2,6-Pyridinedicarboxylic Acid: Properties, Uses & FAQs
2,6-Pyridinedicarboxylic Acid: Properties, Uses & FAQs
2,6-Pyridinedicarboxylic acid is a bifunctional aromatic dicarboxylic acid widely used as a metal chelator, luminescence sensitizer, and diagnostic biomarker in analytical and biochemical research.
- Common Name
- Dipicolinic acid (DPA)
- Molecular Formula
- C₇H₅NO₄
- Molecular Weight
- 167.12 g/mol
- CAS Number
- 499-83-2
- Appearance
- White to off-white crystalline powder
- Key Application
- Tridentate chelator for transition and lanthanide metals; bacterial endospore biomarker
Chemical Identity and Physical Properties
2,6-Pyridinedicarboxylic acid, commonly known as dipicolinic acid (DPA), is an aromatic heterocyclic compound with a pyridine ring bearing carboxylic acid groups at the 2- and 6-positions (CAS 499-83-2; molecular formula C₇H₅NO₄; MW 167.12 g/mol). The compound appears as a white to off-white crystalline powder. Its symmetrical structure places the ring nitrogen and both carbonyl oxygens in an arrangement ideal for tridentate coordination to metal ions. DPA is sparingly soluble in water at room temperature but dissolves readily in dilute aqueous base or hot water, and is soluble in polar organic solvents such as DMSO and methanol.
Mechanism of Metal Chelation
The chelating ability of 2,6-pyridinedicarboxylic acid arises from its tridentate N,O,O-donor set: the pyridine nitrogen and the two carboxylate oxygens simultaneously coordinate to a single metal center, forming two five-membered chelate rings. This geometry results in thermodynamically stable complexes with a wide range of di- and trivalent metal ions, including Fe³⁺, Cu²⁺, Ca²⁺, and lanthanide ions such as Tb³⁺ and Eu³⁺. The rigid planar aromatic backbone further enhances complex stability by minimizing entropic penalties upon coordination. In lanthanide systems, DPA acts as an antenna ligand, absorbing UV light and transferring energy to the lanthanide center, thereby sensitizing its characteristic sharp-line emission.
Key Research Applications
Bacterial Endospore Detection: DPA constitutes a major component of the core of bacterial endospores (particularly Bacillus and Clostridium species), where it forms a calcium–DPA complex that confers heat and radiation resistance. Its release upon spore germination or disruption is exploited in fluorescence-based bioassays for rapid detection of Bacillus anthracis (anthrax) spores, using terbium(III) luminescence as the detection signal.
Lanthanide Luminescence Probes: DPA and its derivatives are used to sensitize Tb³⁺ and Eu³⁺ luminescence in time-resolved fluorescence immunoassays (TR-FIA), DNA hybridization assays, and FRET-based biosensors, where the long luminescence lifetime of lanthanide complexes allows background fluorescence to be gated out.
Coordination Chemistry and MOF Synthesis: As a rigid ditopic linker, DPA is widely employed in the synthesis of metal-organic frameworks (MOFs) and coordination polymers with potential applications in gas storage, separation, and catalysis.
Analytical Chelation: DPA is used as a masking agent and titration auxiliary in complexometric analysis, and as a mobile-phase additive in ion-exchange and reversed-phase HPLC for separation of metal ions.
Storage, Handling, and Safety
2,6-Pyridinedicarboxylic acid should be stored in a tightly sealed container at room temperature (15–25 °C), protected from moisture and direct light. Standard laboratory personal protective equipment (lab coat, gloves, safety glasses) should be worn when handling the solid or its solutions. The compound is an irritant; avoid inhalation of dust and contact with skin and eyes. Consult the current Safety Data Sheet (SDS) before use. Dispose of waste according to local regulations for organic chemical waste. No special refrigeration is required for routine storage.
Ordering and Product Information
Aladdin Scientific supplies 2,6-pyridinedicarboxylic acid under SKU P109609. When placing an order, researchers should confirm the required quantity, purity grade, and any certificate of analysis (CoA) requirements with the sales team. Bulk quantities and custom purity specifications may be available upon request. For questions about compatibility with downstream applications or alternative grades, contact Aladdin's technical support team. Orders can be placed online or through your local distributor. Refer to our shipping and returns policies for information on cold-chain requirements (none required for this product) and return eligibility.
Frequently asked questions
What is the difference between 2,6-pyridinedicarboxylic acid and 2,5-pyridinedicarboxylic acid?
The two isomers differ in the position of the second carboxylic acid group on the pyridine ring. In the 2,6-isomer (dipicolinic acid), both carboxylate groups flank the nitrogen symmetrically, enabling efficient tridentate N,O,O chelation and antenna sensitization of lanthanide ions. The 2,5-isomer cannot adopt this tridentate geometry and therefore exhibits different coordination chemistry and photophysical properties. For metal chelation and spore-detection applications, the 2,6-isomer (P109609) is the relevant compound.
How should I prepare a stock solution of 2,6-pyridinedicarboxylic acid for use in cell-based assays?
DPA has limited solubility in neutral water, so we recommend dissolving it in a small volume of dilute NaOH (e.g., 0.1 M) to form the disodium salt, then diluting with the appropriate buffer to the desired concentration and adjusting pH to physiological range (7.0–7.4). Alternatively, a concentrated stock can be prepared in DMSO and diluted at least 100-fold into aqueous media to minimize solvent effects on cells. Filter-sterilize (0.22 µm) before use in cell culture. Verify final pH and osmolality before application.
Can 2,6-pyridinedicarboxylic acid be used to detect anthrax spores, and what is the detection principle?
Yes. DPA is a major constituent of Bacillus anthracis endospores, where it is stored as a calcium chelate. Upon spore lysis or germination, DPA is released into solution. In the standard terbium-based fluorescence assay, released DPA coordinates to Tb³⁺ ions, forming a highly luminescent complex that emits intensely at ~545 nm under UV excitation. Because the Tb³⁺–DPA complex has a long luminescence lifetime (millisecond range), time-gated detection effectively eliminates background autofluorescence, enabling sensitive and selective spore quantification.
What purity grade of 2,6-pyridinedicarboxylic acid is appropriate for HPLC and spectroscopic work?
For HPLC calibration standards and quantitative spectroscopic studies, a reagent-grade or higher purity product (typically ≥98%) is recommended to minimize interference from absorbing or fluorescing impurities. Please consult the Certificate of Analysis (CoA) supplied with product P109609 for lot-specific purity data. If ultra-high purity is critical for your application, contact Aladdin's technical team to inquire about available lots or custom purification options.
Is 2,6-pyridinedicarboxylic acid stable in aqueous solution over time?
Aqueous solutions of DPA are generally stable at neutral to mildly alkaline pH when stored at 4 °C in the dark and used within a few weeks. Prolonged exposure to strongly acidic or strongly alkaline conditions, heat, or UV light may lead to degradation. For long-term storage, it is preferable to keep the compound as a dry solid under sealed conditions and prepare fresh solutions as needed.
References
- Setlow P. Spores of Bacillus subtilis: their resistance to and killing by radiation, heat and chemicals. J Appl Microbiol. 2006.
- Pellegrino PM, et al. Detection of Bacillus anthracis spores using terbium dipicolinate photoluminescence. Proc SPIE. 2002.
- Binnemans K. Lanthanide-based luminescent hybrid materials. Chem Rev. 2009;109(9):4283–4374.
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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