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RatioWorks™ PDMPO

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pH dependent Emission spectra of PDMPO. 
pH dependent Excitation spectra of PDMPO. 
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Physical properties
Molecular weight366.41
Spectral properties
Excitation (nm)333
Emission (nm)531
Storage, safety and handling
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22
StorageFreeze (< -15 °C); Minimize light exposure


Molecular weight
Excitation (nm)
Emission (nm)
The existing pH probes are ill-adapted to study acidic organelles such as lysosomes, endosomes, spermatozoa and acrosomes because their fluorescence is significantly reduced at lower pH. In addition, most of the existing pH probes (such as BCECF and SNARF) are not selectively localized in acidic organelles. The growing potential of ratio imaging is significantly limited by the lack of appropriate fluorescent probes for acidic organelles although ratio imaging has received intensive attention in the past few decades. PDMPO [2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole] is the same molecule to LysoSensor Yellow/Blue, and characterized as acidotropic dual-excitation and dual-emission pH probe. It emits intense yellow fluorescence at lower pH and gives intense blue fluorescence at higher pH. This unique pH-dependent fluorescence makes PDMPO an ideal pH probe for acidic organelles with pKa = 4.47. PDMPO selectively labels acidic organelles (such as lysosomes) of live cells and the two distinct emission peaks can be used to monitor the pH fluctuations of live cells in ratio measurements. Additionally, the very large Stokes shift and excellent photostability of PDMPO make PDMPO an excellent fluorescent acidotropic reagent for fluorescence imaging. The unique fluorescence properties of PDMPO might give researchers a new tool with which to study acidic organelles of live cells. PDMPO can be well excited by the violet laser at 405 nm for flow cytometric applications.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of RatioWorks™ PDMPO to given concentration. Note that volume is only for preparing stock solution. Refer to sample experimental protocol for appropriate experimental/physiological buffers.

0.1 mg0.5 mg1 mg5 mg10 mg
1 mM272.918 µL1.365 mL2.729 mL13.646 mL27.292 mL
5 mM54.584 µL272.918 µL545.837 µL2.729 mL5.458 mL
10 mM27.292 µL136.459 µL272.918 µL1.365 mL2.729 mL

Molarity calculator

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Spectral properties

Excitation (nm)333
Emission (nm)531

Product Family

NameExcitation (nm)Emission (nm)
RatioWorks™ PH165463641



View all 6 citations: Citation Explorer
Mannose ameliorates experimental colitis by protecting intestinal barrier integrity
Authors: Dong, Lijun and Xie, Jingwen and Wang, Youyi and Jiang, Honglian and Chen, Kai and Li, Dantong and Wang, Jing and Liu, Yunzhi and He, Jia and Zhou, Jia and others,
Journal: Nature communications (2022): 1--17
Mycobacterium tuberculosis Utilizes Host Histamine Receptor H1 to Modulate Reactive Oxygen Species Production and Phagosome Maturation via the p38MAPK-NOX2 Axis
Authors: Mo, Siwei and Guo, Jiubiao and Ye, Taosheng and Zhang, Ximeng and Zeng, Jiang and Xu, Yuzhong and Peng, Bin and Dai, Youchao and Xiao, Wei and Zhang, Peize and others,
Journal: Mbio (2022): e02004--22
The molecular basis for pore pattern morphogenesis in diatom silica
Authors: Heintze, Christoph and Babenko, Iaroslav and Suchanova, Jirina Zackova and Skeffington, Alastair and Friedrich, Benjamin and Kroeger, Nils
Journal: (2022)
An intimate view into the silica deposition vesicles of diatoms
Authors: Heintze, Christoph and Formanek, Petr and Pohl, Darius and Hauptstein, Jannes and Rellinghaus, Bernd and Kr{\"o}ger, Nils
Journal: BMC Materials (2020): 1--15
A New View into the Silica Deposition Vesicles of Diatoms
Authors: Kr{\"o}ger, N and Heintze, C and Formanek, P and Pohl, D and Hauptstein, J and Rellinghaus, B
Journal: (2020)
iTRAQ-based proteomic analysis of the metabolism mechanism associated with silicon response in the marine diatom Thalassiosira pseudonana
Authors: Du, Chao and Liang, Jun-Rong and Chen, Dan-Dan and Xu, Bin and Zhuo, Wen-Hao and Gao, Ya-Hui and Chen, Chang-Ping and Bowler, Chris and Zhang, Wen
Journal: Journal of proteome research (2014): 720--734


View all 8 references: Citation Explorer
Using LysoSensor Yellow/Blue DND-160 to sense acidic pH under high hydrostatic pressures
Authors: DePedro HM, Urayama P.
Journal: Anal Biochem (2009): 359
Acidic microclimate pH distribution in PLGA microspheres monitored by confocal laser scanning microscopy
Authors: Ding AG, Schwendeman SP.
Journal: Pharm Res (2008): 2041
Heterogeneity of acid secretion induced by carbachol and histamine along the gastric gland axis and its relationship to [Ca2+]i
Authors: Perez-Zoghbi JF, Mayora A, Ruiz MC, Michelangeli F.
Journal: Am J Physiol Gastrointest Liver Physiol (2008): G671
Platelet-activating factor stimulates cytoplasmic alkalinization and granule acidification in human eosinophils
Authors: Bankers-Fulbright JL, Kephart GM, Bartemes KR, Kita H, O'Grady SM.
Journal: J Cell Sci (2004): 5749
Divalent cations regulate acidity within the lumen and tubulovesicle compartment of gastric parietal cells
Authors: Gerbino A, Hofer AM, McKay B, Lau BW, Soybel DI.
Journal: Gastroenterology (2004): 182
Silica transport in the demosponge Suberites domuncula: fluorescence emission analysis using the PDMPO probe and cloning of a potential transporter
Authors: Schroder HC, Perovic-Ottstadt S, Rothenberger M, Wiens M, Schwertner H, Batel R, Korzhev M, Muller IM, Muller WE.
Journal: Biochem J (2004): 665
Elevated lysosomal pH in neuronal ceroid lipofuscinoses (NCLs)
Authors: Holopainen JM, Saarikoski J, Kinnunen PK, Jarvela I.
Journal: Eur J Biochem (2001): 5851
A novel fluorescent silica tracer for biological silicification studies
Authors: Shimizu K, Del Amo Y, Brzezinski MA, Stucky GD, Morse DE.
Journal: Chem Biol (2001): 1051