RB-OPD (NO-red) is an o-phenylenediamine (OPD) type nitric oxide (NO) fluorescent probe with high sensitivity and selectivity (λex=550 nm, λem=590 nm).

Physicochemical Properties

Molecular Formula	C34H36N4O2
Molecular Weight	532.68
Exact Mass	532.283
CAS #	1034863-51-8
PubChem CID	102406797
Appearance	Off-white to light yellow solid powder
LogP	6.3
Hydrogen Bond Donor Count	1
Hydrogen Bond Acceptor Count	5
Rotatable Bond Count	7
Heavy Atom Count	40
Complexity	838
Defined Atom Stereocenter Count	0
SMILES	C1C=CC=C2C=1C(=O)N(C1C=CC=CC=1N)C12C2C(OC3C1=CC=C(C=3)N(CC)CC)=CC(=CC=2)N(CC)CC
InChi Key	FLFCPVCPMCLBEW-UHFFFAOYSA-N
InChi Code	InChI=1S/C34H36N4O2/c1-5-36(6-2)23-17-19-27-31(21-23)40-32-22-24(37(7-3)8-4)18-20-28(32)34(27)26-14-10-9-13-25(26)33(39)38(34)30-16-12-11-15-29(30)35/h9-22H,5-8,35H2,1-4H3
Chemical Name	2-(2-aminophenyl)-3',6'-bis(diethylamino)spiro[isoindole-3,9'-xanthene]-1-one
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

ln Vitro

RB-OPD (compound 1) can be used to detect NO in aqueous solution under physiologically normal conditions due to its "turn-on" type fluorogenic and chromogenic behavior toward NO. Its sensitivity and selectivity are quite high. In order to function as a "masked" NO-sensitive modulator, o-phenylenediamine, a NO-reactive group in lactam form, and rhodamine B spirolactam, a possible strong fluorophore and chromophore, make up NO-red.

References

[1]. Fluorogenic and chromogenic rhodamine spirolactam based probe for nitric oxide by spiro ring opening reaction. Org Lett. 2008 Jun 19;10(12):2357-60.

Solubility Data

Solubility (In Vitro)

DMSO: 25 mg/mL (46.93 mM)

Solubility (In Vivo)

Solubility in Formulation 1: 2.5 mg/mL (4.69 mM) in 10% DMSO + 40% PEG300 +5% Tween-80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication. 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	1.8773 mL	9.3865 mL	18.7730 mL
	5 mM	0.3755 mL	1.8773 mL	3.7546 mL
	10 mM	0.1877 mL	0.9386 mL	1.8773 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.