Larazotide acetate - 10mM in Water , Neuronal acetylcholine receptor; alpha3/beta4 partial agonist, CAS No.881851-50-9, Neuronal acetylcholine receptor; alpha3/beta4 partial agonist

CAS: 881851-50-9 Cat. No.: L654505 Fórmula: C₃₄H₅₉N₉O₁₂ Peso molecular: 785.89

GRADE & PURITY 10mM in Water

Storage

Desiccated,Store at -80°C

Shipped In

Dry ice packs + Cold packs

Visão geral

Larazotide acetate is a peptide which is an orally active zonulin antagonist. Larazotide acetate shows antiviral activity to varicella-zoster virus (VZV) with EC 50 s of 44.14 and 59.06 μM for strain OKA and 07-1, respectively. Larazotide acetate can be used for the research of celiac disease and infection .

In Vitro

Larazotide acetate (1-100 μM; 5 d) affects Vero cell growth. Larazotide acetate (1-100 μM; 3 d) shows antiviral activity to varicella-zoster virus (VZV) with EC 50 s of 44.14 and 59.06 μM for strain OKA and 07-1, respectively. Larazotide acetate (1 and 3 mM; 72 h) inhibits cytokine-induced tight junction permeability in Caco-2 cells. Larazotide acetate (12.5 mM; 1 h) inhibits PTG-induced ZO-1 redistribution and actin cytoskeletal rearrangement in IEC6 cells. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Cell Cytotoxicity AssayCell Line: Vero cell line Concentration: 1-100 μM Incubation Time: 5 days Result: Inhibited Vero cell growth with an CC 50 value of 82.5 μM.

In Vivo

Larazotide acetate (250 μg; i.p. twice a week for 7 weeks) inhibits intestinal permeability in gluten-sensitive transgenic mice . MCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal Model: HLA-HCD4/DQ8 double transgenic miceDosage: 250 μg Administration: Intraperitoneal injection; 250 μg twice a week for 7 weeks Result: Improved barrier function parameters and reduced macrophage counts in the lamina propria to control levels.

IC50& Target:Paracellular permeability

Specifications

Especificações e pureza

10mM in Water

Mecanismos bioquímicos e fisiológicos

Larazotide acetate is a peptide which is an orally active zonulin antagonist. Larazotide acetate shows antiviral activity to varicella-zoster virus (VZV) with EC 50 s of 44.14 and 59.06 μM for strain OKA and 07-1, respectively. Larazotide acetate can be u

Condições de armazenamento de armazenamento

Desiccated,Store at -80°C

Enviado em

Dry ice packs + Cold packs

Este produto requer transporte de cadeia fria. Serviços terrestres e outros serviços econômicos não estão disponíveis.

Tipo de ação

PARTIAL AGONIST

Mecanismo de ação

Neuronal acetylcholine receptor; alpha3/beta4 partial agonist

Nomes e identificadores

SMILES isoméricas

CC(C)C[C@@H](C(=O)N[C@@H](C(C)C)C(=O)N[C@@H](CCC(=O)N)C(=O)N1CCC[C@H]1C(=O)NCC(=O)O)NC(=O)[C@H](C(C)C)NC(=O)CNC(=O)CN.CC(=O)O

CAS alternativo

258818-34-7

Peso molecular

785.89

Application Protocols

No manufacturer-validated protocols are provided for this SKU. The following are literature-style, general protocols for common barrier-function assays using larazotide acetate. Adjust to your system and do not treat as item specifications.

1. TEER assay on Caco-2 monolayers (literature/general)

• Seed Caco-2 cells on collagen-coated Transwells; differentiate 14–21 days to achieve stable baseline TEER (e.g., >500 Ω·cm²; lab-specific).
• Prepare larazotide acetate stock (e.g., 10 mM in sterile water). Dilute into pre-warmed media to 0.1–30 µM.
• Pre-incubate monolayers 30–60 min with peptide. Challenge with barrier disruptor (e.g., gliadin digest or cytokine mixture) if applicable.
• Record TEER at baseline and at intervals up to 24–48 h, maintaining temperature during measurements.
• Analyze percent change vs. vehicle and positive control (e.g., EGTA).

2. Paracellular flux assay (FITC–dextran) (literature/general)

• After treatment as above, add FITC–dextran (e.g., 1 mg/mL, 4 kDa) apically.
• Collect basolateral samples at 30–120 min; measure fluorescence (Ex/Em 485/535 nm).
• Calculate Papp and compare across conditions.

3. Immunofluorescence of junctional proteins (literature/general)

• Fix cells (e.g., 4% PFA), permeabilize, block, and stain for ZO-1/occludin/claudins.
• Image by confocal microscopy; quantify junctional continuity and intensity.

General notes:

• Include vehicle and unrelated peptide controls.
• Confirm non-cytotoxicity at chosen concentrations.
• Keep DMSO ≤0.1% if used.

Biological Roles

No biological/biochemical roles are specified for this item. The following information reflects common literature usage of larazotide acetate strictly as a research tool compound (not for clinical use).

Literature/general overview:

• Pathway context: Larazotide acetate is widely used to interrogate the zonulin pathway that regulates tight junction dynamics in epithelial and endothelial barriers. It is often described as a modulator/antagonist that limits zonulin-induced increases in paracellular permeability.
• Cellular effects in vitro: In epithelial monolayers, treatment can preserve or restore tight junction integrity (e.g., maintenance of TEER and reduced tracer flux) under disruptive stimuli such as gliadin-derived peptides or proinflammatory cytokines, enabling mechanistic studies of barrier homeostasis.
• Junctional proteins: Studies frequently assess the distribution of claudins, occludin, and ZO-1 via immunofluorescence microscopy following exposure, to determine whether junctional scaffolds are stabilized.
• Signaling: Research explores upstream receptors and downstream effectors (e.g., PKC, MLCK, actomyosin contraction) implicated in junction opening/closure; larazotide is used to dissect these steps via pharmacologic perturbation.
• Model systems: Commonly applied to Caco-2, T84, HT-29/B6, and primary epithelial monolayers; also ex vivo tissues in Ussing chamber studies for transepithelial transport.

Caveats:

• Effects can be cell line- and stimulus-dependent; establish independent concentration–response and time-course in your model.
• Not a nutrient, supplement, or therapeutic. For research use only. Avoid extrapolating in vitro findings to in vivo outcomes without rigorous validation.

Buffer Applications

No manufacturer buffer system recommendations are provided for this SKU. The following guidance reflects common laboratory practice for peptide tool compounds and literature usage in epithelial barrier assays. These are not item specifications.

• Stock preparation (general):
  • Dissolve in sterile water or physiological buffer (e.g., PBS) to 1–10 mM. If solubility is limited at very high concentrations, pre-wet with a minimal volume of DMSO then dilute into water/buffer.
  • Filter-sterilize through 0.22 µm if using in cell culture. Aliquot and store at −80°C.
• Working solutions (literature examples):
  • Typical ranges: 0.05–50 µM in culture media depending on assay sensitivity and cell model. Start with a broad titration (e.g., 0.1, 0.3, 1, 3, 10, 30 µM).
  • Vehicle control: Match DMSO content if used (commonly ≤0.1%).
• Assay buffers (literature/general):
  • TEER: Use standard culture medium or specialized low-ionic-strength measurement buffers per instrument manufacturer; maintain temperature stability during readings.
  • Permeability: HBSS or Krebs buffer supplemented appropriately (e.g., HEPES) during FITC–dextran or lucifer yellow assays.
• pH and ionic strength:
  • Maintain pH 7.2–7.4 for live-cell assays; avoid extremes that can compromise both cells and peptide stability.
  • Include protease inhibitors only if compatible with your biological question and controls.

Always verify clarity and absence of precipitation after dilution into protein-containing media (FBS can alter peptide behavior). Prepare fresh working solutions immediately before use when possible.

Green Alternatives

As a non-volatile peptide supplied as a solid, larazotide acetate itself does not pose the solvent-related environmental burdens typical of organic reagents. Greener practice focuses on solvent choices and waste minimization during handling.

Greener handling strategies (literature/general):

• Prefer aqueous media: Use sterile water or physiological buffers as primary solvents. Avoid unnecessary organic co-solvents.
• Minimize DMSO: If DMSO is needed for concentrated stocks, prepare small aliquots and dilute promptly into aqueous buffers to reduce DMSO use and waste.
• Aseptic technique: Prevent microbial contamination to extend solution life, reducing repeated preparation and waste.
• Right-sizing: Prepare only the amount needed for near-term experiments; aliquot to avoid repeated freeze–thaw and discard.
• Low-energy storage discipline: Consolidate freezer space and avoid repeated door openings; track inventory to limit re-synthesis/re-order frequency.

Comparison (literature/general):

• Water/buffer vs. organic co-solvent
  • Environmental impact: Water/buffer has the lowest impact and VOC emissions; DMSO is relatively benign but still requires appropriate disposal.
  • Performance: Peptides generally dissolve well in aqueous media; DMSO assists in high-concentration stocks but adds cytotoxicity concerns in cell assays.

Waste and disposal:

• Aqueous peptide solutions can typically be disposed of as non-hazardous biochemical waste according to institutional policies; avoid drain disposal unless explicitly permitted. Deactivate biological additives (e.g., serum) per local procedures. Always follow local regulations and your EHS guidance.

Pharmaceutical Uses

No pharmacopeial status, excipient role, or formulation specifications are provided for this item. This product is supplied strictly for research use only and is not intended for human or veterinary use, diagnostics, or clinical applications.

Literature/general context for formulation research (non-clinical):

• Exploratory formulation studies: Researchers may investigate peptide stability in various buffers, simulate gastrointestinal conditions, or assess compatibility with common excipients to support preclinical, in vitro work. Such studies can inform handling in laboratory models but are not manufacturing specifications.
• Analytical controls: For formulation screening, identity/purity are typically monitored by LC–MS and UPLC, with peptide mapping if needed. Counterion (acetate) content can influence solubility and hygroscopicity.
• Delivery matrices (research): In vitro, the peptide is commonly dosed in aqueous media without complex carriers. For ex vivo tissue chambers, isotonic buffers are used.
• Regulatory note: There is no implication of GMP production, compendial compliance, or suitability as an API or excipient for any regulated use. Do not use in any product intended for administration to humans or animals.

If your work requires defined excipient compatibility, endotoxin limits, sterile manufacture, or stability data, contact technical support to discuss whether documentation beyond the standard CoA is available for SKU L654505.

Physical Properties

Item-specific specifications are not provided for this catalog entry. Where useful, general/literature expectations for peptides of this class are summarized. Do not treat literature values as item specifications; verify on the CoA/Spec Sheet for this SKU.

Item-specific (this lot/SKU):

• Molecular formula: Not specified for this item; refer to CoA/Spec Sheet.
• Molecular weight: Not specified for this item; refer to CoA/Spec Sheet.
• Appearance: Not specified for this item; refer to CoA/Spec Sheet.

Literature/general characteristics for larazotide acetate and similar octapeptides:

• Physical state: Typically supplied as a lyophilized solid (white to off-white) for peptides; actual appearance may vary (verify CoA).
• Solubility (literature): Readily soluble in water and aqueous buffers; frequently prepared as 1–10 mM stock in sterile water or dilute acid; increased solubility observed in DMSO if needed. Final aqueous working solutions are common.
• pH behavior (literature): Peptide solubility can be enhanced near neutral to slightly acidic pH (e.g., pH 5–7). Avoid strong base that may promote degradation of amide bonds over time.
• Partitioning (literature): Predominantly hydrophilic; negligible volatility; nonflammable.
• UV characteristics (literature): Lacks aromatic residues; minimal absorbance at 280 nm; quantify at 205–215 nm or by amino acid analysis/UPLC methods.
• Stability (literature): Stable when dry, protected from moisture and light at −20 to −80°C. In solution, stability depends on buffer, pH, temperature, and microbial load; sterile, aliquoted storage is recommended.

Any precise values (e.g., mp, density, refractive index) are generally not defined for peptides of this type and are not applicable for routine use.

Quality and Grades

Item-specific quality attributes have not been supplied for this listing; consult the CoA/Spec Sheet for lot-resolved details.

Item-specific (this SKU):

• Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.
• Counterion content and stoichiometry (acetate): Not specified for this item; refer to CoA/Spec Sheet.

General guidance for peptide product quality (literature/general):

• Purity conventions: Peptide purity is typically reported as % area by HPLC/UPLC at 214–220 nm. Common research grades include ≥90%, ≥95%, or ≥98% area. Peptides lacking aromatic residues show weak 280 nm absorbance; chromatograms should be reviewed at lower wavelengths.
• Identity confirmation: ESI/HRMS (m/z consistent with the peptide and expected adducts) and, where relevant, amino acid analysis or sequencing data. Note that acetate salt forms shift the exact mass and formula; refer to the CoA for the counted acetate equivalents.
• Counterions/additives: Lyophilized peptides may contain residual solvents (e.g., water), salts (acetate), or volatile buffers used during purification. These are normal and typically disclosed on the CoA.
• Endotoxin/bioburden: For cell-based work, low endotoxin and sterile filtration may be relevant. If required, request documentation or sterile processing.
• Impurities: Truncations, deletions, oxidations (e.g., Met/Ox if present; not in this sequence), and diastereomers/epimers can occur. Review chromatographic profiles for secondary peaks.

Recommendation: Align the required purity/analytical profile with your application (biophysical assays vs. cell culture) and verify all specifics with the CoA for SKU L654505.

Reaction and Applications

This product is a peptide tool compound rather than a classical synthetic reagent. No manufacturer application notes were provided for this SKU. The following use-cases summarize how larazotide acetate is commonly employed in research settings (literature/general). These are not item specifications.

• Epithelial barrier studies: Used to probe tight junction regulation in intestinal and other epithelial monolayers. Readouts include TEER (transepithelial electrical resistance) and paracellular flux assays (e.g., FITC–dextran, lucifer yellow).
• Zonulin pathway research: Functions as a modulator/antagonist in the zonulin-triggered opening/closing of tight junctions in vitro, enabling dissection of signaling cascades impacting claudins, occludin, and ZO-1 localization (immunostaining/IF co-localization).
• Inflammation and permeability models: Applied to cell or tissue models subjected to cytokines, bacterial products, or gliadin peptides to study barrier restoration or protection dynamics.
• Biophysical/structural assays: Employed in binding/competition or pathway activation studies to map upstream receptors and downstream kinases (e.g., PKC, MLCK) implicated in junctional remodeling.
• Methodological tips (general):
  • Prepare fresh sterile stocks; verify osmolality and pH of working media.
  • Establish a concentration–response curve; literature commonly explores sub- to low-micromolar ranges.
  • Include appropriate controls (vehicle, unrelated peptide, known junction modulators like EGTA as a positive disruptor control) and replicate across passages to control for monolayer maturity.

Note: This section describes research applications of a peptide tool compound and does not imply suitability for therapeutic or diagnostic use.

Reaction Conditions

Classical chemical “reaction conditions” are not pertinent to larazotide acetate, as it is supplied as a peptide tool compound. The following summarizes literature/general experimental conditions for biological assays where this peptide is used. These are not item specifications; optimize for your model.

• Stock solutions: 1–10 mM in sterile water or minimal DMSO, aliquoted and stored at −80°C. Thaw on ice and keep cold until use to minimize degradation.
• Dosing ranges (literature examples): Sub- to low-micromolar for cell monolayers (e.g., 0.1–30 µM). Establish a concentration–response curve and verify absence of cytotoxicity (e.g., by resazurin/CellTiter readouts) at selected concentrations.
• Incubation conditions: 37°C, 5% CO2 in standard culture media for epithelial cells. Pre-incubation 30–60 min before barrier challenge is commonly employed; time-courses from 1–48 h can be explored depending on readout.
• Readouts:
  • TEER: Measure baseline, dose, then track at defined intervals (e.g., every 15–60 min and at endpoint). Maintain temperature to avoid TEER drift.
  • Permeability: Apply tracer (FITC–dextran 4 kDa or lucifer yellow) apically; sample basolateral compartment at set times; compute apparent permeability (Papp).
  • IF microscopy: Fix and stain for ZO-1, occludin, claudins; assess junctional continuity and localization.
• Controls: Vehicle, disruptive positive control (e.g., EGTA), and irrelevant peptide controls.

Document exact media composition, serum content, passage number, and monolayer resistance criteria, as these strongly influence outcomes.

Safety and Handling

Safety data specific to this SKU have not been provided. Always consult the SDS for authoritative information.

GHS and hazard information (this item):

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

General safety guidance for research peptides (literature/general):

• Hazards: Low volatility solids; primary risks are dust generation, inhalation of particulates, skin/eye contact, and potential allergenicity/sensitization upon repeated exposure.
• PPE: Laboratory coat, nitrile gloves, safety glasses. Use a certified fume hood or ventilated enclosure when weighing to avoid aerosolization.
• Handling: Avoid moisture uptake; keep containers tightly closed. Minimize repeated vial openings; equilibrate to room temperature in a desiccator before opening to prevent condensation.
• Incompatibilities: Strong oxidizers, strong acids/bases for extended periods (may cause hydrolysis or side-chain modification). Avoid proteases and microbial contamination in aqueous solutions.
• First aid (overview, defer to SDS): If inhaled—move to fresh air; seek medical attention if symptoms occur. Skin/eyes—rinse with water for several minutes; remove contaminated clothing. If ingested—rinse mouth; seek medical advice.
• Spill/cleanup: Avoid dust; wet-wipe or use HEPA-filtered vacuum. Dispose of waste according to institutional and local regulations.

Storage and shipping (from Product Data):

• Storage: Desiccated, store at −80°C.
• Shipping: Dry ice packs + cold packs.
• Research Use Note: For research use only.

Solvent Selection

Larazotide acetate is a hydrophilic peptide typically handled in aqueous media. Item-specific solubility is not provided; consult the CoA. The following guidance is based on literature and peptide handling best practices.

• Primary solvents (literature/general):
  • Sterile water or buffer (e.g., PBS, HBSS) for working solutions.
  • Minimal DMSO may be used to prepare a concentrated stock (e.g., 10–50 mM) when required, then dilute into aqueous media to ≤0.1–0.5% DMSO in biological assays.
  • Brief exposure to 0.1% acetic acid or dilute HCl can assist initial dissolution before neutralization/buffer exchange.
• Miscibility: Water-miscible; DMSO co-solvent compatible. Avoid high organic content that can denature or aggregate peptides.
• Polarity class: Highly polar, nonvolatile; negligible vapor pressure.
• Practical selection tips:
  • For cell assays, use sterile, low-endotoxin water/buffers. Filter-sterilize through 0.22 µm after dissolution if sterility is critical.
  • Avoid basic pH (>8) and prolonged room-temperature exposure in solution to limit backbone hydrolysis.
  • Minimize freeze–thaw by aliquoting concentrated stocks.
• Comparison (literature/general):
  • Water/buffer: Best for immediate biological use; physiologically compatible.
  • DMSO: Aids solubilization for high-concentration stocks; ensure final DMSO tolerance in your model.
  • Alcohols (MeOH/EtOH): Generally not preferred for peptide stocks; risk of precipitation upon dilution and cytotoxicity in cell assays.

Always verify pH and clarity after dissolution; slight opalescence can indicate incipient aggregation—adjust ionic strength or dilute further.

Storage and Reconstitution

From Product Data (item-specific):

• Storage conditions: Desiccated, store at −80°C.
• Shipped in: Dry ice packs + cold packs.
• Research Use Note: For research use only.

Item-specific values such as exact solubility and appearance: Not specified for this item; refer to CoA/Spec Sheet.

General reconstitution guidance for research peptides (literature/general):

• Equilibrate the sealed vial to room temperature in a desiccator before opening to prevent moisture condensation.
• Reconstitution solvents: Sterile water or aqueous buffer (e.g., PBS) are preferred. If very high concentration stocks are required, dissolve in a minimal volume of DMSO first, then dilute with water/buffer.
• Stock concentration: Commonly 1–10 mM; verify clarity. Filter-sterilize (0.22 µm) for cell-based assays.
• Aliquoting: Dispense single-use aliquots in low-binding tubes to avoid adsorption and freeze–thaw.
• Storage of solutions: Store aliquots at −80°C. For short-term use, −20°C may be acceptable for days to a week; confirm stability empirically.
• Freeze–thaw: Avoid repeated cycles; thaw on ice and use promptly. Discard any solution showing turbidity/precipitation or unexpected pH changes.
• Light and oxidation: Protect from light. Work quickly at cold temperatures to limit degradation; avoid strong oxidants and extremes of pH.

Always consult the CoA/SDS for lot-specific guidance and implement aseptic technique when preparing solutions intended for cell culture.

Structure and Identity

Larazotide acetate is a research-grade peptide tool compound supplied as the acetate salt. It is widely referenced in the literature as an octapeptide derived from the zonulin pathway research space.

• SKU: L654505
• Product name: Larazotide acetate
• CAS: 881851-50-9
• Category: Small-molecule/compound library (peptidic tool compound)
• Molecular formula: Not specified for this item; refer to CoA/Spec Sheet.
• Molecular weight: Not specified for this item; refer to CoA/Spec Sheet.
• SMILES: Not specified for this item; refer to CoA/Spec Sheet.
• InChIKey: Not specified for this item; refer to CoA/Spec Sheet.

Structural features (literature/general):

• Peptide class: Short linear peptide; commonly cited sequence: Gly–Gly–Val–Leu–Val–Gln–Pro–Gly (GGVLVQPG) as the free peptide, supplied as its acetate salt. Exact counterion stoichiometry may vary by batch; consult CoA.
• Functional groups: Multiple amide bonds (peptide backbone), side-chain functionalities (aliphatic, amide-bearing), terminal amino/carboxyl groups depending on salt/termini status.
• Stereochemistry: Proteinogenic L-amino acids (literature/common for research peptides), unless otherwise noted on the CoA.

2D structure description (literature/general):

• A linear octapeptide chain with alternating small (Gly), aliphatic hydrophobic (Val, Leu), amide-containing polar (Gln), and conformationally constrained (Pro) residues. Side chains project alternately along the backbone, with proline introducing a local conformational kink. The acetate counterion(s) associate ionically with basic/terminal sites but are not covalently bound.

Synthetic Utility

Larazotide acetate is a finished peptide tool compound and is not typically used as a building block for further chemical synthesis. Consequently, classical synthetic transformations (e.g., cross-couplings, Grignard, lithiation) are not applicable.

Literature/general considerations for peptide-focused workflows:

• Derivatization: If chemical modification is desired (e.g., fluorescent labeling, biotinylation), strategies generally involve solution-phase coupling to N-terminus or specific side chains after deprotection. However, such modifications require custom synthesis and are outside the scope of this catalog item.
• Immobilization: For affinity or mechanistic studies, peptides may be immobilized on solid supports (e.g., NHS-activated resins) via terminal amines; binding interactions can then be profiled. This is typically done with tailored linkers and controlled orientation.
• Analytical development: The compound serves as a standard/positive control in bioassays probing tight junction dynamics. Method development may include stability-indicating LC methods (214–220 nm), MS detection, and peptide recovery studies from plastics (adsorption mitigation by low-binding tubes or carrier proteins if compatible with the assay).
• Retrosynthetic note: Solid-phase peptide synthesis (SPPS) using Fmoc/tBu chemistry is the common route for peptides of this size; purification by preparative RP-HPLC and conversion to the acetate salt via volatile buffers are typical. This information is provided for background only and does not imply that this product is intended for re-synthesis.

Target Specificity

No target specificity or biochemical binding data are provided for this item. The following reflects literature/general understanding of larazotide acetate as a pathway-focused tool compound.

• Pathway focus (literature/general): Used to modulate the zonulin-controlled regulation of tight junctions. Functional antagonism of zonulin-induced barrier opening has been reported in epithelial models.
• Molecular target: A single, well-defined molecular target with binding constants has not been universally established in the public domain; studies emphasize functional outcomes on tight junction proteins and cytoskeletal signaling cascades rather than a unique receptor-ligand pair.
• Cellular specificity: Acts at epithelial and endothelial barriers where tight junction machinery (claudins, occludin, ZO-1/2) orchestrates paracellular permeability. Effects are model- and context-dependent.
• Off-target considerations: As with many bioactive peptides, concentration, exposure time, and medium composition can influence apparent specificity. Employ orthogonal controls (e.g., siRNA/CRISPR to pathway components, kinase inhibitors) to validate mechanistic conclusions.

For definitive target identification, design experiments that integrate pharmacology (dose–response), genetics (loss/gain of function), and imaging/biophysics (co-localization, FRAP) while including proper negative controls and rescue experiments.