View source for Phosphorus-32

{{Short description|Radioactive isotope of phosphorus}}
{{More citations needed|date=December 2022}}
{{Infobox isotope
|image           =
|alternate_names =
|mass_number     = 32
|symbol          = P
|num_neutrons    = 17
|num_protons     = 15
|abundance       = [[trace radioisotope|trace]]
|halflife        = {{val|14.267|u=days}}
|decay_mode1     = [[Beta emission]]
|decay_energy1   = 1.70912
|decay_product   = Sulfur-32
|decay_symbol    = S
|decay_mass      = 32
|mass            = 31.973907274 amu
|spin            =1+
|excess_energy   = {{val|-24304.88}}
|binding_energy  =
}}

'''Phosphorus-32''' (<sup>32</sup>P) is a [[Radionuclide|radioactive isotope]] of [[phosphorus]]. The nucleus of phosphorus-32 contains 15 [[proton]]s and 17 [[neutron]]s, one more neutron than the most common isotope of phosphorus, phosphorus-31. Phosphorus-32 only exists in small quantities on [[Earth]] as it has a short half-life of 14 days and so decays rapidly.

Phosphorus is found in many [[organic molecule]]s, and so, phosphorus-32 has many applications in [[medicine]], [[biochemistry]], and [[molecular biology]] where it can be used to trace phosphorylated molecules (for example, in elucidating [[metabolic pathways]]) and radioactively label [[DNA]] and [[RNA]].

==Decay==
Phosphorus-32 has a short [[half-life]] of 14.268 days and decays into [[sulfur-32]] by [[beta decay]]<ref name="NUBASE2016">{{NUBASE2016}}</ref> as shown in this nuclear equation:
:{| border="0"
|- style="height:2em;"
|{{nuclide|Phosphorus|32}} ||→ ||{{nuclide|Sulfur|32|charge=1+}} ||+ ||{{SubatomicParticle|link=yes|Electron}} ||+ ||{{SubatomicParticle|link=yes|Electron Antineutrino}}
|}
1.709&nbsp;[[MeV]] of energy is released from this decay.<ref name="site.uottawa.ca">{{cite web |url=http://www.site.uottawa.ca:4321/astronomy/index.html#phosphorus32 |title=Phosphorus 32 |website=www.site.uottawa.ca:4321 |archive-url=https://web.archive.org/web/20140222044331/http://www.site.uottawa.ca:4321/astronomy/index.html |archive-date=2014-02-22}}</ref> The kinetic energy of the [[electron]] varies with an average of approximately 0.5&nbsp;MeV and the remainder of the energy is carried by the nearly undetectable [[electron antineutrino]]. In comparison to other beta radiation-emitting nuclides, the electron is moderately energetic. It is blocked by around 1&nbsp;m of air or 5&nbsp;mm of [[acrylic glass]].

The sulfur-32 nucleus produced is in the [[ground state]], so there is no additional [[gamma ray]] emission.

==Production==
{{Expand section|date=March 2011}}
Phosphorus-32 has important uses in [[medicine]], [[biochemistry]] and [[molecular biology]]. It only exists naturally on earth in very small amounts and its short half-life means useful quantities have to be produced synthetically. Phosphorus-32 can be generated synthetically by [[neutron source|irradiation]] of sulfur-32 with moderately fast neutrons as shown in this nuclear equation:
:{| border="0"
|- style="height:2em;"
|{{nuclide|Sulfur|32}} ||+ ||{{SubatomicParticle|link=yes|Neutron}} ||→ ||{{nuclide|Phosphorus|32}} + ||{{SubatomicParticle|link=yes|Proton}}
|}
The sulfur-32 nucleus captures the neutron and emits a proton, reducing the [[atomic number]] by one while maintaining the [[mass number]] of 32.

This reaction has also been used to determine the yield of nuclear weapons.<ref name=Kerr2005>{{cite book |chapter-url=http://www.rerf.or.jp/shared/ds02/pdf/chapter01/cha01-p42-61.pdf |chapter=Bomb Parameters |last1=Kerr |first1=George D. |last2=Young |first2=Robert W. |last3=Cullings |first3=Harry M. |last4=Christy |first4=Robert F. |pages=42–43 |title=Reassessment of the Atomic Bomb Radiation Dosimetry for Hiroshima and Nagasaki – Dosimetry System 2002 |year=2005 |publisher=The Radiation Effects Research Foundation |editor=Robert W. Young, George D. Kerr |access-date=2014-03-13 |archive-date=2015-08-10 |archive-url=https://web.archive.org/web/20150810210007/http://www.rerf.or.jp/shared/ds02/pdf/chapter01/cha01-p42-61.pdf |url-status=dead }}</ref><ref name=Malik1985>{{cite web |url=http://www.osti.gov/manhattan-project-history/publications/LANLHiroshimaNagasakiYields.pdf |title=The Yields of the Hiroshima and Nagasaki Explosions |last=Malik |first=John |date=September 1985 |publisher=Los Alamos National Laboratory |access-date=March 9, 2014}}</ref>

==Uses==
Phosphorus is abundant in biological systems and, as a radioactive isotope, is almost chemically identical with stable isotopes of the same element. Phosphorus-32 can be used to [[radiolabel|label]] biological molecules. The beta radiation emitted by the phosphorus-32 is sufficiently penetrating to be detected outside the organism or tissue which is being analysed

===Biochemistry and molecular biology===
The [[metabolic pathway]]s of organisms extensively use phosphorus in the generation of different biomolecules within the cell. Phosphorus-32 finds use for analysing metabolic pathways in [[pulse chase]] experiments, where a culture of cells is treated for a short time with a phosphorus-32-containing substrate. The sequence of chemical changes, which happen to the substrate, can then be traced by detecting which molecules contain the phosphorus-32 at multiple time points following the initial treatment.

[[DNA]] and [[RNA]] contain a large quantity of phosphorus in the [[phosphodiester]] linkages between [[Nucleobase|bases]] in the [[oligonucleotide]] chain. DNA and RNA can therefore be tracked by replacing the phosphorus with phosphorus-32. This technique is extensively used in [[Southern blot]] and [[Northern blot]] analysis of DNA and RNA samples respectively. In both cases, a phosphorus-32-containing DNA probe hybridises to its complementary sequence, where it appears in a gel. Its location can then be detected by photographic film.

===Plant sciences===
Phosphorus-32 is used in [[plant sciences]] for tracking a plant's uptake of [[fertiliser]] from the [[root]]s to the [[leaves]].  The phosphorus-32-labelled fertiliser is given to the plant [[hydroponic]]ally, or via water in the soil, and the usage of the phosphorus can be mapped from the emitted beta radiation. The information gathered by mapping the [[fertiliser]] uptake shows how the plant takes up and uses the phosphorus from fertiliser.<ref>Singh, B., Singh, J., & Kaur, A. (2013). Applications of Radioisotopes in Agriculture. ''International Journal of Biotechnology and Bioengineering Research,4''(3), 167-174.</ref>

==Safety==
The high energy of emitted beta particles and the low half-life of phosphorus-32 make it potentially harmful; Its molar activity is 338.61&nbsp;TBq/mmol (9151.6&nbsp;Ci/mmol) and its [[specific activity]] is 10.590 EBq/kg (286.22 kCi/g). Typical safety precautions when working with phosphorus-32 include wearing a personal [[dosimeter]] to monitor exposure and an [[Acrylic glass|acrylic]] or [[perspex]] radiation shield to protect the body. Dense shielding, such as lead, is less effective due to the high-energy [[Bremsstrahlung#Beta decay|bremsstrahlung]] produced by the interaction of the beta particle and the shielding. Because the beta radiation from phosphorus-32 is blocked by around 1&nbsp;m of air, it is also advisable to wear dosimeters on the parts of the body, for example the [[finger]]s, which come into close contact with the phosphorus-32-containing sample.

==References==
{{reflist|30em}}

==External links==
* [http://www.nucmedtutorials.com/dwmodesdecay/modes3.html   β- DECAY, β+ DECAY, ELECTRON CAPTURE, & ISOMERIC TRANSITION]
{{Therapeutic radiopharmaceuticals}}

[[Category:Isotopes of phosphorus]]
[[Category:Medical isotopes]]