatibility.
Polarity and miscibility (literature/general):
Water: highly soluble; forms clear solutions across a broad concentration range.
Carbodiimide (EDC/NHS) activation: use mildly acidic aqueous buffers (e.g., MES, pH 4.7–6.0) or mixed aqueous/DMF systems for hydrophobic substrates.
Esterification with alcohols: dry polar aprotic solvents (e.g., DMF, DCM with coupling reagents) can be advantageous.
Surface modification (oxide surfaces, polymers): water, alcohols, or mixed solvent systems improve wetting and uniform coverage.
Practical tips:
For water-sensitive couplings, prepare stock solutions in anhydrous DMF or DMSO and add to aqueous buffers immediately prior to activation.
Viscosity increases with concentration; adjust pipetting speeds and use wide-bore tips if needed.
Small comparison (literature/general):
PEG6-COOH vs PEG3-COOH: PEG6 offers longer hydrophilic spacing and greater aqueous solubility for steric shielding.
PEG6-COOH vs PEG12-COOH: PEG12 provides greater spacing but at higher viscosity and potential for increased chain entanglement.
Storage & Reconstitution
From Product Data:
Storage Conditions: Store at −20 °C.
Shipped In: Ice chest + ice pads.
General handling (literature/general):
Hygroscopic: minimize exposure to ambient humidity. Allow vial to equilibrate to room temperature in a desiccator before opening to prevent moisture condensation.
Reseal promptly under dry air or nitrogen. Consider storing with desiccant.
Aliquoting: If frequent use is anticipated, prepare small aliquots to avoid repeated freeze–thaw/moisture cycling.
Reconstitution guidance:
Aqueous use: dissolve directly in deionized water or buffer (e.g., MES, phosphate). Gentle warming (25–30 °C) and vortexing may help.
Organic use: readily dissolves in DMSO or DMF; for strictly anhydrous reactions, use dry solvents and handle under inert atmosphere.
Typical working concentrations: 1–100 mM depending on application (optimize per protocol).
Stability:
Store solutions refrigerated (4 °C) for short-term use (hours to a few days). For longer-term storage, prepare single-use aliquots and freeze at −20 °C to −80 °C. Avoid repeated freeze–thaw cycles.
Avoid prolonged exposure to strong acids/bases and elevated temperatures, which can promote PEG degradation or carboxylate hydrolysis.
For definitive shelf-life, impurity limits, and solution stability, consult the lot-specific CoA/Spec Sheet.
Structure & Identity
Monofunctional PEG linker bearing a terminal carboxymethyl group and a methoxy cap. Common structural shorthand: MeO–(CH2CH2O)6–CH2–COOH.
Structural features: one terminus is a methyl ether (–OCH3), the other terminus is a carboxymethyl (–O–CH2–COOH) attached through an ether to a hexaethylene glycol chain (six –CH2–CH2–O– repeats).
2D description: a linear polyether chain of six ethylene glycol units; the left end is capped by a methoxy substituent; the right end continues via an ether oxygen to a methylene, then a carboxylic acid. No rings or stereocenters.
Not specified for this item; refer to CoA/Spec Sheet: Molecular formula, Molecular weight, SMILES.
Synthetic Utility
Functional group set and reactivity (literature/general):
Terminal carboxylic acid (–CH2–COOH):
Forms amides with primary/secondary amines (EDC/NHS, HATU, DIC/Oxyma).
Converts to acid chlorides (e.g., with oxalyl chloride or SOCl2) to access esters/amides rapidly (moisture-sensitive route).
Activates to NHS/sulfo-NHS esters, hydrazides, or hydroxamates.
Polyether backbone (PEG6):
Confers hydrophilicity and flexibility; largely inert toward many reaction conditions, but avoid strong acids/bases and oxidants over extended times to prevent cleavage or oxidation.
Methoxy cap:
Blocks the second terminus, preventing crosslinking and ensuring monofunctional behavior.
Applications:
Spacer installation on complex molecules to improve solubility or reduce steric crowding near binding motifs.
Surface and polymer modification: coupling onto amine-functionalized resins, membranes, nanoparticles to create antifouling, hydrophilic interfaces.
Precursor for orthogonal handles: the acid can be transformed to azides, alkynes, or maleimides via short synthetic sequences (e.g., amide linkage to amino-azides), enabling click chemistry on a PEG6 spacer.
Practical tips:
For aqueous couplings, control pH stringently; for organic-phase activations, dry solvents and bases (e.g., DIPEA) improve conversions.
Characterization: LC–MS (ESI+/-), 1H/13C NMR in D2O, CD3OD, or DMSO-d6 are well-suited; watch for broad PEG resonances.
Target Specificity
Not applicable. This product is a small-molecule/oligomeric linker for materials and synthetic chemistry, not a biological targeting reagent such as an antibody or ligand with defined biochemical targets. For application-relevant information, refer to Reaction & Applications, Synthetic Utility, and Application Protocols.
Frequently Asked Questions
What is the purity of this product?
This product is supplied at ≥98% purity (chemical assay). Lot-specific values are stated on the Certificate of Analysis.
How should this product be stored?
Store at ?20 °C. Freezer storage is required to maintain the specified shelf life.
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 16142-03-3, the molecular formula is C13H26O8, and the molecular weight is 310.3 g/mol. InChIKey WJNNCBSSWKTIHI-UHFFFAOYSA-N.
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.
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