TPE-MI (Tetraphenylethene maleimide) is intrinsically non-fluorescent until conjugated to thiols via maleimide. TPE-MI fluorescence is activated upon labeling of free cysteine thiols that are normally buried in the core of globular proteins exposed upon unfolding. TPE-MI may be utilized to measure cellular unfolded protein load. TPE-MI can report imbalanced protein balance in induced pluripotent stem cell models of Huntington's disease and in cells transfected with mutant huntingtin exon 1 before the formation of visible aggregates. TPE-MI also detects protein damage following dihydroartemisinin studies in malaria parasites.

Physicochemical Properties

Molecular Formula	C31H23NO2
Molecular Weight	441.52
Exact Mass	441.172
CAS #	1245606-71-6
PubChem CID	99867104
Appearance	Light yellow to yellow solid powder
Density	1.2±0.1 g/cm3
Boiling Point	565.7±29.0 °C at 760 mmHg
Flash Point	228.0±16.6 °C
Vapour Pressure	0.0±1.5 mmHg at 25°C
Index of Refraction	1.665
LogP	7.74
Hydrogen Bond Donor Count	0
Hydrogen Bond Acceptor Count	2
Rotatable Bond Count	5
Heavy Atom Count	34
Complexity	764
Defined Atom Stereocenter Count	0
SMILES	O=C1C([H])=C([H])C(N1C1C([H])=C([H])C(=C([H])C=1[H])/C(/C1C([H])=C([H])C([H])=C([H])C=1[H])=C(\C1C([H])=C([H])C([H])=C([H])C=1[H])/C1C([H])=C([H])C(C([H])([H])[H])=C([H])C=1[H])=O
InChi Key	CIMVFJJQFXGASK-NVQSTNCTSA-N
InChi Code	InChI=1S/C31H23NO2/c1-22-12-14-25(15-13-22)30(23-8-4-2-5-9-23)31(24-10-6-3-7-11-24)26-16-18-27(19-17-26)32-28(33)20-21-29(32)34/h2-21H,1H3/b31-30+
Chemical Name	1-[4-[(E)-2-(4-methylphenyl)-1,2-diphenylethenyl]phenyl]pyrrole-2,5-dione
HS Tariff Code	2934.99.9001
Storage	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.
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

Targets	Plasmodium
ln Vitro	TPE-MI is not luminous by nature until maleimide is used to conjugate it to a thiol. When free cysteine thiols, which are often hidden in the center of globular proteins and become visible following unfolding, are labeled, TPE-MI fluorescence is triggered [1]. In live HeLa cells, TPE-MI (50 μM; 0–60 min) displays a uniform cytoplasmic labeling pattern, with lower label concentrations in the ER area and lower label levels in the nucleus, which is believed to be a primary location for protein synthesis and folding [1]. Compared to the non-pathogenic 25Q form of Httex1, the mutant 97Q form of Httex1 exhibits an increased TPE-MI fluorescence signal at high expression levels [1]. TPE-MI possesses both selective thiol reactivity and the aggregation-induced emission (AIE) phenomenon since it is made up of the thiol-reactive group maleimide (MI) and the fluorescein tetraphenylethane (TPE) [2].
References	[1]. Chen MZ, et al. A thiol probe for measuring unfolded protein load and proteostasis in cells. Nat Commun. 2017;8(1):474. Published 2017 Sep 7. [2]. Hu Q, et al. In Situ Monitored Vortex Fluidic-Mediated Protein Refolding/Unfolding Using an Aggregation-Induced Emission Bioprobe. Molecules. 2021;26(14):4273. Published 2021 Jul 14.

Solubility Data

Solubility (In Vitro)

DMSO : 44.15 mg/mL (100.00 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.5 mg/mL (5.66 mM) (saturation unknown) in 10% DMSO + 40% PEG300 +5% Tween-80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 + to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	2.2649 mL	11.3245 mL	22.6490 mL
	5 mM	0.4530 mL	2.2649 mL	4.5298 mL
	10 mM	0.2265 mL	1.1325 mL	2.2649 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.