IC50: 1.9 μM (Dynamin I)[1]
Dynamin I (GTPase, IC50 = 1.9 ± 0.2 μM for dynamin I from sheep brain) [1]; Dynamin II (presumed, as RME inhibition correlates with dynamin II function) [1]; Bacterial cell membrane (nonspecific, via surfactant action, with activity correlated to critical micelle concentration) [2]

Trimethyloctadecylammonium bromide (1 μM-100 μM; 10 min) suppresses the endocytosis of EGF-A488 in COS-7 cells, with an IC50 value of 16 μM[1]. In A431 cells, trimethyloctadecylammonium bromide (30 μM; 10 min; 37 °C) has no effect on EGFR activation and only slightly alters EGFR autophosphorylation[1]. According to the CMC assay, Staphylococcus aureus is inhibited by trimethyloctadecylammonium bromide (stearyl-) at concentrations of 0.33 mM and 59.5 nM, respectively[2].

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In vitro, Trimethyloctadecylammonium bromide (OctMAB) inhibited the GTPase activity of dynamin I purified from sheep brain with an IC50 of 1.9 ± 0.2 μM, showing increased potency compared to shorter-chain analogs (myristyl: 3.1 ± 0.2 μM; dodecyl: 9.0 ± 1.4 μM). It competitively inhibited phospholipid (PS) stimulation of dynamin I GTPase activity with a Ki of 940 ± 25 nM, and noncompetitively inhibited with respect to GTP. The compound prevented dynamin I binding to liposomes in a concentration-dependent manner (50% block at 100 μM in sedimentation assay). It also blocked the plasma membrane localization of the dynamin I PH domain (GFP-dyn I-PH) in HeLa cells at 30 μM, while myristic acid had no effect. Trimethyloctadecylammonium bromide inhibited receptor-mediated endocytosis of transferrin and EGF in HeLa, A431, and COS-7 cells, with a rank order of potency (OctMAB > MiTMAB > DoTMAB) matching dynamin inhibition. It did not affect Tf or EGF binding to cell surface receptors, nor did it inhibit EGFR autophosphorylation. In synaptosomes, it selectively blocked synaptic vesicle endocytosis (retrieval efficiency reduced to 0.76 ± 0.08) without affecting Ca2+-dependent glutamate exocytosis. Electron microscopy of synaptosomes treated with the compound (30 μM for 5 min) followed by KCl depolarization showed massive depletion of synaptic vesicles, confirming SVE blockade. Trimethyloctadecylammonium bromide (as stearyltrimethylammonium bromide) showed bactericidal activity against Staphylococcus aureus in aqueous solution with a critical kill dilution (CKD) of 1:60,000 (experimental) and a molar CKD of 5.95 × 10⁻⁸ M. Its activity (CKD/CMC) was 2.58 × 10⁻⁴. In partition systems with aliphatic alcohols (15% cetyl or stearyl alcohol), the compound was often ineffective (CKD <15) due to low aqueous phase concentration, but activity increased with addition of hydrocarbons (mineral oil or white petrolatum). The myristyl derivative was more effective overall than the stearyl derivative in these systems. [1][2]

In vivo, Trimethyloctadecylammonium bromide was not directly tested in animals in the provided references. However, a related compound (MiTMAB) was shown to block albumin endocytosis in isolated perfused rat kidney, suggesting potential in vivo utility for endocytosis inhibition. No specific in vivo data for OctMAB are reported. [1]

Trimethyloctadecylammonium bromide (OctMAB) was evaluated in a malachite green GTPase assay using purified dynamin I (20 nM) from sheep brain. Dynamin I was incubated in GTPase buffer (10 mM Tris-HCl, 10 mM NaCl, 2 mM Mg²⁺, 0.05% Tween 80, pH 7.5, with leupeptin and PMSF) with 0.3 mM GTP and test compound for 30 min at 37°C. Phosphatidylserine liposomes (1.2 μM) were used to stimulate activity. The reaction was terminated with EDTA, and released phosphate was detected by adding malachite green solution (ammonium molybdate, malachite green, HCl) and measuring absorbance at 650 nm. IC50 values were calculated from concentration-response curves. [1]
For phospholipid binding assay, dynamin I (520 nM) was incubated with PS liposomes (100 μM) in assembly buffer (1 mM EGTA, 30 mM Tris, 100 mM NaCl, 1 mM DTT, protease inhibitors) for 30 min at 22°C, then centrifuged at 14,000g for 15 min. Supernatant and pellet fractions were analyzed by SDS-PAGE and Coomassie staining. Trimethyloctadecylammonium bromide reduced dynamin in the pellet in a concentration-dependent manner. [1]
For bactericidal testing, a 1% stock solution of the quaternary ammonium compound was prepared in sterile distilled water. Serial dilutions were made, and the critical kill dilution (CKD) was determined using the AOAC phenol coefficient method against Staphylococcus aureus (FDA 209, ATCC 6538) at 37°C. The CKD is the highest dilution that kills the test organism in 10 min but not in 5 min. Results were read after 48 hr incubation in Letheen broth. [2]

Trimethyloctadecylammonium bromide was tested in receptor-mediated endocytosis assays using COS-7, HeLa, and A431 cells. Cells were serum-starved overnight, preincubated with the compound (typically 30 μM or various concentrations) for 10–15 min at 37°C, then incubated with fluorescently labeled transferrin (Tf-TxR, 5 μg/ml) or EGF (EGF-A488, 1 μg/ml) for 10–15 min at 37°C. After acid wash to remove surface-bound ligand, cells were fixed with 4% paraformaldehyde and imaged. Quantitative analysis of EGF endocytosis in COS-7 cells used an automated process with 96-well plates, preincubation with varying drug concentrations, then EGF-A488 (1 μg/ml) for 10 min at 37°C. After acid wash and fixation, nuclei were stained with DAPI, and integrated fluorescence intensity per cell was measured. The IC50 for RME inhibition by MiTMAB was 20.9 ± 3.2 μM; OcTMAB was slightly more potent but exact IC50 not given. [1]
For synaptosomal assays, rat brain Percoll-purified synaptosomes were preincubated with 30 μM Trimethyloctadecylammonium bromide for 10 min, then stimulated with 30 mM KCl. FM2-10 uptake (endocytosis) was measured using a loading and unloading protocol. Glutamate release (exocytosis) was measured by enzyme-linked fluorescent detection. Retrieval efficiency (endocytosis/exocytosis) was significantly reduced to 0.76 ± 0.08. [1]
For bactericidal testing of partitioned systems, the aqueous phase from each partition study was diluted 1:15, and further dilutions were made to determine CKD against S. aureus. For creams, a 1:30 or greater dilution was prepared in sterile distilled water, shaken, phases allowed to separate for 1 hr, then the lower phase sampled for testing. [2]

[1]. Myristyl trimethyl ammonium bromide and octadecyl trimethyl ammonium bromide are surface-active small molecule dynamin inhibitors that block endocytosis mediated by dynamin I or dynamin II. Mol Pharmacol. 2007 Dec;72(6):1425-39.

[2]. Bactericidal properties of quaternary ammonium compounds in dispersed systems. J Pharm Sci. 1977 May;66(5):696-9.

Trimethyloctadecylammonium bromide (stearyltrimethylammonium bromide) was characterized for its critical micelle concentration (CMC), which was 3.3 × 10⁻⁴ M in aqueous medium. Its bactericidal activity, when normalized to CMC (CKD/CMC), was 2.58 × 10⁻⁴, suggesting a nonspecific physical mechanism of action (Ferguson’s principle). In partition systems with aliphatic alcohols (cetyl or stearyl alcohol), the compound’s aqueous phase concentration was low, leading to poor bactericidal effectiveness (CKD <15). Inclusion of 15% mineral oil or white petrolatum increased the corrected CKD (e.g., from <15 to 20–30 in some systems), indicating enhanced availability in the aqueous phase. The compound’s bactericidal activity correlated with its concentration in the aqueous phase. [2]

C21H46BRN

392.51

391.281

1120-02-1

15461-40-2 (Parent)

70708

White to off-white solid powder

~250 °C (dec.)(lit.)

3.958

0

1

17

23

204

0

SZEMGTQCPRNXEG-UHFFFAOYSA-M

InChI=1S/C21H46N.BrH/c1-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22(2,3)4;/h5-21H2,1-4H3;1H/q+1;/p-1

trimethyl(octadecyl)azanium;bromide

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : 10 mg/mL (25.48 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)