HS-PEG24-CH2CH2COOH , CAS No.H1444782

CAS: H1444782 Cat. No.: H1444782 Formula: C₅₁H₁₀₂O₂₆S Molecular Weight: 1163.40

Storage

Store at -20°C

Shipped In

Ice chest + Ice pads

Overview

HS-PEG24-CH2CH2COOH is a PEG-based PROTAC linker that can be used in the synthesis of PROTACs.

Specifications

Storage

Store at -20°C

Shipped In

Ice chest + Ice pads

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

Names and Identifiers

Molecular Weight

1163.40

Application Protocols

No antibody/assay validation protocols are provided for this item. For laboratory use, typical workflows include:

• EDC/NHS coupling of the carboxyl terminus to amine-bearing targets (e.g., proteins, surfaces), and
• Thiol conjugation to maleimide-functional species or self-assembly on gold surfaces.

Protocol specifics (concentrations, times, buffers) should be developed and optimized per application. Refer to the Reaction Conditions tab for general literature guidance.

Biological Roles

HS-PEG24-CH2CH2COOH is a synthetic, non-biological linker. It does not have intrinsic metabolic or signaling roles, but it is widely used to modulate biological interfaces and macromolecules (literature/general):

• PEGylation effects:
  • Increases hydrophilicity and hydration shell around biomolecules or particles, reducing nonspecific protein adsorption and aggregation.
  • Can extend in-solution stability of proteins/enzymes by steric shielding when covalently attached (formulation context), without implying therapeutic benefit.
• Surface biology:
  • Formation of PEGylated self-assembled monolayers on gold or other thiol-reactive surfaces yields antifouling coatings that resist biofouling and cell adhesion.
  • Terminal –COOH provides a handle to present bioactive ligands (via amide formation) at controlled densities on surfaces or nanoparticles.
• Bioconjugation orthogonality:
  • Thiol selectivity toward maleimides and gold allows site-specific attachment, while carboxyl group can be coupled to amines, supporting two-point attachments or oriented immobilization.

Note: While PEG linkers influence biomolecular behavior and surface interactions, any biological performance depends on the conjugation partner and system design. This product is for research use only and is not intended for diagnostic or therapeutic applications.

Buffer Applications

This product is not a pH buffer; however, successful use in bioconjugation depends on appropriate buffer selection (literature/general guidance):

• EDC/NHS-mediated activation of –COOH:
  • Activation buffer: MES (0.05–0.1 M), pH 5.0–6.0; low ionic strength favors activation and reduces hydrolysis.
  • Coupling buffer: Phosphate or HEPES, pH 7.2–7.8; avoid primary amine buffers (e.g., Tris) during activation as they quench activated esters.
  • Additives: 0.1–0.5 M NaCl can reduce electrostatic artifacts on charged surfaces.
• Thiol–maleimide coupling:
  • Preferred buffers: Phosphate or HEPES, pH 6.5–7.5; maintain slightly acidic to neutral pH to favor thiolate formation without excessive maleimide hydrolysis.
  • Reducing conditions: Use TCEP (0.2–1 mM) rather than DTT/βME to avoid competing thiols in coupling products; degas buffers to limit oxidation.
• Gold SAM formation:
  • Solvent/buffer: Ethanol or ethanol/water mixtures; aqueous buffers (pH 6–8) also used after initial assembly for ligand presentation.

All concentrations and timings should be optimized empirically for the specific substrate and conjugation partner.

Green Alternatives

Although HS-PEG24-CH2CH2COOH is a specialty linker rather than a solvent, greener choices can be made around its use—particularly in coupling reagents, catalysts, and solvent systems.

• Greener coupling strategies (literature/general):
  • Prefer water-based carbodiimide chemistry (EDC·HCl) with NHS or sulfo-NHS over DCC/HOBt in organic solvents; avoids urea precipitates and minimizes explosive/acute hazards associated with HOBt.
  • Enzymatic or organocatalytic amidations (where compatible) can reduce reliance on hazardous reagents, though scope may be narrower.
• Solvent considerations:
  • Use water or water/ethanol mixtures when forming SAMs or performing bioconjugations; minimize DMF/ACN usage where possible.
  • Replace DMF with safer alternatives (e.g., Cyrene, propylene carbonate) when solubility and reaction compatibility allow; validate on small scale first.
• Process improvements:
  • Employ micro-scale, high-concentration conditions to reduce solvent volumes.
  • Implement in-line desalting or aqueous-phase workups to decrease organic waste.

Comparison (general):

• DCC/HOBt (legacy) vs EDC/NHS (greener):
  • Hazard: HOBt is energetic; EDC/NHS is less hazardous.
  • Medium: DCC/HOBt typically requires anhydrous organic; EDC/NHS can proceed in water.
  • Byproducts: DCC generates DCU (insoluble waste); EDC gives water-soluble ureas.

Pharmaceutical Uses

No therapeutic or clinical claims are made for this reagent. In pharmaceutical research and manufacturing contexts (general/literature):

• Excipient/linker roles:
  • Used as a PEGylated linker to attach ligands, peptides, or polymers to surfaces (e.g., nanoparticles, medical device prototypes) in R&D settings to study colloidal stability and surface interactions.
  • Facilitates insertion of hydrophilic spacers between actives and solid supports to tune spacing and reduce steric hindrance in assay components.
• Process considerations:
  • Preference for water-based EDC/NHS chemistry enables cleaner processes and easier removal of byproducts.
  • Analytical release may include identity (NMR, MS), functionality assays (Ellman’s for –SH, titration for –COOH), residual solvent analysis, and bioburden/endotoxin testing if used in proximity to biologicals (as applicable to internal specifications).
• Regulatory notes:
  • PEGs are common in pharmacopeial monographs, but heterobifunctional PEG linkers like HS-PEG24-CH2CH2COOH are typically custom/novel and may not have compendial status. Lot-specific CoA defines quality attributes for research use.

For any use beyond research, additional qualification and validation are required per internal quality systems and regulatory frameworks.

Physical Properties

• Appearance: Not specified for this item; refer to CoA/Spec Sheet.
• Molecular Weight: Not specified for this item; refer to CoA/Spec Sheet. (Literature note: a PEG24 backbone contributes roughly 24 × 44 Da ≈ 1056 Da prior to end-groups; actual MW depends on precise structure and end-group mass and should be verified on CoA.)
• Molecular Formula: Not specified for this item; refer to CoA/Spec Sheet.
• Melting point / boiling point: Not specified for this item; refer to CoA/Spec Sheet. (General: PEG oligomers often show glass transitions or broad softening rather than sharp MPs.)
• Density, refractive index, pKa, logP: Not specified for this item; refer to CoA/Spec Sheet.
• Solubility (literature/general):
  • Typically highly soluble in water and polar organic solvents (e.g., methanol, ethanol, acetonitrile, DMSO, DMF); limited solubility in nonpolar solvents due to PEG polarity.
  • Carboxy terminus enhances aqueous solubility in basic media (as the carboxylate); thiol end-group has minimal impact on bulk solubility but is oxidation-sensitive.
• Hygroscopicity (general): PEG oligomers can be hygroscopic and absorb moisture; equilibrate in a desiccator prior to weighing for analytical accuracy.

All numerical specifications and certificate-backed values must be taken from the item’s CoA/Spec Sheet.

Quality & Grades

• Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.
• What “heterobifunctional PEG” quality typically implies (general):
  • Functionality fidelity: High end-group integrity (free –SH, free –COOH) with low levels of hydrolyzed, capped, or oxidized termini.
  • Narrow oligomer distribution: Controlled PEG length (here, nominal “24” repeat units). PEGs are often polydisperse; reporting may include average Mn and PDI by GPC.
  • Residual solvent/reagent control: Low residuals from activation, protecting groups, or coupling reagents (documented on CoA when applicable).
  • Analytical confirmation: 1H/13C NMR, MALDI-TOF/ESI-MS (for oligomers), FTIR for end-group bands, and possibly titration for acid value or Ellman’s assay for free thiol content.
• Stabilizers/additives: Not specified for this item; refer to CoA/Spec Sheet. (General: Thiol-PEGs are sometimes supplied under inert gas or with minimal headspace to limit oxidation; no stabilizers are preferred when downstream bioconjugation is intended.)
• Practical implications:
  • If high-performance bioconjugation is critical, verify free-thiol percentage and acid number on the lot-specific CoA.
  • For surface assembly on metals (e.g., Au), trace metal content may matter; consult CoA if relevant.

Reaction & Applications

This reagent is designed as a modular linker for bioconjugation, materials surface modification, and nanotechnology, leveraging orthogonal reactivity of the thiol and carboxylic acid termini.

• Representative application families (literature/general):
  • Carbodiimide-mediated amide formation: Activate –COOH with EDC (± NHS) to couple to primary amines on proteins, peptides, polymers, or surfaces.
  • Thiol–maleimide coupling: Attach the thiol terminus to maleimide-bearing cargos (or vice versa) under near-neutral pH with rapid kinetics and high selectivity.
  • Gold surface functionalization: Form self-assembled monolayers (SAMs) on Au via the thiol, presenting a terminal –(CH2)2–COOH for further derivatization or antifouling PEG layer formation.
  • Disulfide chemistry: Optional reversible linkages via controlled oxidation to disulfide bridges; reduce back with TCEP/DTT as needed.
  • Polyester/amide synthesis: Use –COOH to prepare PEGylated esters or amides, introducing hydrophilicity and stealth in polymeric materials.
• Practical tips:
  • Maintain the thiol in reduced form: Work under inert atmosphere; include TCEP (0.2–1 mM) in buffers if compatible; avoid copper/iron contaminants.
  • For EDC/NHS couplings: Pre-activate at pH 5.0–6.0 (MES), then couple at pH 7.2–7.8; exclude primary amines from activation buffer.
  • For SAMs on gold: Clean substrate, use 0.1–1 mM solutions in EtOH or EtOH/H2O, incubate 2–24 h, and rinse thoroughly.

These applications reflect common literature practices for thiol/carboxyl-terminated PEG linkers and should be tailored to the end-use system.

Reaction Conditions

General literature guidance for typical transformations involving HS-PEG24-CH2CH2COOH (optimize per system):

• EDC/NHS-mediated amide formation (–COOH to amine):
  • Activation: Dissolve linker (1–10 mM) in MES buffer (0.05–0.1 M, pH 5.0–6.0); add EDC (1–2 equiv) and NHS or sulfo-NHS (1–5 equiv); stir 10–30 min at RT.
  • Coupling: Add activated solution to amine-containing target in phosphate buffer (pH 7.2–7.8); react 1–4 h at RT. Quench residual active ester with Tris or ethanolamine.
• Thiol–maleimide coupling (thiol end to maleimide):
  • Conditions: Phosphate or HEPES buffer, pH 6.5–7.5; 0.5–2 h at RT; exclude competing thiols. Maintain thiol in reduced form with TCEP (0.2–1 mM).
• Thiol self-assembled monolayers (SAMs) on gold:
  • Conditions: 0.1–1 mM in ethanol or 70:30 EtOH/H2O; incubate cleaned Au substrates 2–24 h at RT; rinse with solvent and water; optional backfilling with short alkanethiols.
• Thiol–ene click to acrylates (materials):
  • Conditions: Solvent-free or in EtOH/ACN; photoinitiator (e.g., DMPA); UV 320–365 nm; minutes to tens of minutes exposure; inert atmosphere improves outcome.

Expected yields and kinetics depend strongly on partners and stoichiometry; monitor by MS, HPLC, or surface-sensitive techniques (SPR, XPS, contact angle) as appropriate.

Safety & Handling

• GHS classification, pictograms, signal word, H-statements: Not specified for this item; refer to the SDS for authoritative safety information.
• Anticipated hazards (general for thiol/carboxyl PEGs):
  • Low volatility; low acute toxicity is typical for PEG oligomers, but avoid inhalation of dusts/aerosols and contact with eyes/skin.
  • Thiol end-group can oxidize to disulfides; thiols may have strong odor and can cause irritation/sensitization in some individuals.
  • Carboxylic acid may cause mild skin/eye irritation; neutralization generates heat and salts.
• Incompatibilities (general):
  • Strong oxidizers (can over-oxidize thiols and degrade polyethers);
  • Strong bases/acids during prolonged exposure (hydrolysis/ether cleavage under harsh conditions);
  • Transition-metal salts that catalyze thiol oxidation.
• Safe handling/PPE:
  • Wear lab coat, safety glasses, and nitrile gloves; handle powders/lyophilizates in a fume hood to minimize dust exposure.
  • Use inert atmosphere (N2/Ar) or add a mild, metal-free reducing agent (e.g., TCEP) for workflows requiring free thiol.
• First-aid (overview; consult SDS):
  • Skin/eye contact: Rinse with water for several minutes; remove contaminated clothing; seek medical attention if irritation persists.
  • Ingestion/inhalation: Move to fresh air; rinse mouth; obtain medical advice as needed.
• Fire & thermal decomposition (general): Combustible organic polymer; use water spray, CO2, or dry chemical. Decomposition may produce CO/CO2 and sulfur-containing vapors.

Always consult the product SDS for definitive hazard and response guidance.

Solvent Selection

This heterobifunctional PEG is highly polar and generally water-miscible; solvent choice should prioritize maintaining functionality (thiol reduced; carboxyl unhydrolyzed) and compatibility with the coupling chemistry.

• Polarity/miscibility (literature/general):
  • Typically miscible with water and polar organics (MeOH, EtOH, ACN, DMSO, DMF). Limited solubility in nonpolar solvents (hexanes, toluene) due to PEG polarity.
• Choosing solvents by application:
  • EDC/NHS activation of the carboxyl terminus: Aqueous buffer (e.g., MES, pH 5–6) or mixed aqueous/organic systems to improve solubility while minimizing hydrolysis.
  • Amide coupling to amines on biomolecules/surfaces: Perform in PBS or phosphate buffer at pH 7.2–7.8 after in situ NHS ester generation; add 5–20% DMF/DMSO if needed for solubility.
  • Thiol–maleimide conjugation: pH 6.5–7.5 in phosphate or HEPES buffer; minimize organic cosolvents that slow maleimide kinetics.
  • Thiol self-assembly on gold: Ethanol, isopropanol, or water/ethanol mixtures; degas solvents to limit oxidation.
• Practical notes:
  • Avoid amine-containing buffers during carbodiimide activation (they quench activated esters).
  • Use oxygen-reduced solvents or add TCEP when free thiol must be preserved.

Comparison (general):

• DMSO vs DMF: DMSO offers superior biocompatibility and lower volatility; DMF may better solubilize some hydrophobic cargos but is more regulated in GMP settings.

Storage & Reconstitution

• Storage conditions (item-specific): Store at -20°C. Shipped in ice chest with ice pads. Minimize freeze–thaw cycles.
• Container and atmosphere (general best practice): Keep tightly closed under dry, inert gas (N2/Ar) to limit moisture uptake and thiol oxidation. Store desiccated and protected from light.
• Stability considerations (general): Thiol end-groups can oxidize to disulfides during storage, especially with air/moisture exposure. If oxidation is detected, reduce with TCEP immediately before use if a free thiol is required.
• Reconstitution (general guidance):
  • Solvents: Water, PBS, MES, or polar organics (DMSO, DMF, ethanol) depending on application; start at 1–10 mg/mL and adjust as needed.
  • Degas solutions to limit oxidation; prepare fresh working solutions.
  • For bioconjugation, pre-filter (0.22 µm) if particulate matter is present; avoid amine-containing buffers during carbodiimide activation.
• Aliquoting: Prepare single-use aliquots to avoid repeated thawing and moisture ingress. Label with preparation date and solvent.
• Specifications: Any product-specific stabilizers, exact solubility limits, and solution stability are Not specified for this item; refer to CoA/Spec Sheet.

Research Use Only: Not for human or veterinary use.

Structure & Identity

HS-PEG24-CH2CH2COOH is a heterobifunctional polyethylene glycol (PEG) linker bearing a terminal thiol (–SH) on one end and a carboxylic acid (–CH2CH2–COOH) on the other, separated by a spacer of 24 ethylene glycol repeat units.

• Item-specific identifiers
  • CAS: Not specified for this item; refer to CoA/Spec Sheet.
  • InChIKey: Not specified for this item; refer to CoA/Spec Sheet.
  • SMILES: 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.
• Structural features (general description)
  • Backbone: Linear PEG consisting of 24 –CH2–CH2–O– units (literature/typical for “PEG24”).
  • End-groups: One terminus is a free thiol (–SH); the opposite terminus is an aliphatic carboxylic acid preceded by a two-methylene spacer (–CH2–CH2–COOH).
  • Functional group chemistry: Thiol is nucleophilic and redox-active (forms disulfides); carboxylate can be activated for amide/ester formation.
  • 2D description in words: A flexible, hydrophilic polyether chain with an –SH group at one end and –O–(CH2CH2O)24–CH2–CH2–COOH terminating motif at the other (schematic/literature description).
• Stereochemistry and rings: None; acyclic, achiral polyether chain (general).

Note: Exact sequence/connectivity notation and analytical identity parameters should be confirmed against the item’s CoA/Spec Sheet for this specific lot.

Synthetic Utility

As a heterobifunctional PEG, HS-PEG24-CH2CH2COOH provides orthogonal handles for stepwise assembly of complex constructs (literature/general):

• Key functional groups and reactivity:
  • Thiol (–SH): Nucleophile for michael additions (e.g., to maleimides, acrylates), thiol–ene/thiol–yne photochemistry, and Au–S bond formation on gold surfaces.
  • Carboxylic acid (–COOH): Precursor to activated esters (NHS), acyl azides, or acid chlorides; couples to amines to yield amides; to alcohols to form esters.
  • PEG backbone: Provides water solubility/flexibility; acts as a spacer to reduce steric hindrance and modulate distance/orientation between conjugation partners.
• Named/representative transformations:
  • EDC/NHS amide coupling to amine-bearing biomolecules or surfaces.
  • Thiol–maleimide conjugation for site-specific labeling of cysteine residues or maleimide-functional materials.
  • Photoinitiated thiol–ene addition to acrylate-functional polymers/coatings under UV or radical conditions.
  • SAM formation on gold for biosensor platforms with terminal carboxyl presentation.
• Retrosynthetic perspective:
  • Serves as a modular spacer between a thiol-addressable substrate (metal, maleimide tag) and an amine-bearing payload; or conversely, as a carboxyl-addressable handle leaving thiol free for subsequent coupling.

This utility enables construction of PEGylated conjugates, surfaces, and nanomaterials with controlled spacing and improved hydrophilicity.

Target Specificity

Not applicable. This product is a synthetic chemical linker, not an antibody or affinity reagent. No antigen/epitope, clone, isotype, or species reactivity information applies.