Pentetic acid

For the diphtheria, tetanus, and acellular pertussis vaccine, see DPT vaccine#DTaP.

Pentetic acid
IUPAC name 2-[Bis[2-[bis(carboxymethyl)amino]ethyl]amino]acetic acid
Other names DTPA; H5dtpa; Diethylenetriaminepentaacetic acid
Identifiers
CAS number	67-43-6 Y
PubChem	3053, 6441444 (Zinc-DTPA)
ChemSpider	2945 Y
UNII	7A314HQM0I
KEGG	D05422 Y
ChEBI	CHEBI:35739 N
ChEMBL	CHEMBL780 Y
RTECS number	MB8205000
Jmol-3D images	Image 1
SMILES C(CN(CC(=O)O)CC(=O)O)N(CCN(CC(=O)O)CC(=O)O)CC(=O)O
InChI InChI=1S/C14H23N3O10/c18-10(19)5-15(1-3-16(6-11(20)21)7-12(22)23)2-4-17(8-13(24)25)9-14(26)27/h1-9H2,(H,18,19)(H,20,21)(H,22,23)(H,24,25)(H,26,27) Y Key: QPCDCPDFJACHGM-UHFFFAOYSA-N Y
Properties
Molecular formula	C14H23N3O10
Molar mass	393.35 g mol−1
Appearance	White crystalline solid
Melting point	220 °C, 493 K, 428 °F
Boiling point	decomposes at a higher temp.
Solubility in water	<0.5 g/100 mL
Hazards
Flash point	Does not burn
Related compounds
Related compounds	EDTA, NTA
N acid (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Pentetic acid or diethylene triamine pentaacetic acid (DTPA) is a polyamino carboxylic acid consisting of a diethylenetriamine backbone with five carboxymethyl groups. The molecule can be viewed as an expanded version of EDTA and it is used similarly.

Coordination properties

The conjugate base of DTPA has a high affinity for metal cations. Thus, the penta-anion DTPA^5- is potentially an octadentate ligand. In contrast, EDTA possesses 6 centres to form coordination bonds with metals.^[1] The formation constants for its complexes are about 100 greater than those for EDTA.^[2]

As a chelating agent, DTPA wraps around a metal ion by forming up to eight bonds. Transition metals, however, usually have a limited coordination capacity and can form less than eight coordination bonds with ligands. So, after forming a complex with a metal, DTPA still has the ability to bind to other reagents, as is shown by its derivative pendetide. For example, in its complex with copper(II), DTPA binds in a hexadentate manner utilizing the three amine centres and three of the five carboxylates.^[3] Like many other chelating agents, DTPA has been considered for treatment of internal contamination from radioactive materials such as plutonium, americium and other actinides. In theory, these complexes are more apt to be eliminated in urine. It is normally administered as the calcium or zinc salt.

Applications

Like the more common EDTA, DTPA is mainly used for sequestering metal ions that otherwise decompose hydrogen peroxide, which is used to bleach pulp in paper making. Several million kilograms are produced for this purpose annually.^[2]

Related compounds

Compounds that are structurally related to DTPA are used in medicine, taking advantage of the high affinity of the triaminopentacarboxylate scaffold for metal ions.

• In ibritumomab tiuxetan, the chelator tiuxetan is a modified version of DTPA whose carbon backbone contains an isothiocyanatobenzyl and a methyl group.^[4]
• In capromab pendetide and satumomab pendetide, the chelator pendetide (GYK-DTPA) is a modified DTPA containing a peptide linker used to connect the chelate to an antibody.^[5]
• Pentetreotide is a modified DTPA attached to a peptide segments.^[6]
• DTPA and derivatives are used to chelate gadolinium to form a MRI contrast agent, such as Magnevist.
• Technetium is chelated with DTPA for ventilation perfusion scan (V/Q scan) and renal scan.^{[citation needed]}

See also

• Nuclear medicine
• Radiopharmaceutical

References

1. ^ Each nitrogen centre counts as a centre of coordination, as does each COO^–-group
2. ^ ^{a b} J. Roger Hart "Ethylenediaminetetraacetic Acid and Related Chelating Agents" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.doi:10.1002/14356007.a10_095
3. ^ Fomenko, et al. Crystal structure of copper (II) diethylenetriaminepentaacetate monohydrate Journal of Structural Chemistry, Vol. 14, Nr. 3 (1973). PDF
4. ^ Milenic, Diane E.; Erik D. Brady, Martin W. Brechbiel (2004-06). "Antibody-targeted radiation cancer therapy". Nat Rev Drug Discov 3 (6): 488–99. doi:10.1038/nrd1413. ISSN 1474-776. PMID 15173838. 
5. ^ Kahn, Daniel; J. Christopher Austin, Robert T Maguire, Sara J Miller, Jack Gerstbrein, Richard D Williams (1999). "A Phase II Study of [90Y] Yttrium-Capromab Pendetide in the Treatment of Men with Prostate Cancer Recurrence Following Radical Prostatectomy". Cancer Biotherapy & Radiopharmaceuticals 14 (2): 99–111. doi:10.1089/cbr.1999.14.99. 
6. ^ Liu, Shuang (2008-09-15). "Bifunctional coupling agents for radiolabeling of biomolecules and target-specific delivery of metallic radionuclides". Advanced Drug Delivery Reviews 60 (12): 1347–70. doi:10.1016/j.addr.2008.04.006. ISSN 0169-409X. PMC 2539110. PMID 18538888. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2539110. 

This article incorporates material from Facts about DTPA, a fact sheet produced by the United States Centers for Disease Control and Prevention.