p-Ethynylphenylalanine - 10mM in DMSO , CAS No.278605-15-5

CAS: 278605-15-5 Cat. No.: P656480 Formula: C₁₁H₁₁NO₂ Peso molecolare: 189.21 PubChem CID: 25216972

GRADE & PURITY 10mM in DMSO

Storage

Store at -80°C

Shipped In

Dry ice packs + Cold packs

Panoramica

p-Ethynylphenylalanine (4-Ethynyl-L-phenylalanine) is a potent, selective, reversible and competitive inhibitor of tryptophan hydroxylase (TPH) , with a K i of 32.6 μM

In Vitro

p-Ethynylphenylalanine selectively and reversibly inhibits the biosynthesis of serotonin. p-Ethynylphenylalanine has a low affinity for various recombinant 5-HT receptors (5-HT 1 , 5-HT 2 , 5-HT 4 , 5-HT 5 , 5-HT 6 , and 5-HT 7 ). MCE has not independently confirmed the accuracy of these methods. They are for reference only.

In Vivo

p-Ethynylphenylalanine (30 mg/kg; i.p.) decreases in 5-HT and 5-HIAA levels in the rat midbrain but not in tissue . p-Ethynylphenylalanine does not inhibit the aromatic amino acid decarboxylase . MCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal Model: Male Sprague-Dawley rats (200 g) Dosage: 30 mg/kg Administration: Intraperitoneal injection Result: Decreased in 5-HT and 5-HIAA levels in the rat midbrain.

IC50& Target:Ki: 32.6 μM (TPH)

Specifications

Specifiche e purezza

10mM in DMSO

Meccanismi biochimici e fisiologici

p-Ethynylphenylalanine (4-Ethynyl-L-phenylalanine) is a potent, selective, reversible and competitive inhibitor of tryptophan hydroxylase (TPH) , with a K i of 32.6 μM.

Condizioni di conservazione di stoccaggio

Store at -80°C

Spedito in

Dry ice packs + Cold packs

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Nomi e identificatori

Isomeri SMILES

C#CC1=CC=C(C=C1)C[C@@H](C(=O)O)N

CAS alternativo

278605-15-5

PubChem CID

25216972

Termini MeSH

p-ethynylphenylalanine;pEPA cpd

Peso molecolare

189.21

Application Protocols

No item-specific, validated application protocols are provided in the Product Data. The following high-level, literature-based outlines are offered as general guidance; optimize for your system.

• Preparation of aqueous stock solution:

  • Dissolve the solid by adjusting to pH ~2–3 with dilute HCl or to pH ~9–10 with dilute NaOH; target 10–100 mM stock. Filter-sterilize (0.22 µm) if required. Store aliquots at −80°C.

• Protein labeling via CuAAC (after incorporation):

  1. Prepare protein (10–50 µM) in 50 mM phosphate or HEPES, pH 7.2.
  2. Add azide probe (50–500 µM), CuSO4 (100 µM), THPTA (200–500 µM), and sodium ascorbate (1–2 mM).
  3. React 30–60 min at RT with gentle mixing.
  4. Quench and remove copper/excess probe by gel filtration or dialysis.
  5. Verify labeling by LC–MS or in-gel fluorescence (if fluorogenic).

• SPPS incorporation (protected derivative required):

  • Use standard Fmoc protocols. Monitor for alkyne integrity by LC–MS. Avoid strong oxidants and prolonged UV exposure.

These outlines are for research use only and are not a substitute for detailed method development or the product SDS/CoA.

Biological Roles

General context (no clinical claims)

• p-Ethynylphenylalanine is a noncanonical analog of the essential amino acid phenylalanine. It is not a natural metabolite but can be incorporated into proteins using engineered aminoacyl-tRNA synthetase/tRNA pairs or via ribosomal synthesis in cell-free systems.

Functional roles in research (literature)

• Site-specific bioconjugation: The terminal alkyne serves as a bioorthogonal handle for CuAAC to append probes (fluorophores, affinity tags) to proteins and peptides, enabling imaging, pull-down assays, and interaction mapping.
• Structural biology: Strategic placement allows interrogation of local environments via the alkyne’s IR/Raman reporter band (in the cellular “silent” window), facilitating conformational studies without bulky labels.
• Chemical crosslinking and mapping: Post-expression click capture of interacting partners or ligands bearing azides can stabilize transient complexes for proteomic analysis.
• Proteostasis and folding studies: Replacement of Phe with this analog minimally perturbs hydrophobic packing relative to larger handles (e.g., strained alkynes), enabling nuanced examination of aromatic interactions.

Considerations

• Incorporation efficiency and fidelity depend on the engineered tRNA/synthetase system and expression host; optimization of induction, amino acid concentration, and media composition is required.
• The analog’s presence can modestly influence protein stability or function depending on residue context; experimental controls with wild-type proteins are recommended.
• For peptide work, SPPS incorporation is straightforward, with the alkyne surviving standard Fmoc chemistry; copper exposure should be minimized if the peptide will undergo sensitive downstream assays.

Buffer Applications

This compound is not a dedicated buffering reagent. As a neutral α-amino acid analog, its buffering capacity is limited to the generic acid–base pairs of the carboxylate and ammonium groups, which provide only weak buffering near their respective pKa values. For practical laboratory buffering, use established systems (e.g., phosphate pH 6–8, acetate pH 3.6–5.6, Tris pH 7–9) and incorporate p-ethynylphenylalanine as a solute or substrate as needed.

Practical notes

• To dissolve efficiently, adjust the solution pH away from the isoelectric point using dilute acid or base, then back-titrate to the desired buffer pH after complete dissolution.
• Maintain ionic strength with the chosen buffer to support bioconjugation reactions (e.g., 50–100 mM phosphate or HEPES). Avoid buffers that strongly chelate copper if performing CuAAC unless a suitable Cu(I) ligand is used to control speciation.

Green Alternatives

Context

• p-Ethynylphenylalanine is primarily used as a bioorthogonal handle. Greener considerations focus on the click chemistry modality, solvent choices, and metal usage rather than replacing the amino acid itself.

Greener strategies (literature-based)

• Cu-free click alternatives: Strain-promoted azide–alkyne cycloaddition (SPAAC) avoids copper, improving environmental and biological compatibility; however, it requires strained alkynes (not present here). For alkyne-bearing residues, consider using azide-functional residues (e.g., p-azido-phenylalanine) to leverage SPAAC on the partner.
• Photo-click and thiol–yne: Light-driven thiol–yne reactions can proceed without heavy metals; select photoinitiators and wavelengths compatible with the matrix and minimize solvent use.
• Aqueous media: Favor water or buffered aqueous/ethanol mixtures over dipolar aprotic solvents (DMF, DMSO) when feasible; maintain low organic cosolvent percentages.
• Ligand selection in CuAAC: Use water-soluble ligands (e.g., THPTA) to reduce copper loading and enable efficient reactions at ppm–low mol% levels, minimizing metal waste.

Comparison (qualitative)

• CuAAC with p-ethynylphenylalanine: High efficiency, small tags; involves copper and a reducing agent (ascorbate), typically in water.
• SPAAC with azido residues: Metal-free, biocompatible; requires bulkier strained alkyne partners and can be slower.

Trade-offs

• Retaining the terminal alkyne keeps molecular size minimal and maximizes synthetic flexibility; shifting to azide or strained systems may improve green metrics but can alter sterics, kinetics, and availability.

Pharmaceutical Uses

No pharmacopeial or excipient status is specified for this item; it is provided for research use only. The following reflects general, non-clinical laboratory practice.

Formulation and development contexts (general)

• Conjugation intermediate: Serves as an alkyne-bearing amino acid residue within peptides or proteins that are further functionalized via click chemistry to generate research-grade conjugates (e.g., fluorophore- or affinity-tagged constructs) for analytical or discovery workflows.
• Medicinal chemistry building block: Incorporated into peptide leads to adjust hydrophobic/aromatic interactions while providing a conjugation handle for SAR exploration; not intended for human or veterinary use.

Considerations

• Regulatory: Not intended for GMP manufacturing or clinical applications without further qualification. If translational work is planned, source protected derivatives qualified to appropriate standards and perform full impurity and metal analyses (e.g., residual Cu after CuAAC).
• Stability: Formulation should avoid prolonged high pH or elevated temperatures to limit racemization and side reactions at the alkyne.
• Process compatibility: For downstream analytics, removal of copper and excess azide/ligand after click steps (e.g., via dialysis, SEC, or chelating resins) is recommended to meet development-quality thresholds.

Physical Properties

Item-specific specifications

• Appearance: Not specified for this item; refer to CoA/Spec Sheet.
• Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.
• Molecular weight (item): Not specified for this item; refer to CoA/Spec Sheet.

Literature/computed reference values (for professional planning; verify experimentally)

• State: Typically a crystalline solid (amino acids commonly form zwitterionic crystals).
• Acid–base behavior: Neutral α-amino acids typically exhibit pKa(COOH) ~2.0–2.5 and pKa(NH3+) ~9.0–9.7 (literature, phenylalanine-like). The para-ethynyl substituent is non-ionizable and only weakly affects these values.
• Isoelectric point (pI): Expected in the ~5.5–6.0 range for neutral aromatic amino acids (literature guidance).
• Solubility profile: As a zwitterion, sparingly soluble in pure water near pI; solubility increases at acidic (e.g., pH 2) or basic (e.g., pH 10) pH and in water/alcohol mixtures; poor solubility in nonpolar solvents (literature, amino acid behavior).
• UV/Vis: Aromatic ring gives UV absorption near 257–262 nm; para-alkynyl substitution slightly shifts/extends absorbance (literature, qualitative).
• Stability: Thermally stable as a solid when dry; prolonged heating can induce racemization and decomposition (general amino acid behavior). Terminal alkynes are stable under ambient conditions but can undergo oxidative dimerization under strongly basic, oxygenated conditions.

Practical notes

• For accurate solubility, optical rotation, and water content, consult the item’s CoA/Spec Sheet. Prepare solutions by pH adjustment rather than forcing dissolution with strong organic solvents.

Quality and Grades

Item-specific quality details (grade, purity, stabilizers) are not specified for this product; refer to the CoA/Spec Sheet for definitive specifications, chromatographic purity, water content, and optical rotation/enantiomeric excess.

Guidance for interpreting common grades (general)

• Research grade: Suitable for most synthetic chemistry, bioconjugation method development, and preliminary biochemical experiments.
• Peptide synthesis grade: Tight control of enantiomeric excess, metal content, and residual solvents; often provided as protected derivatives (e.g., Fmoc-L-p-ethynylphenylalanine) for SPPS. Low levels of UV-absorbing impurities are advantageous for analytical monitoring.
• Analytical grade: Greater documentation of identity and purity (HPLC/UPLC, NMR, HRMS), sometimes including chiral purity and residual water.

What to check on the CoA for this item

• Identity: 1H/13C NMR, HRMS, and, when applicable, optical rotation for L-configuration.
• Purity: HPLC area% and any noted byproducts (e.g., Glaser-dimerized side chain impurities).
• Residual solvents and water: Karl Fischer (if reported) and GC headspace.
• Inorganic content: Residual copper/palladium (if synthesized via coupling) may be reported.

Stabilizers/antioxidants

• None are indicated in the Product Data. If present, they will be listed on the CoA; stabilizers can affect downstream copper-catalyzed click reactions and should be considered during purification or formulation.

Reaction and Applications

Key utility arises from the terminal alkyne as a bioorthogonal handle combined with an L-α-amino acid backbone.

Research applications (literature/general)

• Bioorthogonal labeling: The terminal alkyne enables Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) to attach fluorophores, affinity tags, or crosslinkers to proteins/peptides incorporating p-ethynylphenylalanine.
• Chemical proteomics: Site-specific conjugation for pulldown, enrichment, or imaging after genetic code expansion or post-synthetic peptide modification.
• Raman/IR probes: The –C≡C–H stretch provides a useful vibrational reporter in the cellular “silent” region (~2100–2200 cm−1; literature), enabling label-free detection when incorporated into peptides.
• Crosslinking and polymer conjugation: Acts as an alkyne handle for thiol–yne and radical additions (with appropriate initiators), as well as for Glaser–Hay homocoupling to diynes under oxidative conditions (not typically used on biomolecules).

Synthetic chemistry roles

• Building block for SPPS: The free amino acid can be converted to Fmoc/Boc-protected forms; the alkyne generally withstands standard coupling/deprotection, avoiding strong oxidants or radical conditions.
• Small-molecule diversification: N-acylation, esterification, and amidation reactions install the residue into tailored scaffolds.

Practical considerations

• For CuAAC, copper chelation by the amino acid backbone is modest; employ stabilizing ligands (e.g., TBTA/THPTA) and sodium ascorbate to generate Cu(I) in situ.
• Protect the alkyne during multi-step synthesis if conditions risk addition or oxidation (e.g., as a TMS-alkyne, then deprotect with mild base/fluoride).

Reaction Conditions

General literature guidance for common transformations involving p-ethynylphenylalanine (verify and optimize per system):

• CuAAC (azide–alkyne click) on peptides/proteins containing this residue:

  • Solvent: Aqueous buffer (e.g., 50 mM phosphate or HEPES, pH 7.0–7.5), optional 0–10% t-BuOH/DMSO to solubilize azide partner.
  • Catalysis: CuSO4 (50–200 µM) + sodium ascorbate (0.5–5 mM) with a Cu(I)-stabilizing ligand (e.g., TBTA 50–200 µM or THPTA 0.1–0.5 mM).
  • Temperature/time: RT, 15–120 min depending on reagent excess and diffusion.
  • Notes: Degas to limit oxidative side reactions; for sensitive proteins, use THPTA and minimal copper; remove copper post-reaction via chelators or desalting.

• SPPS coupling (protected derivative):

  • Solvent: DMF or NMP.
  • Activators: HATU/HBTU/COMU (3–5 equiv), DIPEA (4–8 equiv) at RT for 5–30 min cycles.
  • Notes: Monitor for alkyne integrity by LC–MS; standard Fmoc deprotection (20% piperidine/DMF) is tolerated.

• Glaser–Hay homocoupling (for small-molecule analog work):

  • Conditions: Cu(I)/amine (e.g., CuCl, TMEDA) under O2 in alcohol or THF at RT–50°C.
  • Notes: Not typically applied to biomolecules; can generate diyne impurities—control oxygen and copper exposure when not desired.

• Thiol–yne additions:

  • Photoinitiated (365–405 nm) in aqueous/organic mixtures; requires radical initiator and oxygen control.
  • Provides thioether-functionalized derivatives on the alkyne.

Safety and Handling

Authoritative safety information must be taken from the product SDS. The following are general, literature-based considerations for α-amino acids bearing terminal alkynes.

• Product Data safety fields: GHS classification, signal word, pictograms, and H-statements are not specified for this item; refer to SDS.
• Expected hazards (general): Low acute toxicity typical of amino acids; may cause irritation to eyes, skin, and respiratory tract as dust. Avoid inhalation and contact.
• PPE: Laboratory coat, nitrile gloves, and safety glasses. Use a dust mask/respirator if handling powders that may become airborne. Work in a fume hood when weighing or when performing reactions (e.g., copper-catalyzed click chemistry) to limit exposure to reagents and aerosols.
• Handling notes:
  • Avoid moisture uptake; hygroscopicity varies—keep container tightly closed.
  • Terminal alkynes can participate in copper-catalyzed reactions; store away from strong bases and strong oxidants.
  • Minimize prolonged exposure to elevated temperature or basic media to avoid racemization.
• First aid (general):
  • Skin/eye contact: Rinse with water for several minutes; remove contaminated clothing; seek medical advice if irritation persists.
  • Inhalation: Move to fresh air; obtain medical attention if symptoms occur.
  • Ingestion: Rinse mouth; seek medical advice if unwell.
• Fire safety: Organic solid; use water spray, CO2, dry chemical, or foam. Combustion may produce CO/CO2 and nitrogen oxides.
• Spill response: Avoid dust generation; collect mechanically; wash residue with water while preventing environmental release of reaction additives (e.g., copper salts).

Always defer to the SDS for classifications, exposure limits, and emergency procedures.

Solvent Selection

Chemical nature and polarity

• Zwitterionic α-amino acid with an aromatic, para-ethynyl side chain. At neutral pH near its pI, aqueous solubility is limited; solubility improves in acidic (NH3+ dominates) or basic (COO− dominates) water.

Recommended media (general guidance)

• Aqueous buffers adjusted away from pI:
  • Acidic dissolution: Water with 0.1–0.5 equiv HCl or acetate buffer pH 2–3.
  • Basic dissolution: Water with 0.1–0.5 equiv NaOH or borate buffer pH 9–10.
• Water/alcohol mixtures: 50–70% water with methanol or ethanol can assist dissolution while maintaining compatibility with bioconjugation.
• Poor choices: Nonpolar/aprotic solvents (hexanes, toluene, MTBE) and weakly polar solvents (DCM, CPME) are generally unsuitable for the free amino acid.

Comparative notes (literature-based)

• Versus phenylalanine: Similar aqueous behavior; the ethynyl group slightly increases hydrophobicity but does not impart organic solubility to the zwitterion.
• Protected derivatives (e.g., Fmoc-, methyl ester) are markedly more soluble in organic solvents (DMF, DCM, MeCN) and are preferred for SPPS or solution-phase peptide couplings.

Practical tips

• Dissolve by pH adjustment rather than vigorous heating to avoid racemization.
• For click chemistry in biological media, maintain aqueous buffers containing minimal organic cosolvent (≤10% DMSO/EtOH) to preserve biomolecular integrity.
• Filter sterilize (0.22 µm) for cell-free bioconjugation workflows; avoid copper contamination unless CuAAC is intended.

Storage and Reconstitution

Storage (from Product Data)

• Store at −80°C.
• Shipped on dry ice packs + cold packs.

General handling

• Upon receipt, keep frozen. Allow the container to equilibrate to room temperature in a desiccator before opening to minimize moisture condensation.
• Reseal promptly under dry air or inert gas. Return to −80°C for long-term storage. For frequent access, prepare working aliquots to avoid repeated freeze–thaw cycles.

Reconstitution (general guidance)

• Solvent: Use water adjusted with dilute acid (e.g., HCl) or base (e.g., NaOH) to move away from the isoelectric point and facilitate dissolution. Aim for 10–100 mM stocks depending on intended use.
• Filtration: For bioconjugation, sterile-filter through 0.22 µm to remove particulates and potential microbial contaminants.
• Stability of solutions: Store aliquoted solutions at −80°C. Limit thaw cycles; discard if turbidity, color change, or precipitate persists after gentle warming and pH readjustment.

Compatibility notes

• Avoid prolonged exposure to strong bases or elevated temperature to limit racemization. Protect from strong oxidants and radical initiators to preserve the terminal alkyne.

Documentation

• For item-specific limits (water content, residual solvents, enantiomeric excess, assay), consult the CoA/Spec Sheet. Always follow the SDS for safe handling during reconstitution.

Structure and Identity

p-Ethynylphenylalanine is a para-alkynylated, noncanonical α-amino acid derived from phenylalanine, featuring a terminal alkyne substituent at the para position of the aromatic ring.

• Item-specific identifiers (from Product Data):

  • SKU: P656480
  • CAS: 278605-15-5
  • Category: Small molecules and compound library (research use only)
  • SMILES: Not specified for this item; refer to CoA/Spec Sheet.
  • InChIKey: Not specified for this item; refer to CoA/Spec Sheet.

• Literature/commonly reported identity (for reference; verify against CoA):

  • Common name: p-ethynyl-L-phenylalanine (para-ethynyl-L-phenylalanine; pEthF)
  • Structural features: α-amino acid (–NH2 and –CO2H on the α-carbon), benzyl side chain bearing a para-ethynyl (–C≡CH) group; side chain is non-ionizable and weakly hydrophobic; terminal alkyne is bioorthogonal and click-reactive.
  • 2D description (verbal): A central chiral α-carbon (L-configuration) bonded to –NH2, –CO2H, –H, and a benzyl group; the benzyl phenyl ring bears a –C≡CH substituent at the position para to the benzylic carbon.
  • Molecular formula (literature): C11H11NO2 (verify against CoA/Spec Sheet).
  • Molecular weight (literature): ~189.21 g/mol (verify against CoA/Spec Sheet).

Notes

• Stereochemistry: Typically supplied as the L-enantiomer for biological incorporation; confirm configuration on the CoA.
• If isotopic labeling, salt form, or protecting groups (e.g., Fmoc, Boc, methyl ester) are required, select the corresponding protected derivative rather than this free amino acid.

Synthetic Utility

Functional group synopsis

• α-Amino acid core: Enables amide bond formation into peptides and peptidomimetics. Protecting groups (Fmoc/Boc for the amine, methyl/tert-butyl esters for the acid) control chemoselectivity.
• Para-ethynyl arene: Terminal alkyne supports click chemistry, oxidative coupling (Glaser–Hay), hydrofunctionalizations (thiol–yne, hydrosilylation), and metal-catalyzed additions.

Retrosynthetic/forward design roles (literature)

• SPPS monomer: Convert to Fmoc-L-p-ethynylphenylalanine (Fmoc-PeF-OH) for Fmoc/tBu SPPS; the alkyne tolerates standard couplings (HBTU/HATU/COMU) and deprotections (piperidine, TFA) when carefully controlled.
• Divergent conjugation node: Install p-ethynylphenylalanine into a scaffold, then diversify late-stage by CuAAC with a library of azides (fluorophores, PEGs, biotin, handles) for rapid SAR mapping.
• Orthogonal protection: Temporary masking of the alkyne as TMS–C≡C– (TMS deprotected with TBAF or mild base) allows exposure to conditions incompatible with terminal alkynes.

Practical tips

• Avoid strong bases and prolonged heat to limit epimerization at the α-carbon.
• If performing metal-catalyzed reactions on the alkyne, protect the amino/acid functions (or use the fully protected derivative) to prevent coordination/side reactions.
• For analytical tracking, exploit aryl–alkyne UV absorbance and the diagnostic IR band of the C≡C–H stretch; LC–MS readily detects the +N3 adduct (+41.0 Da) after CuAAC with small azides.

Target Specificity

Not applicable. This product is a small-molecule amino acid, not an antibody, probe with defined biological target binding, or an assay-specific reagent with inherent selectivity. No antigen/epitope, clone, isotype, or species reactivity information is provided in the Product Data. Any target engagement arises only after incorporation into biomolecules and subsequent conjugation to targeting ligands.

Domande frequenti

How should this product be stored?

Store at ?80 °C. Ultra-low temperature storage is required to maintain the specified shelf life.

How is this product shipped?

This product ships frozen with dry ice and cold packs. Unpack on arrival and transfer it to the storage condition stated above; handle dry ice with insulated gloves in a ventilated area.

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

The CAS Number is 278605-15-5, the molecular formula is C11H11NO2, and the molecular weight is 189.21 g/mol.

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.